WO2020140249A1

WO2020140249A1 - A solid fuel package and a solid fuel supply system comprising the same

Info

Publication number: WO2020140249A1
Application number: PCT/CN2019/070338
Authority: WO
Inventors: Mengjia WU; Pascal Metivier; Zhaojia LIN
Original assignee: Rhodia Operations SAS
Current assignee: Rhodia Operations SAS
Priority date: 2019-01-04
Filing date: 2019-01-04
Publication date: 2020-07-09
Anticipated expiration: 2021-07-04

Abstract

A solid fuel package and a solid fuel supply system comprising the solid fuel package. The solid fuel package comprises a container, wherein the container comprises an inlet for a solvent, chambers, a filter and an outlet for a fuel solution in sequence, wherein the number of the chambers is n, n is an integer equal to or greater than 2, an electrolyte is located in Chamber 1 to Chamber n-m which are connected with each other in series, and a solid fuel is located in Chamber n-m+1 to Chamber n which are connected with each other in series, wherein m is an integer, and 1≤m≤n-1.

Description

A solid fuel package and a solid fuel supply system comprising the same

TECHNICAL FIELD

The present invention relates to a solid fuel package and a solid fuel supply system comprising the solid fuel package.

BACKGROUND OF THE INVENTION

Typically, gases (H ₂, O ₂) and liquid solutions of fuels, such as CH ₃OH, HCOOH, CH ₃CH ₂OH, NaBH ₄ are used in fuel cells. For most of them, the natural forms of the fuels at room temperature are gaseous or liquid, such as H ₂, CH ₃OH, HCOOH and CH ₃CH ₂OH. For solid fuels, such as hydrides, formates and hypophosphites, they have to be prepared into a solution in advance and then supplied to fuel cells.

The use of gaseous and liquid fuels is not so convenient for end users in terms of safety, transportation and handling. The highly pressurized H ₂ gas is still not widely accepted owing to the potential safety risk associated to its flammable property. To ensure the safety, very expensive hydrogen tanks must be used to store H ₂ gas. On the other hand, commonly used organic liquid fuels, such as CH ₃OH, HCOOH and CH ₃CH ₂OH, are flammable, toxic and corrosive. And they are forbidden to be taken onto planes. For hydrides, such as NaBH ₄, although this type of fuel is solid, they are very reactive with water and also corrosive. It is impossible for end users to handle the fuel by themselves. All these properties of the above mentioned fuels require careful handling in transportation and in use. Besides, liquid fuels contain large quantity of water as solvent; the increased weight also causes extra expenses in handling and transportation.

JP 2011-60531 mentioned the use of hypophosphites as fuels in direct fuel cells. However, it was claimed that the fuel was supplied to an anode as a solution, wherein the solution consisted of a fuel and water or a hydrophilic organic solvent. That is to say, the fuel was supplied as a liquid to the fuel cells.

In US 6773470 B2, the fuel was supplied in two portions. The first portion was a saturated solution in a polar solvent, such as water; while the second portion was a suspension, which was used as a reservoir. Besides, the fuel composition also included a second fuel, such as alcohols, which was also a liquid. That is to say, the fuel is practically used as a saturated solution or a suspension, which contains water.

There is a need to provide a fuel cell using solid fuels, which is in a package without contacting the solvent in advance. Advantageously, the end users can turn on/off the fuel cell at any time by controlling the supply of the solvent to the package. Conveniently, the transportation of such fuel cell is easier for the users than traditional fuel cells using solid fuels.

It is known to the skilled person that the dissolution of electrolytes, additives or fuels may be highly exothermic, which can cause the decompositions or side-reactions of fuels. The oxidation of fuels before reaching the fuel cells may result in the loss of electricity. In addition, high concentration of fuels, electrolytes, or additives in a small zone may have high viscosity and thus decrease the fluidibility. The present invention develops a solid fuel supply system using solid fuel package and develops a special configuration of package for improving the homogeneity of temperature and concentration, and avoiding decomposition or side-reactions of fuels before the reactions in fuel cell take place.

SUMMARY OF THE INVENTION.

In a first aspect, the present invention relates to a solid fuel package comprising a container, wherein the container comprises an inlet for a solvent, chambers, a filter and an outlet for a fuel solution in sequence, wherein the number of the chambers is n, n is an integer equal to or greater than 2, an electrolyte is located in Chamber 1 to Chamber n-m which are connected with each other in series, and a solid fuel is located in Chamber n-m+1 to Chamber n which are connected with each other in series, wherein m is an integer, and 1≤m ≤n-1.

In a second aspect, the present invention relates to a solid fuel supply system comprising 1) a solvent reservoir containing a solvent, 2) an optional pump, 3) a solid fuel package; and 4) a single fuel cell or a fuel cell stack, wherein the solid fuel package comprising a container, wherein the container comprises an inlet for a solvent, chambers, a filter and an outlet for a fuel solution in sequence, wherein the number of the chambers is n, n is an integer equal to or greater than 2, an electrolyte is located in Chamber 1 to Chamber n-m which are connected with each other in series, and a solid fuel is located in Chamber n-m+1 to Chamber n which are connected with each other in series, wherein m is an integer, and 1≤m ≤n-1.

The solid fuel package or solid fuel supply system of the present application has the following advantages:

1) The solid fuel package or solid fuel supply system of the present application can be used in portable devices (drones) , auxiliary power supply unit (fuel cells) , and big stationary power unit (redox flow battery) , where solid fuels are used;

2) Transportation and distribution of solid fuel packages are much easier than liquids and gases;

3) User friendly–for example, if the solvent for a fuel cell is water, the user’s experience is just like using a coffee capsule; and customers may be able to purchase the capsule in a vendor shop, which largely promotes the use of fuel cells for portable applications.

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1 shows four different configurations 1 (a) , 1 (b) , 1 (c) and 1 (d) of the fuel package.

Fig. 2A illustrates the structure of a solid fuel supply system for fuel cells in which Chamber 1 to Chamber n-m are in series with Chamber n-m+1 to Chamber n.

Fig. 2B illustrates the structure of a solid fuel supply system for fuel cells in which Chamber 1 to Chamber n-m are in parallel with Chamber n-m+1 to Chamber n.

Fig. 3 illustrates the structure of an exemplary single fuel cell.

Fig. 4 illustrates the structure of an exemplary solid fuel package.

Fig. 5 illustrates the structure of another exemplary solid fuel package.

DETAILS OF THE INVENTION

Definitions

Throughout the description, including the claims, the term "comprising one" should be understood as being synonymous with the term "comprising at least one" , unless otherwise specified, and "between" should be understood as being inclusive of the limits.

As used herein, the term “electrolyte” is an ion conducting medium that provides ionic conductivity between the anode and cathode portions of the fuel cell. The electrolyte medium may be any type of media that allows ionic conduction.

As used herein, the term “anode” means the electrode from which electrons migrate to the outside circuit and is the electrode where oxidation occurs.

As used herein, the term “cathode” means the electrode to which electrons migrate from the outside circuit and is the electrode where reduction occurs.

Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of present application to the extent that it may render a term unclear, the present description shall take precedence.

PACKAGE

The present invention relates to a solid fuel package comprising a container, wherein the container comprises an inlet for a solvent, chambers, a filter and an outlet for a fuel solution in sequence, wherein the number of the chambers is n, n is an integer equal to or greater than 2, an electrolyte is located in Chamber 1 to Chamber n-m which are connected with each other in series, and a solid fuel is located in Chamber n-m+1 to Chamber n which are connected with each other in series, wherein m is an integer, and 1≤m≤n-1.

Chambers

Chamber 1, …Chamber n-m are numbered in a direction from the inlet for a solvent to the outlet for the fuel solution.

Chamber n-m+1, …Chamber n are numbered in a direction from the inlet for a solvent to the outlet for the fuel solution.

Preferably, n≤100, or≤50, or≤20. More preferably, n=2, 3, 4, 5, 6, 7, 8, 9 or 10.

Preferably, m=1, 2, 3, 4, 5, 6, 7, 8, or 9.

Chamber 1 to Chamber n-m may be in series with Chamber n-m+1 to Chamber n.

Alternatively, Chamber 1 to Chamber n-m may be in parallel with Chamber n-m+1 to Chamber n.

Different chambers may be separated by a separation element through which the solid fuels, solid electrolyte and solid additives cannot pass, but the solution can pass. The separation element can be a plate, or a film or a seal. It can be fixed at a specific position in the solid fuel package. The separation element usually contains small pores and the mesh size of the separation element should be in the range of 0.1μm to 0.5mm, preferably 1μm to 0.1mm, through which the solid fuels, solid electrolyte and solid additives cannot pass, but the solution can pass. The separation element can be made of rubber, metal, steel, polymers, ceramics, plastics, glass or even filter papers. The separation element can be fixed in the container by any known means, such as welding, bonding and the like, as long as the solid fuels, solid electrolyte and solid additives cannot pass, but the solution can pass and they have sufficient strength to seal and separate different chambers.

Alternatively, the separation element may comprise an opening covered with a permeable material, through which the solid fuels, solid electrolyte and solid additives cannot pass, but the solution can pass is fixed. For example, the material can be a filter paper, filter cloth, a membrane, a sieve, or other types of mesh material.

In another embodiment, the chambers can be separate chambers for the storage of fuel, additives, and electrolytes, without any separation element between them. Each of the separate chambers can be made of a material that is compatible with (or inert to) the fuel, the electrolyte, the solvent and additives. At least the side of the chamber facing the inlet of the solvent and at least the side of the chamber facing the outlet of the fuel solution contain small pores whose diameter should be in the range of 0.1μm to 0.5mm, preferably 1μm to 0.1mm, through which the solid fuels, solid electrolyte and solid additives cannot pass, but the solution can pass. The chambers can be made of rubber, steel, polymers, plastics, ceramics, or glass. Alternatively, at least the side of the chamber facing the inlet of the solvent and at least the side of the chamber facing the outlet of the fuel solution comprise an opening, on which a material through which the solid fuels, solid electrolyte and solid additives cannot pass, but the solution can pass is fixed. For example, the material can be a filter paper, filter cloth, a membrane, a sieve, or other types of mesh material.

Filter

The filter is selected to make sure that solid fuels, solid electrolyte and solid additives cannot pass, but the solution can pass. The filter can be a filter paper, filter cloth, a membrane, a sieve, or other types of mesh element. The mesh size of the filter should be smaller than the particle sizes of the solid powders, which is filled in any of the chambers. The mesh size should be in the range of 0.1μm to 0.5mm, preferably 1μm to 0.1mm, more preferably 1μm to 0.05mm. The filter may be fixed to an opening of a seal.

The filter can be fixed in the container by any known means, such as welding, bonding and the like, as long as the solid fuels, solid electrolyte and solid additives cannot pass, but the solution can pass and they have sufficient strength to seal different chambers.

Container

The container is made of any type of material that is compatible with (or inert to) the fuel, the electrolyte, the solvent and additives. For example, the container can be made of glass, steel, polymers, plastics, ceramics, and the like. The container can be of any shape, for example, the container can be a barrel.

Mixing compartment

Optionally and preferably, there is a mixing compartment after the filter to improve mixing and homogeneity of the fuel solution. The mixing compartment may have a mixing element such as a blade, a stirrer or have some special structural designs to enhance mixing the solution. One design is the blade-type or plate-type mixers inside which different plates or blades are stacked with each other at different angles and another design is helical mixers that is made of a twist helical spirals, other options contains wafer mixers constructed of different plates or blades protruding the inside pipe wall into the flowing fluid at different angel in the direction of flow.

Solid fuels

Solid fuel hereby refers to any type of solid fuels.

The fuel can be an oxidizable compound chosen from the group consisting of phosphorus compound, sulphur compound, nitrogen compound and any combination thereof.

In present invention, oxidizable phosphorus compound, sulphur compound, nitrogen compound may be inorganic or organic compound.

Oxidizable phosphorus compound of present invention may be hypophosphorous acid compounds or phosphorous acid compounds.

Hypophosphorous acid compound of the present invention may be hypophosphorous acid or its derivatives. Hypophosphorous acid derivatives of present invention may notably be salts of hypophosphorous acid.

Examples of hypophosphorous acid salts notably are:

- Alkali metal salts, such as lithium hypophosphite (LiH ₂PO ₂) , sodium hypophosphite (NaH ₂PO ₂) , potassium hypophosphite (KH ₂PO ₂) ;

- Alkaline earth metal salts, such as beryllium hypophosphite (Be (H ₂PO ₂) ₂) , magnesium hypophosphite (Mg (H ₂PO ₂) ₂) , calcium hypophosphite (Ca (H ₂PO ₂) ₂) ;

- Ammonium hypophosphite (NH ₄H ₂PO ₂) .

Among these, lithium hypophosphite (LiH ₂PO ₂) , sodium hypophosphite (NaH ₂PO ₂) , potassium hypophosphite (KH ₂PO ₂) and ammonium hypophosphite (NH ₄H ₂PO ₂) are particularly preferred.

Phosphorous acid compound of the present invention may be phosphorous acid or its derivatives. Phosphorous acid derivatives of present invention may be salts of phosphorous acid.

Examples of phosphorous acid salts notably are:

- Alkali metal salts, such as lithium phosphite (Li ₃PO ₃) , lithium hydrogen phosphite (Li ₂HPO ₃) , lithium dihydrogen phosphite (LiH ₂PO ₃) , sodium phosphite (Na ₃PO ₃) , sodium hydrogen phosphite (Na ₂HPO ₃) , sodium dihydrogen phosphite (NaH ₂PO ₃) , potassium phosphite (K ₃PO ₃) , potassium hydrogen phosphite (K ₂HPO ₃) and potassium dihydrogen phosphite (KH ₂PO ₃) ;

- Alkaline earth metal salts, such as beryllium phosphite (Be ₃ (PO ₃) ₂) , magnesium phosphite (Mg ₃ (PO ₃) ₂) and calcium phosphite (Ca ₃ (PO ₃) ₂) ;

- Ammonium phosphite ( (NH ₄) ₃PO ₃) .

Among these, lithium phosphite (Li ₃PO ₃) , sodium phosphite (Na ₃PO ₃) , potassium phosphite (K ₃PO ₃) and ammonium phosphite ( (NH ₄) ₃PO ₃) are particularly preferred.

Oxidizable sulphur compound of present invention may be sulphurous acid compound or thiosulfuric acid compound.

Sulphurous acid compound of the present invention may be sulphurous acid or its derivatives. Sulphurous acid derivatives of present invention may notably be sulphites.

Examples of sulphites notably are:

- Alkali metal salts, such as lithium sulphite (Li ₂SO ₃) , sodium sulphite (Na ₂SO ₃) and potassium sulphite (K ₂SO ₃) ;

- Alkaline earth metal salts, such as beryllium sulphite (BeSO ₃) , magnesium sulphite (MgSO ₃) and calcium sulphite (CaSO ₃) ;

- Ammonium sulphite ( (NH ₄) ₂SO ₃) .

Among these, lithium sulphite (Li ₂SO ₃) , sodium sulphite (Na ₂SO ₃) , potassium sulphite (K ₂SO ₃) and ammonium sulphite ( (NH ₄) ₂SO ₃) are particularly preferred.

Thiosulfuric acid compound of the present invention may be thiosulfuric acid and its derivatives. Thiosulfuric acid derivatives of present invention may be thiosulfates.

Examples of thiosulfates notably are:

- Alkali metal salts, such as lithium thiosulfate (Li ₂S ₂O ₃) , sodium thiosulfate (Na ₂S ₂O ₃) , potassium thiosulfate (K ₂S ₂O ₃) ;

- Alkaline earth metal salts, such as beryllium thiosulfate (BeS ₂O ₃) , magnesium thiosulfate (MgS ₂O ₃) , calcium thiosulfate (CaS ₂O ₃) ;

- Ammonium thiosulfate ( (NH ₄) ₂ S ₂O ₃) .

Among these, lithium thiosulfate (Li ₂S ₂O ₃) , sodium thiosulfate (Na ₂S ₂O ₃) , potassium thiosulfate (K ₂S ₂O ₃) and ammonium thiosulfate ( (NH ₄) ₂ S ₂O ₃) are particularly preferred.

In present invention, oxidizable nitrogen compound may be nitrous compound or amine.

Nitrous compound of present invention may be nitrous acid or its derivatives. Nitrous acid derivatives of present invention may be salts of nitrous acid.

Example of nitrous acid salts notably are:

- Alkali metal salts, such as lithium nitrite (LiNO ₂) , sodium nitrite (NaNO ₂) and potassium nitrite (KNO ₂) ;

- Alkaline earth metal salts, such as beryllium nitrite (Be (NO ₂) ₂) , magnesium nitrite (Mg (NO ₂) ₂) and calcium nitrite (Ca (NO ₂) ₂) ;

- Ammonium nitrite (NH ₄NO ₂) .

Among these, lithium nitrite (LiNO ₂) , sodium nitrite (NaNO ₂) , potassium nitrite (KNO ₂) and ammonium nitrite (NH ₄NO ₂) are particularly preferred.

Amine of present invention may be ammonia or organic amine, such as alkylamines, arylamines. The fuel can also be an oxidizable compound chosen from the group consisting of hypophosphorous acid salts, borohydride salt, borohydride salt, ammonia borane, formic acid, formate and hydrazine hydrate, and organic chemical hydride.

Examples of borohydride salt notably are:

- Alkali metal salts, such as lithium borohydride (LiBH ₄) , sodium borohydride (Na BH ₄) and potassium borohydride (KBH ₄) ;

- Alkaline earth metal salts, such as beryllium borohydride (Be (BH ₄) ₂) , magnesium borohydride (Mg (BH ₄) ₂) and calcium borohydride (Ca (BH ₄) ₂) .

Examples of formates notably are:

- Alkali metal salts, such as lithium formate (HCOOLi) , sodium formate (HCOONa) and potassium formate (HCOOK) ;

- Alkaline earth metal salts, such as beryllium formate (Be (HCOO) ₂) , magnesium formate (Mg (HCOO) ₂) and calcium formate (Ca (HCOO) ₂) ;

- Ammonium formate (HCOONH ₄) .

Examples of organic chemical hydride notably are:

- Cyclic hydrocarbons, such as cyclohexane, methylcyclohexane, cylohexene, 2-propanol, cyclohexanol, and decalin.

Examples of hypophosphorous acid salts are:

- Ammonium hypophosphite (NH ₄H ₂PO ₂) .

Preferably, the fuel is an oxidizable compound chosen from the group consisting of hypophosphorous acid salts.

It should be understood that the fuel of the present invention may include one or several compounds above mentioned, in which any molar ratio or weight ratio of combinations thereof are contemplated as included within the scope of the invention.

Electrolyte

In the present invention, an electrolyte can be contained in the solid fuel package. Preferred electrolyte is alkali metal hydroxide, such as lithium hydroxide (LiOH) , sodium hydroxide (NaOH) or potassium hydroxide (KOH) , alkali metal bicarbonate, such as sodium bicarbonate (NaHCO ₃) or potassium bicarbonate (KHCO ₃) , alkali metal carbonate, such as lithium carbonate (Li ₂CO ₃) , sodium carbonate (Na ₂CO ₃) or potassium carbonate (K ₂CO ₃) .

The molar ratio of the fuel to the electrolyte can be from 50: 1 to 1: 50, preferably 10: 1 to 1: 10, more preferably 5: 1 to 1: 5, even more preferably 1: 2 to 2: 1.

Additives

Optionally, the fuel package may further comprise additive (s) in any of the chambers. Additives are comprised to avoid competitive reaction or stabilize the fuel, such as thiourea, glycerol, etc. Said competitive reaction particularly refers to hydrogen evolution reaction, which is the production of hydrogen through the process of water electrolysis.

The fuel package can be provided in the form of a capsule or other forms. The fuel package does not contain any solvent; thus an external supply of solvents is needed to connect the fuel package. The fuels, electrolytes and the optional additives are all in the form of solid.

In an exemplary embodiment, the solid fuel package has a structure as shown in Fig. 4. The solid fuel package comprises a fuel container 41, chambers 42, a separation element 43, a filter 44, a solid fuel, such as sodium hypophosphite, electrolyte (s) , such as KOH and optional any suitable additives, and an optional mixing compartment 45. The chambers are separated by the separation element 43. The fuel barrel is the main component of the whole solid fuel package. The fuel barrel can be made of any type of material that is compatible with the solid fuels, electrolyte (s) , solvents and additives. For example, the fuel barrel is made of glass, steel, polymers, ceramics, plastics etc. The electrolytes are in the first three chambers (the figure is just schematic, and the number of the chambers for electrolytes may be 1, 2, 3, 4, …) , the fuels are in the last three chambers (the figure is just schematic the number of the chambers for electrolytes may be 1, 2, 3, 4, …) . The chambers containing the fuels are connected with each other in series, and the chambers containing the electrolytes are connected with each other in series. The chambers containing the fuels are in series with the chambers containing the electrolytes. The optional additives can be in any of the chambers.

In an exemplary embodiment, the solid fuel package has a structure as shown in Fig. 5. The solid fuel package comprises a fuel container 51, chambers 52, a separation element 53, a filter 54, a solid fuel, such as sodium hypophosphite, electrolyte (s) , such as KOH and optional any suitable additives, and an optional mixing compartment 55. The chambers are separated by the separation element 53. The fuel barrel is the main component of the whole solid fuel package. The fuel barrel can be made of any type of material that is compatible with the solid fuels, electrolyte (s) , solvents and additives. For example, the fuel barrel is made of glass, steel, polymers, ceramics, plastics etc. The fuels are in the lower three or more chambers, the electrolytes are in the top three or more chambers. The chambers containing the fuels are connected with each other in series, and the chambers containing the electrolytes are connected with each other in series. The lower chambers containing the fuels are in parallel with the top chambers containing the electrolytes. The optional additives can be in any of the chambers.

SOLID FUEL SUPPLY SYSTEM

The solid fuel supply system of the present application comprises 1) a solvent reservoir containing a solvent, 2) an optional pump, 3) a solid fuel package; and 4) a single fuel cell or a fuel cell stack,

wherein the solid fuel package comprising a container, wherein the container comprises an inlet for a solvent, chambers, a filter and an outlet for a fuel solution in sequence, wherein the number of the chambers is n, n is an integer equal to or greater than 2, an electrolyte is located in Chamber 1 to Chamber n-m which are connected with each other in series, and a solid fuel is located in Chamber n-m+1 to Chamber n which are connected with each other in series, wherein m is an integer, and 1≤m≤n-1.

The solid fuel package is as described previously.

Solvents

The solvent for dissolving the fuel is not particularly limited. Any suitable solvent, such as water and organic solvent can be used. Examples of organic solvent are alcohols, such as methanol, ethanol, n-propanol, and isopropyl alcohol, acetonitrile, DMF, DMSO, CH ₂Cl ₂, THF, NMP, NM, organic carbonates. The solvent is preferably water. It should be understood that the solvent mentioned above can be used independently or in the form of mixtures.

The concentration of the resulting fuel in solution is preferably comprised between 0.01 M and 15 M, preferably 0.1-10M.

Solvent reservoir

Solvent reservoir is used to store the solvent. The reservoir materials can be any type of material that is compatible with fuel, electrolyte and additives; for example, glass, steel, polymers, ceramics, plastics etc.

Pump

Pump is an optional device for driving the solvents to the fuel and electrolyte chambers.

Single fuel cell or fuel cell stack

A single fuel cell may contain fixing end plates, anode/cathode current collectors, a flow field channel, a gasket, and MEAs (Membrane Electrode Assembly) . The fuel cell stack comprises a list of single fuel cells.

The membrane electrode assembly comprises (i) an anode configured and arranged for the oxidation of a reductant, (ii) an ion exchange membrane; and (iii) a cathode configured and arranged for the reduction of an oxidant.

In the present invention, electrode catalyst for anode or cathode may comprise metal element chosen in a group consisting of (i) Transition metals, (ii) Lanthanides, (iii) Actinides, (iv) Elements of Groups IA, IIA, IIIA, IVA, VA, VIA, VIIA of Periodic Table and (v) Any combination thereof.

Specifically, hydrogen is not included in metal element chosen in Group IA of the Periodic Table. Carbon is not included in metal element chosen in Group IVA of the Periodic Table. Nitrogen and phosphorus are not included in metal element chosen in Group VA of the Periodic Table. Oxygen, sulfur and selenium are not included in metal element chosen in Group VIA of the Periodic Table. Fluorine, chlorine, bromine and iodine are not included in metal element chosen in Group VIIA.

The metal elements for the purpose of the present invention are also referred to as metalloids. The term metalloid is generally designating an element which has properties between those of metals and non-metals. Typically, metalloids have a metallic appearance but are relatively brittle and have a moderate electrical conductivity. The six commonly recognized metalloids are boron, silicon, germanium, arsenic, antimony, and tellurium. Other elements also recognized as metalloids include aluminum, polonium, and astatine. On a standard periodic table all of these elements may be found in a diagonal region of the p-block, extending from boron at one end, to astatine at the other (as indicated above) .

Electrode catalyst for anode or cathode of present invention may comprise metal element, which can be in the form of elemental metal, metal alloy, metal oxide or metal complex.

Electrode catalyst for anode or cathode of present invention comprising metal element may be metal oxide compounds comprising typically at least one oxygen atom and at least one metal atom which are chemically bound to the oxygen atom. The metal atom comprised in the metal oxide can be notably transition metal element, post transition metal element, rare earth metal element or metalloid element.

Examples of metal oxide compounds notably are:

- Transition metal oxides, such as: titanium oxide (TiO ₂) , zinc oxide (ZnO) , zirconium oxide (ZrO ₂) and manganese oxide (MnO ₂) .

- Post transition metal oxides, such as: aluminum oxide (Al ₂O ₃) .

- Rare earth element oxides, such as: cerium oxide (CeO ₂) , lanthanium oxide (La ₂O ₃) , praseodymium oxide (Pr ₆O ₁₁) , neodymium oxide (Nd ₂O ₃) , yttrium oxide (Y ₂O ₃) , ruthenium oxide (RuO ₂) , europium oxide (Eu ₂O ₃) and samarium oxide (Sm ₂O ₃) .

- Metalloid element oxides, such as: boron oxide (B ₂O ₃) and silicon oxide (SiO2) .

- Perovskites, such as LaNiO ₃, LaCoO ₃.

The perovskite is any material with the same type of crystal structure as calcium titanium oxide (CaTiO ₃) , known as the perovskite structure, or ^XIIA ^2+VIB ⁴⁺X ^2- ₃ with the oxygen in the face centers, while A and B can also be more than one elements.

Electrode catalyst for anode or cathode of present invention comprising metal element may be metal alloy. The metal alloy may be notably selected from the group consisting of Pt-Au, Pd-Au, Pt-Pd, Pd-Ni, Pt-Ni, Pt-Ru, Pd-Ru and Pt-Sn alloys.

In one embodiment, catalyst for anode or cathode of present invention comprising metal element may further comprise non-metal elements, such as C, N and P. For example, non-metal element can be doped in the metal catalyst.

Electrode catalyst for anode or cathode of present invention may also comprise non-metal element chosen in a group consisting of elements of Groups IA, IVA, VA, VIA, VIIA of Periodic Table or any combination thereof. Said catalyst preferably comprises non-metal elements, such as C, N and P and combinations thereof. More preferable catalyst comprising of non-metal elements is N-doped C or S-doped C.

In present invention, anode catalyst may preferably comprise element chosen in a group consisting of elements of Groups IIIA, IVA, VA of Periodic Table and Transition metals.

Examples of anode catalyst notably are:

- Elemental metal comprise element chosen in a group consisting of Pd, Pt, Ru, Au, Rh, Ir, Bi, Sn, B and any combination thereof.

- Metal alloy, such as Pd-Au, Pd-B and Pt-Ru.

In present invention, cathode catalyst may preferably comprise element chosen in a group consisting of elements of Groups IA, IIA, IIIA, IVA, VA, VIA, VIIA of Periodic Table, Transition metals and Lanthanides.

Examples of cathode catalyst notably are:

- Elemental metal comprise element chosen in a group consisting of Ag, Ni, Ru, Ir, Os, Mn, La, Co, Ce and any combination thereof.

- Metal oxide, such as manganese oxide (MnO ₂) , ruthenium oxide (RuO ₂) , cerium oxide (CeO) , europium oxide (Eu ₂O ₃) , samarium oxide (Sm ₂O ₃) , cobalt oxide (CoO) , cobaltic oxide (Co ₃O ₄) , Perovskites, such as LaNiO ₃, LaCoO ₃ and any combination thereof.

- Non-metal compound, such as N-doped C and S-doped C.

It should be understand by the people skilled in the art that the electrode catalyst for anode or cathode mention above can be loaded on a support. The supports applied are not particularly limited. Typical example of supports can be carbon, alumina and silica.

In one embodiment, the electrode may comprise catalyst mentioned above and a substrate.

Preferably, the anode and cathode can be made with porous substrate structures. The anode substrates may comprise one or more conducting materials prepared in a sheet, foam, grid, cloth or other similar conductive and porous structure. The substrate can be chemically passive, and merely physically support the anode catalyst and transmit electrons, and/or it can be chemically or electrochemically active, assisting in the anode reaction, in pre-conditioning of fuel, in post-conditioning of anode reaction products, in physical control of the location of the electrolyte and other fluids, and/or in other similarly useful processes. Anode substrates can include, for example, stainless steel net, nickel foam, sintered nickel powder, etched aluminum-nickel mixtures, carbon fibers, and carbon cloth. Preferably, carbon materials and stainless steel are used as an anode substrate.

The cathode substrates may comprise one or more conducting materials prepared in a sheet, foam, grid, cloth or other similar structure. The cathode substrate can be chemically passive, and merely physically support the cathode catalyst and transmit electrons, and/or it can be chemically or electrochemically active, assisting in the cathode reaction, in pre-conditioning of fuel, in post-conditioning of cathode reaction products, in physical control of the location of the electrolyte and other fluids, and/or in other similarly useful processes. Cathode substrates can include stainless steel, nickel foam, sintered nickel powder, etched aluminum-nickel mixtures, metal screens, carbon fibers, and carbon cloth.

Methods for applying the anode catalysts to the anode substrate and cathode catalysts to the cathode substrate include, for example, spreading, wet spraying, powder deposition, electro-deposition, evaporative deposition, dry spraying, decaling, painting, sputtering, low pressure vapor deposition, electrochemical vapor deposition, tape casting, screen printing, hot pressing and other methods.

When electrode substrates are used, the preferred range of catalyst loading amount may be comprised between 0.01 and 500 mg/cm ^-2. More preferably, the catalyst loading amount may be comprised between 1 and 20 mg/cm ^-2.

In one embodiment, an ion exchange membrane is used. The ion exchange membrane can be an anion exchange membrane or a cation exchange membrane. Preferably, the ion exchange membrane is an anion exchange membrane.

In another preferred embodiment, anode and cathode reside in two independent apartments, where a separator can be placed between the two compartments. As used herein "separator" should be understood as a layer that provides a physical separation between the anode and the cathode and acts as an electrical insulator between the two conductive electrodes. It has pores big enough for the fuel or electrolyte solution to go through. In this equipment, reductant and oxidant may exist in two compartments. But it’s still possible for reductant and oxidant freely to communicate between the anode and cathode.

The difference between separator and ion-exchange membrane is that it is not selective to ions and it allows fuel molecules to flow freely between the anode and the cathode. Because of this difference, the separator is much cheaper and much less resistive than the ion-exchange membrane.

The materials of separator are not particularly limited. Examples of separators include dielectric materials such as nonwoven fibers like cotton, nylon, polyesters, glass, polymer like polyethylene, polypropylene, poly (tetrafluoroethylene) , polyvinyl chloride or naturally occurring substances like rubber, asbestos, wood.

Separators can consist of a single or multiple layers/sheets of same or different materials. In present invention, if a separator is used, the distance between the two electrodes may be in a range of 0.1 to 10 cm and preferably in a range of 0.2 to 2 cm. In one embodiment, the present invention is a fuel cell comprising an anode and a cathode made with substrates and porous separator. For example, anode and cathode made with substrates are pressed to each side of the separator so it makes an electrode assembly or separator can be only disposed between the anode and cathode.

All typical methods for preparing an electrode assembly can be applied in the present application, such as those mentioned in “Principles of MEA preparation” , from “Handbook of Fuel Cells-Fundamentals, Technology and Applications” , edited by Wolf Vielstich, Hubert A. Gasteiger, Arnold Lamm and Harumi Yokokawa@2010 John Wiley&Sons, Ltd. ISBN: 978-0-470-97400-1.

Fig. 3 shows the structure of an exemplary single fuel cell. The single fuel cell comprises fixing end plates 31, anode current collector and fuel channel 32, a gasket 33, an anode catalyst layer 34, a membrane or a separator 35, a cathode catalyst layer 36, cathode current collector and fuel channel 37.

Fig. 2A illustrates the structure of an exemplary solid fuel supply system for fuel cells. It comprises 1) a solvent reservoir 22 containing a solvent, 2) an optional pump 24, 3) a solid fuel package 23; and 4) a fuel cell stack 21, wherein the solid fuel package comprising a container, wherein the container comprises an inlet for a solvent, chambers, a filter, an optional mixing compartment and an outlet for a fuel solution in sequence, wherein the number of the chambers is n, n is an integer equal to or greater than 2, an electrolyte is located in Chamber 1 to Chamber n-m which are connected with each other in series, and a solid fuel is located in Chamber n-m+1 to Chamber n which are connected with each other in series, wherein m is an integer, and 1≤m≤n-1, and Chamber 1 to Chamber n-m are in series with Chamber n-m+1 to Chamber n.

Fig. 2B illustrates the structure of an exemplary solid fuel supply system for fuel cells. It comprises 1) a solvent reservoir 22’ containing a solvent, 2) an optional pump 24’, 3) a solid fuel package 23’; and 4) a fuel cell stack 21’, wherein the solid fuel package comprising a container, wherein the container comprises an inlet for a solvent, chambers, a filter, an optional mixing compartment and an outlet for a fuel solution in sequence, wherein the number of the chambers is n, n is an integer equal to or greater than 2, an electrolyte is located in Chamber 1 to Chamber n-m which are connected with each other in series, and a solid fuel is located in Chamber n-m+1 to Chamber n which are connected with each other in series, wherein m is an integer, and 1≤m≤n-1, and Chamber 1 to Chamber n-m are in parallel with Chamber n-m+1 to Chamber n.

The following examples are included to illustrate embodiments of the invention. Needless to say, the invention is not limited to the described examples.

EXAMPLES

EXAMPLES FOR THE SOLID FUEL PACKAGE

³¹P NMR analysis for calculating the constitution of the fuel solution at outlet

³¹P NMR spectra were recorded on Bruker AVIII spectrometers at 300MHz for ³¹P IG (Inverse Gated Decoupling) . The chemical shift of the hypophosphite (P ⁺¹) and its two oxidation compounds (P ⁺³and P ⁺⁵) in strongly alkaline solution are listed as below. The reference of the chemical shifts is 85%phosphoric acid (recorded by instrument after once) . The small resonances symmetrically distributed around main peaks in decoupled spectra were residual coupling. This phenomenon is caused by large P-H coupling constant and can be removed in coupled spectra. The conversion of hypophosphite (P ⁺¹) is calculated by the area of corresponding peaks of each P species.

NaH ₂PO ₂ (P ^I) : ³¹P-NMR (IG, 300 MHz, D ₂O) : δ=7.7;

Na ₂HPO ₃ (P ^III) : ³¹P-NMR (IG, 300 MHz, D ₂O) : δ=3.5;

Na ₃PO ₄ (P ^V) : ³¹P-NMR (IG, 300 MHz, D ₂O) : δ=5.3

The conversion of hypophosphite (P ⁺¹) can be calculated by:

where X _i stands for the conversion of hypophosphite (P ⁺¹) at the outlet of solid fuel package

P ⁱ stands for any phosphor species in the solution at the outlet of solid fuel package.

Example 1

Test of different configurations of solid fuel packages.

In this example, four different configurations of solid fuel capsules were assembled, as shown in Fig. 1 (a) ～ (d) , and the composition of liquid fuels at the outlet of solid fuel package were analyzed by ³¹P NMR. The concentration of the fuel was designed to be 0.5 M sodium hypophosphite (NaH ₂PO ₂) aqueous solution with 1.0 M potassium hydroxide as an optional supporting electrolyte. This formulation was reported in the prior art to be one of the optimized concentrations for the best cell performances.

In Fig. 1 (a) , the solid fuel package was composed of fuel barrel, filter, and a solid fuel, sodium hypophosphite solid powders (NaH ₂PO ₂) . The mentioned fuel barrel was a 100 ml plastic syringe with only one chamber. The tip of the syringe was used as the inlet of the solid fuel package, while the other end of the syringe was used as the outlet of the solid fuel package. The filter used here was a filter paper (Whatman filter paper 540) covered on a seal. Then the seal was pushed into the barrel, with the filter paper facing inside of the fuel barrel. The seal used here was a rubber stopper taken from the tip of the plunger of the syringe. To allow the liquid flowing through the rubber stopper, a round-shaped opening with a diameter of 5 mm was carefully cut in the middle of the rubber stopper. 2.65 g of sodium hypophosphite was weighed and placed inside of the fuel barrel. 49 ml of ultrapure water was poured into the solvent reservoir (22) , as shown in Fig. 2A. Water was driven by a peristaltic pump (Masterflex) (24) as shown in Fig. 2A to the solid fuel package at a flow rate of 5 ml/min, and gradually dissolved NaH ₂PO ₂ solid powders and then NaH ₂PO ₂ aqueous solution passed through filter and was collected at the outlet of the package for ³¹P NMR measurement. The temperature of the collected solution was also measured by a digital thermometer (KT300) .

In Fig. 1 (b) , the solid fuel package was composed of fuel barrel, filter, a solid fuel, sodium hypophosphite powders (NaH ₂PO ₂) and an electrolyte, potassium hydroxide (KOH) . The mentioned fuel barrel was a 100 ml plastic syringe with only one chamber. The tip of the syringe was used as the inlet of the solid fuel package, while the other end of the syringe was used as the outlet of the solid fuel package. The filter used here was a filter paper (Whatman filter paper 540) covered on a seal. Then the seal was pushed into the barrel, with the filter paper facing inside of the fuel barrel. The seal used here was a rubber stopper taken from the tip of the plunger of the syringe. To allow the liquid flowing through the rubber stopper, a round-shaped opening with a diameter of 5 mm was carefully cut in the middle of the rubber stopper. 2.65 g of sodium hypophosphite (NaH ₂PO ₂) and 2.81 g of potassium hydroxide (KOH) were weighed, mixed and placed inside of the fuel barrel. 49 ml of ultrapure water was poured into the solvent reservoir (22) , as shown in Fig. 2A. Water was driven by a peristaltic pump (Masterflex) (24) as shown in Fig. 2A to the solid fuel package at a flow rate of 5 ml/min, and gradually dissolved NaH ₂PO ₂ and KOH solid-powder mixture and then NaH ₂PO ₂ alkaline solution passed through filter and was collected at the outlet of the package for ³¹P NMR measurement. The temperature of the collected solution was also measured by a digital thermometer (KT300) .

In Fig. 1 (c) , the solid fuel package was composed of fuel barrel, separation element, filter, a solid fuel, sodium hypophosphite powders (NaH ₂PO ₂) and an electrolyte, potassium hydroxide (KOH) . The mentioned fuel barrel was a 100 ml plastic syringe with two chambers, which were separated by the separation element and connected in series. The tip of the syringe was used as the inlet of the solid fuel package, while the other end of the syringe was used as the outlet of the solid fuel package. The first chamber of the solid fuel package, which was in direct connection with the inlet of the package, contained 2.81 g of potassium hydroxide (KOH) . The first chamber was then separated by a separation element which is a filter paper (Whatman filter paper 540) covered on a seal. Then the seal was pushed into the barrel, with the filter paper facing inside of the fuel barrel. The seal used here was a rubber stopper taken from the tip of the plunger of the syringe. To allow the liquid flowing through the rubber stopper, a round-shaped opening with a diameter of 15 mm was carefully cut in the middle of the rubber stopper. The second chamber of the solid fuel package, which was in direct connection with the outlet of the package, contained 2.65 g of sodium hypophosphite. The second chamber was then connected to the filter which used a filter paper (Whatman filter paper 540) covered on a seal. Then the seal was pushed into the barrel, with the filter paper facing inside of the fuel barrel. The seal used here was a rubber stopper taken from the tip of the plunger of the syringe. To allow the liquid flowing through the rubber stopper, a round-shaped opening with a diameter of 5 mm was carefully cut in the middle of rubber stopper. 49 ml of ultrapure water was poured into the solvent reservoir (22) , as shown in Fig. 2A. Water was driven by a peristaltic pump (Masterflex) (24) as shown in Fig. 2A to the solid fuel package at a flow rate of 5 ml/min, and gradually dissolved KOH and NaH ₂PO ₂ solid powders and then NaH ₂PO ₂ alkaline solution passed through second filter and was collected at the outlet of the package for ³¹P NMR measurement. The temperature of the collected solution was also measured by a digital thermometer (KT300) .

In Fig. 1 (d) , the solid fuel package was composed of fuel barrel, separation element, filter, a solid fuel, sodium hypophosphite powders (NaH ₂PO ₂) and an electrolyte, potassium hydroxide (KOH) . The mentioned fuel barrel was a 100 ml plastic syringe with two chambers, which were separated by a separation element and connected in series. The tip of the syringe was used as the inlet of the solid fuel package, while the other end of the syringe was used as the outlet of the solid fuel package. The first chamber of the solid fuel package, which was in direct connection with the inlet of the package, contained 2.65 g of sodium hypophosphite. The first chamber was then separated by a separation element which is a filter paper (Whatman filter paper 540) covered on a seal. Then the seal was pushed into the barrel, with the filter paper facing inside of the fuel barrel. The seal used here was a rubber stopper taken from the tip of the plunger of the syringe. To allow the liquid flowing through the rubber stopper, a round-shaped opening with a diameter of 15 mm was carefully cut in the middle of the rubber stopper. The second chamber of the solid fuel package, which was in direct connection with the outlet of the package, contained 2.81 g of potassium hydroxide (KOH) . The second chamber was then connected to the filter which used a filter paper (Whatman filter paper 540) covered on a seal. Then the seal was pushed into the barrel, with the filter paper facing inside of the fuel barrel. The seal used here was a rubber stopper taken from the tip of the plunger of the syringe. To allow the liquid flowing through the rubber stopper, a round-shaped opening with a diameter of 5 mm was carefully cut in the middle of the rubber stopper. 49 ml of ultrapure water was poured into the solvent reservoir (22) , as shown in Fig. 2A. Water was driven by a peristaltic pump (Masterflex) (24) as shown in Fig. 2A to the solid fuel package at a flow rate of 5 ml/min, and gradually dissolved NaH ₂PO ₂ and KOH solid powders and then NaH ₂PO ₂ alkaline solution passed through second filter and was collected at the outlet of the package for ³¹P NMR measurement. The temperature of the collected solution was also measured by a digital thermometer (KT300) .

Table 1 Summary of monitored temperature and conversion of sodium hypophosphite in the four different designs of solid fuel package from Example 1

The results of monitored temperature and conversion of sodium hypophosphite were summarized in Table 1. The results suggested that design in Fig. 1 (c) was the best configuration for supplying NaH ₂PO ₂ and KOH solid powders in a solid fuel package.

Example 2

Test of different ratios of sodium hypophosphite to potassium hydroxide in Design Fig. 1 (c)

In this example, the solid fuel package was composed of a fuel barrel, a seal, a filter, a solid fuel, sodium hypophosphite powders (NaH ₂PO ₂) and an electrolyte, potassium hydroxide (KOH) . The mentioned fuel barrel was a 100 ml plastic syringe with two chambers, which were separated by rubber stoppers and connected in series. The tip of the syringe was used as the inlet of the solid fuel package, while the other end of the syringe was used as the outlet of the solid fuel package. The first chamber of the solid fuel package, which was in direct connection with the inlet of the package, contained potassium hydroxide (KOH) . The first chamber was then separated by a separation element which is a filter paper (Whatman filter paper 540) covered on a seal. Then the seal was pushed into the barrel, with the filter paper facing inside of the fuel barrel. The seal used here was a rubber stopper taken from the tip of the plunger of the syringe. To allow the liquid flowing through the rubber stopper, a round-shaped opening with a diameter of 15 mm was carefully cut in the middle of the rubber stopper. The second chamber of the solid fuel package, which was in direct connection with the outlet of the package, contained sodium hypophosphite. The second chamber was then connected to the filter which used a filter paper (Whatman filter paper 540) covered on a seal. Then the seal was pushed into the barrel, with the filter paper facing inside of the fuel barrel. The seal used here was a rubber stopper taken from the tip of the plunger of the syringe. To allow the liquid flowing through the rubber stopper, a round-shaped opening with a diameter of 5 mm was carefully cut in the middle of the rubber stopper. 49 ml of ultrapure water was poured into the solvent reservoir (22) , as shown in Fig. 2A. Water was driven by a peristaltic pump (Masterflex) (4) in Fig. 2A to the solid fuel package at a flow rate of 5 ml/min, and gradually dissolved KOH and NaH ₂PO ₂ solid powders and then NaH ₂PO ₂ alkaline solution passed through second filter and was collected at the outlet of the package for ³¹P NMR measurement. The temperature of the collected solution was also measured by a digital thermometer (KT300) .

Three different formulations were tested in this type of solid fuel package, which were summarized in Table 2.

In the first formulation, 2.81 g of potassium hydroxide (KOH) was weighed and placed in the first chamber, while 2.65 g of sodium hypophosphite (NaH ₂PO ₂) was also weighed and placed in the second chamber. The above fuel and base can reach a concentration ratio of 1: 2 for sodium hypophosphite (NaH ₂PO ₂) to potassium hydroxide (KOH) .

In the second formulation, 2.81 g of potassium hydroxide (KOH) was weighed and placed in the first chamber, while 5.30 g of sodium hypophosphite (NaH ₂PO ₂) was also weighed and placed in the second chamber. The above fuel and base can reach a concentration ratio of 1: 1 for sodium hypophosphite (NaH ₂PO ₂) to potassium hydroxide (KOH) .

In the third formulation, 2.81 g of potassium hydroxide (KOH) was weighed and placed in the first chamber, while 10.60 g of sodium hypophosphite (NaH ₂PO ₂) was also weighed and placed in the second chamber. The above fuel and base can reach a concentration ratio of 2: 1 for sodium hypophosphite (NaH ₂PO ₂) to potassium hydroxide (KOH) .

The results of monitored temperature and conversion of sodium hypophosphite were summarized in Table 2. The results suggested that under this type of configuration, no fuel oxidation was detected by ³¹P NMR, therefore it was the best configuration which can be used in different formulations. Furthermore, there was no sharp temperature increase during dissolution of solids in the fuel package; therefore, it was also safer for heat management.

Table 2 Summary of monitored temperature and conversion of sodium hypophosphite at different ratios of sodium hypophosphite to potassium hydroxide in the design of Fig. 1 (c) from Example 1

EXAMPLES FOR THE FUEL CELL SUPPLY SYSTEM

Example 3 low concentration

In this example, Pd black and Pt black were used as anode and cathode catalyst, respectively, in a single fuel cell. Pd black coated gas diffusion layer (Pd-GDL) and Pt black coated gas diffusion layer (Pt-GDL) were supplied by FuelCellsEtc with a surface area of 3.5 x 3.5 cm ². The loading of Pd black and Pt black on GDL was 2 mg/cm ². The Membrane Electrode Assembly (MEA) was assembled by stacking the Pd-GDL, Anion Exchange Membrane (AEM, FAA-3, Fumatech) and Pt-GDL. The size of the AEM is 5 x 5 cm ².

Ultrapure water was used as solvent, and 49 ml of ultrapure water was poured into the solvent reservoir.

Sodium hypophosphite (NaH ₂PO ₂) and pottasium hydroxide (KOH) solid powders were charged into the fuel package as shown in Fig. 1 (c) , which has two chambers, KOH was charged into the first chamber, while NaH ₂PO ₂was charged into the second chamber. To reach a concentration of 0.1 mol/L NaH ₂PO ₂ solution in 1.0 mol/L KOH solution, 0.53 g of NaH ₂PO ₂ and 2.81 g of KOH were charged into the fuel package. The first chamber was then separated by a separation element which is a filter paper (Whatman filter paper 540) covered on a seal. Then the seal was pushed into the barrel, with the filter paper facing inside of the fuel barrel. The seal used here was a rubber stopper taken from the tip of the plunger of the syringe. To allow the liquid flowing through the rubber stopper, a round-shaped opening with a diameter of 15 mm was carefully cut in the middle of the rubber stopper. The second chamber of the solid fuel package, which was in direct connection with the outlet of the package, contained sodium hypophosphite. The second chamber was then connected to the filter which used a filter paper (Whatman filter paper 540) covered on a seal. Then the seal was pushed into the barrel, with the filter paper facing inside of the fuel barrel. The seal used here was a rubber stopper taken from the tip of the plunger of the syringe. To allow the liquid flowing through the rubber stopper, a round-shaped opening with a diameter of 5 mm was carefully cut in the middle of the rubber stopper.

Water was stored in the solvent reservoir. A pump was connected between the solvent reservoir and the solid fuel package. The electricity of the pump was turned on. Water was driven by the pump to the solid fuel package, and gradually dissolved the solid fuels. Then NaH ₂PO ₂ solution passed the filter of the solid fule package and was fed into the fuel cell. The outlet of the fuel solution from fuel cell was circulated back to the solvent reservoir. The flow rate of air was controlled by a flow meter at 100 ml/min at a pressure of 1 bar. The open circuit potential and power density of the fuel cell were recorded by potentiostat/gavalnostat (Gamry Reference 3000) at room temperature. The open circuit pot1ential and peak power density were recorded and summarized in Table 3. As shown in the table, the performances of the present fuel supply system is comparable to a fuel cell directly using a fuel solution.

Comparative example 3:

In this example, Pd black and Pt black were used as anode and cathode catalyst, respectively. Pd black coated gas diffusion layer (Pd-GDL) and Pt black coated gas diffusion layer (Pt-GDL) were supplied by FuelCellsEtc with a surface area of 3.5 x 3.5 cm ². The loading of Pd black and Pt black on GDL was 2 mg/cm ². The Membrane Electrode Assembly (MEA) was assembled by stacking the Pd-GDL, Anion Exchange Membrane (AEM, FAA-3, Fumatech) and Pt-GDL. The size of the AEM is 5 x 5 cm ².

The testing fuels were prepared by dissolving NaH ₂PO ₂ and KOH into ultrapure water. NaH ₂PO ₂ concentrations of 0.1 mol/L were prepared in this example with addition of 1.0 M KOH as supporting electrolyte. Specifically, 1.06 g of NaH ₂PO ₂ and 5.61 g of KOH were weighed and dissolved into 100 ml ultrapure water to make 0.1 mol/L NaH ₂PO ₂ alkaline solution.

Conventional fuel cell testing hardware with active surface area of 12.25 cm ² was used for fuel cell performance test. The flow rate of anode fuel was controlled by a peristaltic pumps (supplied by Masterflex) at a flow rate of 5 ml/min. The flow rate of air was controlled by a flow meter at 100 ml/min at a pressure of 1 bar. The open circuit potential and power density of the fuel cell were recorded by potentiostat/gavalnostat (Gamry Reference 3000) at room temperature. The open circuit potential and maximal power density are 1.03V and 29.6 mW/cm ², as summarized in Table 3.

Table 3 Summary of fuel cell performance at 0.1 M sodium hypophosphite with different fuel supply methods

Example 4 medium concentration

The set up used in this example is the same as that mentioned in example 1. In this example, Pd black and Pt black were used as anode and cathode catalyst, respectively, in a single fuel cell. Pd black coated gas diffusion layer (Pd-GDL) and Pt black coated gas diffusion layer (Pt-GDL) were supplied by FuelCellsEtc with a surface area of 3.5 x 3.5 cm ². The loading of Pd black and Pt black on GDL was 2 mg/cm ². The Membrane Electrode Assembly (MEA) was assembled by stacking the Pd-GDL, Anion Exchange Membrane (AEM, FAA-3, Fumatech) and Pt-GDL. The size of the AEM is 5 x 5 cm ².

Ultrapure water was used as solvent, and 40 ml of ultrapure water was poured into the solvent reservoir.

Sodium hypophosphite (NaH ₂PO ₂) and pottasium hydroxide (KOH) solid powders were charged into the fuel package as shown in Fig. 1 (c) , which has two chambers, KOH was charged into the first chamber, while sodium hypophosphite was charged into the second chamber. To reach a concentration of 5.0 mol/L NaH ₂PO ₂ solution in 1.0 mol/L KOH solution, 26.5 g of NaH ₂PO ₂ and 2.81 g of KOH were charged into the fuel package. The first chamber was then separated by a separation element which is a filter paper (Whatman filter paper 540) covered on a seal. Then the seal was pushed into the barrel, with the filter paper facing inside of the fuel barrel. The seal used here was a rubber stopper taken from the tip of the plunger of the syringe. To allow the liquid flowing through the rubber stopper, a round-shaped opening with a diameter of 15 mm was carefully cut in the middle of the rubber stopper. The second chamber of the solid fuel package, which was in direct connection with the outlet of the package, contained sodium hypophosphite. The second chamber was then connected to the filter which used a filter paper (Whatman filter paper 540) covered on a seal. Then the seal was pushed into the barrel, with the filter paper facing inside of the fuel barrel. The seal used here was a rubber stopper taken from the tip of the plunger of the syringe. To allow the liquid flowing through the rubber stopper, a round-shaped opening with a diameter of 5 mm was carefully cut in the middle of the rubber stopper.

Water was stored in the solvent reservoir. A pump was connected between the solvent reservoir and the solid fuel package. The electricity of the pump was turned on. Water was driven by the pump to the solid fuel package, and gradually dissolved the solid fuels. Then NaH ₂PO ₂ solution passed the filter of the solid fule package and was fed into the fuel cell. The outlet of the fuel solution from fuel cell was circulated back to the solvent reservoir. The flow rate of air was controlled by a flow meter at 100 ml/min at a pressure of 1 bar. The open circuit potential and power density of the fuel cell were recorded by potentiostat/gavalnostat (Gamry Reference 3000) at room temperature. The open circuit pot1ential and peak power density were recorded and summarized in Table 4. As shown in the table, the performances of the present fuel supply system is comparable to a fuel cell directly using a fuel solution.

Comparative example 4:

The testing fuels were prepared by dissolving NaH ₂PO ₂ and KOH into ultrapure water. NaH ₂PO ₂ concentrations of 5.0 mol/L were prepared in this example with addition of 1.0 M KOH as supporting electrolyte. Specifically, 53.0 g of NaH ₂PO ₂ and 5.61 g of KOH were weight and dissolved into 100 ml ultrapure water to make 5.0 mol/L NaH ₂PO ₂ alkaline solution under magnetic stirring at 300 rpm for 60 mins.

Conventional fuel cell testing hardware with active surface area of 12.25 cm ² was used for fuel cell performance test. The flow rate of anode fuel was controlled by a peristaltic pumps (supplied by Masterflex) at a flow rate of 5 ml/min. The flow rate of air was controlled by a flow meter at 100 ml/min at a pressure of 1 bar. The open circuit potential and power density of the fuel cell were recorded by potentiostat/gavalnostat (Gamry Reference 3000) at room temperature. The open circuit potential and maximal power density are 0.83 V and 5.6 mW/cm ², as summarized in Table 4.

Table 4 Summary of fuel cell performance at 5.0 M sodium hypophosphite with different fuel supply methods

Example 5 saturated concentration

Ultrapure water was used as solvent, and 30 ml of ultrapure water was poured into the solvent reservoir.

Sodium hypophosphite (NaH ₂PO ₂) and pottasium hydroxide (KOH) solid powders were charged into the fuel package as shown in Fig. 1 (c) , which has two chambers, KOH was charged into the first chamber, while sodium hypophosphite was charged into the second chamber. To reach a concentration of 8.0 mol/L NaH ₂PO ₂ solution in 1.0 mol/L KOH solution, 42.4 g of NaH ₂PO ₂ and 2.81 g of KOH were charged into the fuel package. The first chamber was then separated by a separation element which is a filter paper (Whatman filter paper 540) covered on a seal. Then the seal was pushed into the barrel, with the filter paper facing inside of the fuel barrel. The seal used here was a rubber stopper taken from the tip of the plunger of the syringe. To allow the liquid flowing through the rubber stopper, a round-shaped opening with a diameter of 15 mm was carefully cut in the middle of the rubber stopper. The second chamber of the solid fuel package, which was in direct connection with the outlet of the package, contained sodium hypophosphite. The second chamber was then connected to the filter which used a filter paper (Whatman filter paper 540) covered on a seal. Then the seal was pushed into the barrel, with the filter paper facing inside of the fuel barrel. The seal used here was a rubber stopper taken from the tip of the plunger of the syringe. To allow the liquid flowing through the rubber stopper, a round-shaped opening with a diameter of 5 mm was carefully cut in the middle of the rubber stopper.

Water was stored in the solvent reservoir. A pump was connected between the solvent reservoir and the solid fuel package. The electricity of the pump was turned on. Water was driven by the pump to the solid fuel package, and gradually dissolved the solid fuels. Then NaH ₂PO ₂ solution passed the filter of the solid fule package and was fed into the fuel cell stack. The outlet of the fuel solution from fuel cell was circulated back to the solvent reservoir. The flow rate of air was controlled by a flow meter at 100 ml/min at a pressure of 1 bar. The open circuit potential and power density of the fuel cell were recorded by potentiostat/gavalnostat (Gamry Reference 3000) at room temperature. The open circuit pot1ential and peak power density were recorded and summarized in Table 5. As shown in the table, the performances of the present fuel supply system is comparable to a fuel cell directly using a fuel solution.

Comparative example 5:

The testing fuels were prepared by dissolving NaH ₂PO ₂ and KOH into ultrapure water. NaH ₂PO ₂ concentrations of 8.0 mol/L were prepared in this example with addition of 1.0 M KOH as supporting electrolyte. Specifically, 84.80 g of NaH ₂PO ₂ and 5.61 g of KOH were weight and dissolved into 100 ml ultrapure water to make 8.0 mol/L NaH ₂PO ₂ alkaline solution under magnetic stirring at 300 rpm for 120 mins and ultrasonication for 30 mins.

Conventional fuel cell testing hardware with active surface area of 12.25 cm ² was used for fuel cell performance test. The flow rate of anode fuel was controlled by a peristaltic pumps (supplied by Masterflex) at a flow rate of 5 ml/min. The flow rate of air was controlled by a flow meter at 100 ml/min at a pressure of 1 bar. The open circuit potential and power density of the fuel cell were recorded by potentiostat/gavalnostat (Gamry Reference 3000) at room temperature. The open circuit potential and maximal power density are 0.49 V and 3.7 mW/cm ², as summarized in Table 5.

Table 5 Summary of fuel cell performance at 8.0 M sodium hypophosphite with different fuel supply methods

The comparision betwee Examples 3-5 and Comparative Example 3-5 show that the use of a solid fuel package of the present application can obtain a similar open circuit potential and power density (mW/cm ²) to the use of a fuel solution.

Claims

A solid fuel package comprising a container, wherein the container comprises an inlet for a solvent, chambers, a filter and an outlet for a fuel solution in sequence, wherein the number of the chambers is n, n is an integer equal to or greater than 2, an electrolyte is located in Chamber 1 to Chamber n-m which are connected with each other in series, and a solid fuel is located in Chamber n-m+1 to Chamber n which are connected with each other in series, wherein m is an integer, and 1≤m≤n-1.
The solid fuel package of claim 1, wherein n≤100, or 50, or 20.
The solid fuel package of claim 1, wherein the package further comprisesadditive (s) in any of the chambers.
The solid fuel package of claim 1, wherein Chamber 1 to Chamber n-m is in series with Chamber n-m+1 to Chamber n.
The solid fuel package of claim 1, wherein Chamber 1 to Chamber n-m is in parallel with Chamber n-m+1 to Chamber n.
The solid fuel package of claim 1, wherein there is a mixing compartment after the filter.
The solid fuel package of claim 1, wherein the adjacent two chambers are separated by a separation element.
The solid fuel package of claim 1, wherein the solid fuel is an oxidizable compound chosen from the group consisting of hypophosphorous acid salts, borohydride salt, ammonia borane, formic acid, formate and hydrazine hydrate, and organic chemical hydride.
The solid fuel package of claim 1, wherein the electrolyte is alkali metal hydroxide or alkali metal bicarbonate.
The solid fuel package of claim 1, wherein the molar ratio of the fuel to the electrolyte can be from 50: 1 to 1: 50.
The solid fuel package of claim 1, wherein the filter is a filter paper, filter clothes, a membrane, a sieve, or other types of mesh equipment.
The solid fuel package of claim 1, wherein the solid fuel is NaH ₂PO ₂, and the electrolyte is KOH.
A solid fuel supply system comprising 1) a solvent reservoir containing a solvent, 2) an optional pump, 3) a solid fuel package according to any one of claims 1-9; and 4) a single fuel cell or a fuel cell stack.
The solid fuel supply system of claim 13, wherein the solvent is water.
The solid fuel supply system of claim 13, wherein the single fuel cell comprises a fixing end plate, anode/cathode current collectors, a flow field channel, a gasket, and MEA.