JP7158672B2 - hydrogen generator - Google Patents

Description

Article 30, Paragraph 2 of the Patent Act applies Chunichi Shimbun September 14, 2017 morning edition, page 1, September 14, 2017 ChemElectroChem 2017, 4, 3032-3036 "http://onlinelibrary.wiley.com/ doi/10.1002/celc.201700917/abstract”, issued on October 17, 2017

TECHNICAL FIELD The present invention relates to a hydrogen generator that generates hydrogen by electrolysis.

Conventionally, in Non-Patent Document 1, saccharides such as cellulose and lignin are supplied to a POM (polyoxometalate) solution as an anode catalyst, and light is irradiated to oxidize the saccharides and generate POM molecules. A hydrogen generator is disclosed in which the generated H ^{2 +} is used to generate hydrogen on the cathode side.

Energy & Environmental Science 2016,9,p467-472

However, although the conventional hydrogen generator can use saccharides as a hydrogen source, it uses a POM solution and requires light irradiation, which complicates the structure of the device accordingly.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems, and it is an object of the present invention to provide a hydrogen generator capable of generating hydrogen by electrolysis with a relatively simple configuration.

One aspect of the present invention is an electrolyte (2) having proton conductivity,
an anode (3) provided on one side of the electrolyte;
a cathode (4) provided on the other side of the electrolyte;
a voltage application unit (5) for applying a voltage between the anode and the cathode,
The anode is configured to be supplied with a liquid fuel (LF) containing water, sugars and acids (excluding those containing electrocatalysts and co-catalysts) ,
A hydrogen generator (1) having an operating temperature of 100°C or higher and 250°C or lower.
Another aspect of the present invention is an electrolyte (2) having proton conductivity,
an anode (3) provided on one side of the electrolyte;
a cathode (4) provided on the other side of the electrolyte;
a voltage application unit (5) for applying a voltage between the anode and the cathode,
The anode is configured to be supplied with a liquid fuel (LF) containing water, sugars and acids (excluding those containing electrocatalysts and co-catalysts) ,
The anode and/or the cathode comprise Pt-supported carbon, Pt—Fe alloy-supported carbon, Mo ₂ C, or carbon,
The carbon surface is in the hydrogen generator (1) modified with at least one of carbonyl and carboxyl groups.

In the above hydrogen generator, the saccharide in the liquid fuel supplied to the anode is partly cleaved by the acid and hydrolyzed with water. When a voltage is applied between the anode and the cathode in the voltage application section, H ^{2 +} produced by hydrolysis is drawn out through the proton conductive electrolyte, and hydrogen is generated on the cathode side. According to the above-described hydrogen generator, sugars are used as a hydrogen source, and hydrogen can be generated by electrolysis with a relatively simple configuration without light irradiation.

It should be noted that the symbols in parentheses described in the claims and the means for solving the problems indicate the corresponding relationship with the specific means described in the embodiments described later, and limit the technical scope of the present invention. not a thing

1 is an explanatory view schematically showing the hydrogen generator of Embodiment 1. FIG. FIG. 2 is an explanatory diagram schematically showing a hydrogen generator of Embodiment 2; 4 is a graph showing the relationship between cell voltage and current density in Test 1 of Experimental Example 1. FIG. 4 is a graph showing the relationship between current density and hydrogen production rate in Test 1 of Experimental Example 1. FIG. 4 is a graph showing the relationship between cell voltage and current density in Test 2 of Experimental Example 1. FIG. 4 is a graph showing the relationship between current density and hydrogen production rate in Test 2 of Experimental Example 1. FIG. 3 is a graph showing the relationship between cell voltage and current density in Test 3 of Experimental Example 1. FIG. 3 is a graph showing the relationship between time and hydrogen production rate in Test 3 of Experimental Example 1. FIG. 4 is a photograph showing the state of lignin after sulfuric acid treatment or phosphoric acid treatment in Test 4 of Experimental Example 1. FIG. FT-IR results of lignin before and after phosphoric acid treatment in Test 4 of Experimental Example 1. FIG. 5 is a graph showing the relationship between cell voltage and current density in Test 5 of Experimental Example 1. FIG. FIG. 10 is a diagram showing complex impedance plots of cells A and D in Test 5 of Experimental Example 1; 10 is a graph showing the relationship between time and cell voltage for cells A and D in Test 6 of Experimental Example 1. FIG. 10 is a graph showing the relationship between time and hydrogen sensitivity of Cell A and Cell D in Test 6 of Experimental Example 1. FIG. 7 is a graph showing the relationship between cell voltage and current density in Test 7 of Experimental Example 1. FIG. 7 is a graph showing the relationship between current density and hydrogen production rate in Test 7 of Experimental Example 1. FIG. FIG. 10 is a diagram showing a complex impedance plot of cell A in Test 8 of Experimental Example 1; FIG. 10 is a diagram showing complex impedance plots of cell E, cell F, and cell G in Test 8 of Experimental Example 1; FIG. 10 is a diagram showing the measurement results of the specific surface area in Test 9 of Experimental Example 1; FIG. 10 is a diagram showing XPS measurement results in Test 9 of Experimental Example 1; FIG. 10 is a diagram showing complex impedance plots of cell E, cell H, and cell I in Test 9 of Experimental Example 1; 10 is a graph showing the relationship between time and hydrogen generation rate when voltage is applied to the hydrogen generator in Experimental Example 2. FIG.

(Embodiment 1)
A hydrogen generator of Embodiment 1 will be described with reference to FIG. As illustrated in FIG. 1 , the hydrogen generator 1 of this embodiment has an electrolyte 2 , an anode 3 , a cathode 4 and a voltage applying section 5 . That is, in the hydrogen generator 1 , the cell 10 is composed of the electrolyte 2 , the anode 3 and the cathode 4 . This will be explained in detail below.

The electrolyte 2 has proton conductivity. Specifically, the electrolyte 2 can be configured to contain a proton conductor. More specifically, the electrolyte 2 may be composed of a proton conductor, or may be composed of a proton conductor and an aproton conductor. The aproton conductor can have a role of forming an electrolyte into a membrane by being used together with the proton conductor, for example. Examples of proton conductors include SnP ₂ O ₇ , Sn _1-X In _X P ₂ O ₇ , and proton-conducting solid acids such as phosphoric acid-doped polybenzimidazole. These can be used alone or in combination of two or more. Examples of aproton conductors include fluororesins such as polytetrafluoroethylene (PTFE). These can be used alone or in combination of two or more.

Anode 3 is provided on one side of electrolyte 2 . A cathode 4 is provided on the other side of the electrolyte 2 . Specifically, the anode 3 and the cathode 4 may be joined to the electrolyte 2 or may be in contact with the electrolyte 2 . The former is preferable from the viewpoint of reduction of ohmic resistance.

Both the anode 3 and the cathode 4 can be made of Pt-supported carbon, Pt--Fe alloy-supported carbon, Mo ₂ C, or carbon. When the anode 3 has the above structure, the electrode reaction resistance of the anode 3 during electrolysis can be reduced. On the other hand, when the cathode 4 has the above structure, the electrode reaction resistance of the cathode 4 during electrolysis can be reduced. When both the anode 3 and the cathode 4 have the above structure, the electrode reaction resistance of the anode 3 and the cathode 4 during electrolysis can be reduced, which is advantageous. The combination of the electrode materials for the anode 3 and the cathode 4 is not particularly limited. The combination of the electrode materials for the anode 3 and the cathode 4 may be a combination of the same electrode material or a combination of different electrode materials.

When Pt—Fe alloy-supported carbon is used as the electrode material, the amount of hydrogen generated can be improved compared to the case of using Pt-supported carbon. Here, when carbon is selected as the electrode material, the carbon surface may be modified with at least one of a carbonyl group and a carboxyl group. According to this configuration, it is possible to obtain the hydrogen production device 1 that is relatively inexpensive, has high electrode reaction activity, and is capable of improving the amount of hydrogen produced. The modification of the surface of carbon with carbonyl groups and carboxyl groups can be carried out by oxidation treatment, oxidation-reduction treatment, and the like of carbon. Examples of the oxidation treatment include nitric acid treatment, and examples of the oxidation-reduction treatment include a method of hydrogen reduction after nitric acid treatment.

Here, the hydrogen generator 1 is configured such that the anode 3 is supplied with a liquid fuel LF containing water, sugars, and acid. Hydrogen gas is generated at the cathode 4 .

As the saccharides, specifically, polysaccharides can be mentioned as suitable ones. According to this configuration, it becomes easier to ensure the generation of hydrogen by direct electrolysis of the polysaccharide. Specific examples of polysaccharides include celluloses (including hemicellulose), lignin, and the like. These can be used alone or in combination of two or more. According to this configuration, hydrogen can be generated by directly electrolyzing celluloses and lignin, which have conventionally been considered difficult to extract hydrogen. As celluloses and lignin, for example, those contained in biomass raw materials can be suitably used. Examples of biomass raw materials containing celluloses and lignin include wood, grasses, paper such as newspapers and magazines, and agricultural waste such as rice and rice husks.

Note that when celluloses are used as sugars, H ^{2 +} is produced on the anode 3 side according to (Equation 1). Further, when lignin is used as the sugar, H ⁺ is produced on the anode 3 side according to the following (formula 2). Hydrogen can be generated at the cathode 4 by withdrawing the H ⁺ (protons) thus generated to the cathode 4 side through the electrolyte.
C _6n H _10n+2 O _5n+1 + (7n−1)H ₂ O→6nCO ₂ +24nH ⁺ +24ne ⁻ (Formula 1)
(C ₃₁ H ₃₄ O ₁₁ ) _n +51nH ₂ O→31nCO ₂ +136nH ⁺ +136ne ^- (Formula 2)

Specific examples of acids include phosphoric acid, acetic acid, and sulfuric acid. These can be used alone or in combination of two or more. An excessively strong acid may destroy the saccharide structure itself, while an excessively weak acid may make it difficult to break some of the saccharide bonds. According to the above configuration, it is easy to loosen the saccharides by cutting a part of the bonds of the saccharides, so that it is easy to ensure the generation of hydrogen. Among these acids, phosphoric acid is preferable from the viewpoint of ion conductivity, thermal stability, and the like.

In this embodiment, the hydrogen generator 1 specifically communicates with the liquid fuel supply channel 31 for supplying the liquid fuel LF from the outside and the liquid fuel supply channel 31, as illustrated in FIG. a liquid fuel contact portion 32 that contacts the supplied liquid fuel LF with the anode 3; ,have. 1, the hydrogen generator 1 includes a gas supply channel 41 for supplying a carrier gas (not shown) for recovering the hydrogen produced at the cathode 4, It has a hydrogen generator 42 that communicates with the gas supply channel 41 and causes the generated hydrogen to exist, and a gas discharge channel 43 that communicates with the hydrogen generator 42 and discharges hydrogen. In addition, as carrier gas, inert gas, such as Ar gas and nitrogen gas, etc. can be used, for example.

The voltage applying section 5 can apply a voltage between the anode 3 and the cathode 4 . Specifically, in FIG. 1 , the voltage application unit 5 includes an external power source 51 , a conductor line 52 electrically connecting between the positive electrode and the anode 3 of the external power source 51 , and the negative electrode and the cathode 4 of the external power source 51 . An example is shown having a conductor line 53 electrically connecting between and.

In the hydrogen generator 1, when the saccharides are celluloses, the voltage application unit 5 can be specifically configured to apply a voltage of −1 V or more and 0 V or less. When the voltage is -1 V or higher, deterioration of the electrolyte having proton conductivity can be easily suppressed. When the voltage is 0 V or less, it becomes easier to decompose celluloses.

In the hydrogen generator 1, when the sugar is lignin, the voltage application unit 5 can be specifically configured to apply a voltage of −1 V or more and −0.25 V or less. When the voltage is -1 V or higher, deterioration of the electrolyte having proton conductivity can be easily suppressed. If the voltage is -0.25 V or less, it becomes easier to decompose lignin.

Specifically, the operating temperature of the hydrogen generator 1 can be 100° C. or higher and 250° C. or lower. According to this configuration, it is possible to ensure the generation of hydrogen. The operating temperature is preferably 110° C. or higher, more preferably 120° C. or higher, and even more preferably 150° C. or higher, from the viewpoints of improving the electrode reaction rate, reducing the resistance of the electrolyte 2, and the like. The operating temperature is preferably 240° C. or lower, more preferably 220° C. or lower, and even more preferably 200° C. or lower, from the viewpoint of corrosion resistance of the constituent members.

In the hydrogen generator 1, the saccharides in the liquid fuel LF supplied to the anode 3 are partly cleaved by acid and hydrolyzed with water. When a voltage is applied between the anode 3 and the cathode 4 by the voltage application unit 5, H ^{2 +} produced by hydrolysis is drawn out through the proton conductive electrolyte, and hydrogen is generated on the cathode 4 side. According to the hydrogen generator 1, sugars are used as a hydrogen source, and hydrogen can be generated by electrolysis with a relatively simple configuration without light irradiation.

(Embodiment 2)
A hydrogen generator 1 of Embodiment 2 will be described with reference to FIG. It should be noted that, of the reference numerals used in the second and subsequent embodiments, the same reference numerals as those used in the previously described embodiments represent the same components and the like as those in the previously described embodiments, unless otherwise specified.

As illustrated in FIG. 2, the hydrogen generator 1 of this embodiment includes a cell 10 in which an anode 3, an electrolyte 2, and a cathode 4 are laminated in this order, and a porous anode side contacting the surface of the anode 3. A current collector 63, a porous cathode-side current collector 64 in contact with the surface of the cathode 4, a pair of plate members 73 and 74, and a separator that separates the liquid fuel LF from the generated hydrogen so that they do not mix. 8 and a liquid fuel supply source 9 that continuously delivers liquid fuel LF.

A liquid fuel supply channel 31 , a liquid fuel contact portion 32 , and a liquid fuel discharge channel 33 are formed in one plate member 73 arranged on the anode 3 side. A liquid fuel supply source 9 is connected to the liquid fuel supply channel 31 . In the liquid fuel contact portion 32 , the continuously supplied liquid fuel LF can be brought into contact with the anode 3 through the gaps of the porous anode-side current collector 63 .

On the other hand, the other plate member 74 arranged on the cathode 4 side is connected to the tubular hydrogen generating part 42 in which the generated hydrogen is allowed to exist. Hydrogen generated at the cathode 4 passes through the gaps of the porous cathode-side current collector 64 and fills the hydrogen generation section 42 . The gas supply channel 41 and the gas discharge channel 43 are integrally formed in a tubular shape, and a tubular hydrogen generator 42 is connected between the tubular gas supply channel 41 and the gas discharge channel 43 . ing. As a result, when the carrier gas C flows through the gas supply channel 41 , the hydrogen in the hydrogen generation chamber 42 is discharged from the gas discharge channel 43 together with the carrier gas C. The plate members 73 and 74 can be fastened together by fastening members 740 . The cell 10 is thereby sandwiched between the plate members 73 and 74 .

The separator 8 has an opening 81 with the same shape as the cathode 4 . A cathode 4 is arranged in the opening 81 . The separator 8 can be made of, for example, a fluororesin sheet (tetrafluoroethylene sheet or the like). A sealing member 731 such as a rubber packing is provided between the plate member 73 and the separator 8 to prevent leakage of the liquid fuel LF.

The positive electrode of the external power supply in the voltage application section (not shown in FIG. 2) is electrically connected to the anode-side current collector 63 . The negative electrode of the external power source in the voltage application section is electrically connected to the cathode side current collector 64 . In this embodiment, the anode-side current collector 63 and the cathode-side current collector 64 can be made of, for example, metal mesh members (stainless steel mesh, Au mesh, Pt mesh, etc.).

According to the hydrogen generator 1 of this embodiment, by continuously supplying the liquid fuel LF from the liquid fuel supply source 9 to the anode 3, sugars are continuously directly electrolyzed, and continuously Hydrogen can be produced. The continuously produced hydrogen flows out of the hydrogen producing part 42 and is discharged together with the carrier gas C from the gas discharge channel 43 . Other configurations and effects are the same as those of the first embodiment.

(Experimental example 1)

-Preparation of electrolyte membrane-
An electrolyte membrane was produced by the following method. Specifically, 1.0 g of Sn _0.9 In _0.1 P ₂ O ₇ and 0.04 g of PTFE powder were weighed. Then, they were mixed and adjusted with a rolling mill so as to have a predetermined thickness. Then, it was cut to a size of 16 mm to 20 mm in diameter. An electrolyte membrane was thus prepared.

-Anode preparation-
An anode was produced by the following method. Specifically, a predetermined anode material was hollowed out so as to have a diameter of 12 mm. The hollowed out anode material was then immersed in an 85% aqueous solution of phosphoric acid. In that state, ultrasonic waves were applied continuously for 15 minutes. After that, it was dried at 120° C. for 1 hour. This formed an anode. In Experimental Example 1, a predetermined liquid fuel was placed on the anode in advance. As sugars for the liquid fuel, any one of cellulose, lignin, a mixture of cellulose and lignin derived from cypress wood flour, and a mixture of cellulose and lignin derived from newspaper was used. The liquid fuel used was obtained by mixing 270 mg of an 85% aqueous solution of phosphoric acid with 15 mg of the saccharide.

-Cathode preparation-
A cathode was produced by the following method. Specifically, a predetermined cathode material was hollowed out so as to have a diameter of 8 mm. The hollowed out cathode material was then immersed in an 85% aqueous solution of phosphoric acid. In that state, ultrasonic waves were applied continuously for 15 minutes. After that, it was dried at 120° C. for 1 hour. This formed a cathode.

-Method of making a cell-
A plurality of cells were produced as follows.
A predetermined anode, electrolyte membrane, separator (thickness: 1.5 mm, outer diameter: 16 mm, inner diameter: 8 mm, ring shape) and cathode were sequentially laminated on the surface of SUS316 with a diameter of 16 mm to form a cell. The periphery of the cell was covered with PTFE tape to fix each constituent member. Also, the cell was sandwiched between a pair of Pt meshes. In addition, Ar gas as a carrier gas can be continuously supplied to the cathode at a rate of 100 mLmin ⁻¹ . A specific configuration of each cell used in Experimental Example 1 is shown below.

<Cell A>
・Electrolyte membrane: mixture of _{Sn0.9In0.1P2O7} and _{PTFE ,} film thickness ₂₅₀ µm
Anode: Pt-supporting carbon (hereinafter sometimes referred to as Pt/C)
・Cathode: Pt-supported carbon (Pt/C)
The amount of Pt supported is 2.0 mg/cm ² . The same applies hereinafter.
Hereinafter, the cell A may be expressed as Pt/C||Pt/C. Here, || means an electrolyte membrane, the left side of || means an anode, and the right side of || means a cathode.

<Cell B>
・Electrolyte membrane: mixture of _{Sn0.9In0.1P2O7} and _{PTFE ,} film thickness ₂₅₀ µm
- Anode: _Mo2C
・Cathode: Pt-supported carbon (Pt/C)
Hereinafter, the cell B may be expressed as Mo ₂ C||Pt/C.

<Cell C>
・Electrolyte membrane: mixture of _{Sn0.9In0.1P2O7} and _{PTFE ,} film thickness ₂₅₀ µm
- Anode: _Mo2C
- Cathode: _Mo2C
Hereinafter, the cell C may be expressed as Mo ₂ C||Mo ₂ C.

<Cell D>
・Electrolyte membrane: mixture of _{Sn0.9In0.1P2O7} and _{PTFE ,} film thickness ₂₅₀ µm
Anode: Pt-Fe alloy supported carbon (hereinafter sometimes referred to as Pt-Fe/C)
・Cathode: Pt-supported carbon (Pt/C)
The amount of Pt--Fe supported is 2.0 mg/cm ² .
Hereinafter, the cell D may be expressed as Pt--Fe/C||Pt/C.

<Cell E>
・Electrolyte membrane: mixture of _{Sn0.9In0.1P2O7} and _{PTFE ,} film thickness ₂₅₀ µm
・Anode: Carbon (Ketjen Black) (hereinafter sometimes referred to as C, KB)
・Cathode: Pt-supported carbon (Pt/C)
Hereinafter, the cell E may be expressed as C, KB||Pt/C.

<Cell F>
・Electrolyte membrane: mixture of _{Sn0.9In0.1P2O7} and _{PTFE ,} film thickness ₂₅₀ µm
・Anode: Carbon (Vulcan) (hereinafter sometimes referred to as C or V)
・Cathode: Pt-supported carbon (Pt/C)
Hereinafter, the cell F may be expressed as C, V||Pt/C.

<Cell G>
・Electrolyte membrane: mixture of _{Sn0.9In0.1P2O7} and _{PTFE ,} film thickness ₂₅₀ µm
・Anode: Carbon (acetylene black) (hereinafter sometimes referred to as C, AB)
・Cathode: Pt-supported carbon (Pt/C)
Hereinafter, the cell G may be expressed as C, AB||Pt/C.

<Cell H>
・Electrolyte membrane: mixture of _{Sn0.9In0.1P2O7} and _{PTFE ,} film thickness ₂₅₀ µm
・Anode: carbon surface-modified with carbonyl and carboxyl groups (oxidized ketjen black)
・Cathode: Pt-supported carbon (Pt/C)
The oxidized Ketjenblack is KB1 in Test 9 described later.
Hereinafter, cell H may be expressed as C, KB1||Pt/C.

<Cell I>
・Electrolyte membrane: mixture of _{Sn0.9In0.1P2O7} and _{PTFE ,} film thickness ₂₅₀ µm
・Anode: Carbon surface-modified with carbonyl group and carboxyl group (Ketjen black with redox treatment)
・Cathode: Pt-supported carbon (Pt/C)
The ketjen black subjected to the oxidation-reduction treatment is KB2 in Test 9 described later.
Hereinafter, the cell I may be expressed as C, KB2||Pt/C.

－Various measurement methods－
Using each cell, the current-voltage curve, impedance characteristics, and voltage change at constant current were evaluated when a predetermined liquid fuel was supplied at a predetermined operating temperature. For the measurement, an electrochemical interface ("SI1287" manufactured by Solartron) and a frequency response analyzer ("SI1260" manufactured by Solartron) were used.

<Measurement of current-voltage curve>
Current-voltage curves were measured using a potentiostat by scanning in the range of current densities from 0 to 0.5 Acm ⁻² every 20 mVsec ⁻¹ . In addition, the current density was standardized by the area of the cathode.

<Impedance characteristics>
Impedance spectra were recorded in the frequency range of 0.1-10 ⁶ Hz and bias voltage in the range of 0-0.4V.

<Constant current test (batch type)>
Using galvanostatic, a constant current in the range of 0.05 to 0.2 Acm ⁻² was applied and the voltage was measured up to 3.0V.

<Measurement of hydrogen production>
The amount of hydrogen obtained from the cathode during evaluation of the constant current test was measured using a mass spectrometer (manufactured by Pfeiffer Vacuum, "ThermoStar"). Note that while measuring the amount of hydrogen with the mass spectrometer, a galvanostatic system was used to pass a constant current in the range of 0 to 0.2 Acm ⁻² .

Specific test contents and test results are shown below.
-Test 1-
Using cell A (Pt/C||Pt/C), a liquid fuel composed of cellulose, water, and phosphoric acid was supplied to the anode, and a voltage was applied between the anode and cathode at a given operating temperature. . At this time, the operating temperatures were 100°C, 125°C, 150°C, 175°C and 200°C. For comparison (blank), a liquid fuel containing no cellulose and composed of water and phosphoric acid was supplied to the anode, and a voltage was applied in the same manner as above. Then, the hydrogen generation rate at the cathode was determined.

FIG. 3 shows the relationship between cell voltage and current density when cellulose is used as the sugar and the operating temperature is varied. According to FIG. 3, when a voltage is applied in the negative direction (positive value in the graph), a liquid fuel composed of cellulose, water, and phosphoric acid is supplied to the anode at any operating temperature. It can be seen that a current is generated when

Next, in order to examine whether or not the current is used for hydrogen generation, we used cellulose as the sugar and determined the relationship between the current density and the hydrogen generation rate when the operating temperature was changed. The results are shown in FIG. According to FIG. 4, it can be seen that the amount of hydrogen produced increases linearly as the current density increases. In FIG. 4, the dotted line indicates the theoretical amount of hydrogen produced if all the current is used for hydrogen production. According to FIG. 4, the amount of hydrogen produced at each current density is almost the same as the theoretical amount of production, so it can be seen that hydrogen production by electrolysis of saccharides has been achieved.

-Test 2-
Using cell A (Pt/C||Pt/C), a liquid fuel composed of lignin, water, and phosphoric acid was supplied to the anode, and a voltage was applied between the anode and cathode at a given operating temperature. . At this time, the operating temperatures were 100°C, 125°C, 150°C, 175°C and 200°C. For comparison (blank), a liquid fuel containing no lignin but composed of water and phosphoric acid was supplied to the anode, and a voltage was applied in the same manner as above. Then, the hydrogen generation rate at the cathode was determined.

FIG. 5 shows the relationship between cell voltage and current density when lignin is used as the sugar and the operating temperature is varied. According to FIG. 5, when voltage is applied in the negative direction (positive value in the graph), liquid fuel composed of lignin, water, and phosphoric acid is supplied to the anode at any operating temperature. It can be seen that a current is generated when However, it can be seen that the current is generated when the applied voltage is -0.25 V or less. When cellulose was used as the saccharide, as shown in FIG. 3, the current was generated when the applied voltage was 0 V or less, confirming that lignin is more difficult to electrolyze than cellulose.

Further, FIG. 6 shows the relationship between the current density and the hydrogen production rate when lignin is used as the saccharide and the electrode configuration is changed. Here, in addition to the cell A (Pt/C||Pt/C), by using the cell B (Mo ₂ C||Pt/C) and the cell C (Mo ₂ C||Mo ₂ C) , varied the electrode configuration. According to FIG. 6, the amount of hydrogen generated at each current density almost matches the theoretical amount, regardless of whether the Pt/C electrode or the Mo ₂ C electrode is used, and hydrogen generation by electrolysis of sugars is realized. I know it's done.

-Test 3-
Using cell A (Pt/C||Pt/C), a liquid fuel composed of predetermined sugars, water, and phosphoric acid was supplied to the anode, and a voltage was applied between the anode and cathode at an operating temperature of 175°C. applied. At this time, cellulose, lignin, or a mixture of cellulose and lignin derived from cypress wood flour was used as the sugar. For comparison (blank), a liquid fuel containing no saccharide but composed of water and phosphoric acid was supplied to the anode, and a voltage was applied in the same manner as described above.

FIG. 7 shows the relationship between the cell voltage and the current density when cellulose, lignin, or a mixture of cellulose and lignin derived from hinoki wood flour is used as sugars. According to FIG. 7, the curve when using cypress wood powder when applying voltage in the negative direction (positive value in the graph) is a combination of the curve when using cellulose and the curve when using lignin. It can be seen that they match well. From this result, it was confirmed that hydrogen generation by electrolysis can be realized even when sugars are mixed.

In addition, when cell C (Mo ₂ C||Mo ₂ C) was used instead of cell A (Pt/C||Pt/C) and cypress wood flour was used, the amount of current was increased at an operating temperature of 175°C. While changing, the amount of hydrogen produced was measured at fixed time intervals. The amount of current was 20 mAcm ^-2 , 40 mAcm ^-2 and 60 mAcm ^-2 . The results are shown in FIG. According to FIG. 8, it was confirmed that hydrogen could be generated stably according to the amount of current.

-Test 4-
At room temperature, lignin was sulfated (H ₂ SO ₄ treated) or phosphoric acid treated (H ₃ PO ₄ treated). FIG. 9(a) shows the state of lignin treated with sulfuric acid at room temperature. FIG. 9(b) shows the state of lignin treated with phosphoric acid at room temperature. Moreover, the lignin after the sulfuric acid treatment and the lignin after the phosphoric acid treatment were held at 200° C. for 30 minutes. FIG. 9(c) shows the state of lignin treated with sulfuric acid after being kept at 200°C. FIG. 9(d) shows the state of the phosphoric acid-treated lignin after being kept at 200°C. Incidentally, FIGS. 9A to 9D are observation results by a scanning electron microscope. According to FIG. 9, when phosphoric acid is used as the acid, even if the operating temperature is high, the structure of the saccharide itself is less likely to be broken, and a portion of the saccharide bond is moderately reduced compared to the case where sulfuric acid is used as the acid. can be cut off.

In addition, in order to average the lignin before and after the phosphoric acid treatment at 200 ° C., each sample was crushed in a mortar, transferred to a diamond plate, thinned with a needle, and then subjected to FT-IR measurement. FIG. 10 shows the results of FT-IR of lignin before and after phosphoric acid treatment. According to FIG. 10, it can be seen that the peak after phosphoric acid treatment is broader than the peak before phosphoric acid treatment. From this result, it was confirmed that the combined use with phosphoric acid can weaken the molecular bonding force of lignin.

-Test 5-
Using cell A (Pt/C||Pt/C) or cell D (Pt—Fe/C||Pt/C), supplying a liquid fuel composed of lignin, water, and phosphoric acid to the anode, A voltage was applied between the anode and cathode at a given operating temperature. At this time, the operating temperatures were 100°C, 125°C, and 150°C.

FIG. 11 shows the relationship between cell voltage and current density when lignin is used as the sugar and the electrode configuration and operating temperature are varied. According to FIG. 11, it can be seen that the cell D having the Pt—Fe/C electrode can increase the current density, that is, the amount of hydrogen generated can be increased compared to the cell A having the Pt/C electrode. . FIG. 12 shows complex impedance plots of cell A (Pt/C||Pt/C) and cell D (Pt—Fe/C||Pt/C). According to FIG. 12, it was confirmed that the Pt--Fe/C electrode can reduce the electrode reaction resistance compared to the Pt/C electrode.

-Test 6-
Using cell A (Pt/C||Pt/C) or cell D (Pt—Fe/C||Pt/C), supplying a liquid fuel composed of lignin, water, and phosphoric acid to the anode, Changes in cell voltage were measured at an operating temperature of 150° C. and a constant current. The results are shown in FIG. According to FIG. 13, it was confirmed that in any cell in this example, although the cell voltage gradually increased due to depletion of lignin in the liquid fuel, a substantially stable cell voltage was obtained.

Also, FIG. 14 shows the hydrogen sensitivity measured by the mass spectrometer. In addition, in FIG. 14, M/Z=2 means that the molecular weight is 2, that is, hydrogen. According to FIG. 14, it was confirmed that hydrogen was stably generated during current application in any of the cells.

-Test 7-
Using cell A (Pt/C||Pt/C), a liquid fuel composed of predetermined sugars, water, and phosphoric acid was supplied to the anode, and a voltage was applied between the anode and cathode at an operating temperature of 175°C. applied. At this time, cellulose, lignin, or a mixture of newspaper-derived cellulose and lignin was used as the sugar. Then, the hydrogen generation rate at the cathode was determined.

FIG. 15 shows the relationship between cell voltage and current density when cellulose, lignin, or a mixture of newspaper-derived cellulose and lignin is used as sugars. According to FIG. 15, when a voltage is applied in the negative direction (positive value in the graph), a current is generated when a liquid fuel composed of sugars, water, and phosphoric acid is supplied to the anode. I understand.

In addition, in order to examine whether the current is used for hydrogen generation, FIG. 16 shows the relationship between the current density and the hydrogen generation rate when using a mixture of newspaper-derived cellulose and lignin as sugars. According to FIG. 16, it can be seen that the amount of hydrogen produced increases linearly as the current density increases. In FIG. 16, the dotted line indicates the theoretical amount of hydrogen produced if all the current is used for hydrogen production. According to FIG. 16, since the amount of hydrogen produced at each current density is almost the same as the theoretical amount of production, it can be seen that hydrogen production by electrolysis of saccharides has been achieved.

-Test 8-
Using cell A (Pt/C||Pt/C), a liquid fuel consisting of a mixture of cellulose and lignin derived from newspaper, water, and phosphoric acid is supplied to the anode, and at a given operating temperature, the anode and A voltage was applied across the cathodes. At this time, the operating temperatures were 100°C, 125°C, 150°C and 175°C. FIG. 17 shows a complex impedance plot at this time. Further, in FIG. 18, instead of cell A (Pt/C||Pt/C), cell E (C, KB||Pt/C), cell F (C, V||Pt/C), cell G (C, AB||Pt/C) is used to show complex impedance plots when similar electrolysis is performed at an operating temperature of 175°C.

From the peak at the operating temperature of 175° C. in FIG. 17 and FIG. 18, it can be seen that the resistance value is lower and the electrolysis is easier when the carbon electrode is used. In other words, it can be seen that the hydrogen generator can function even when the C electrode is used without using the P/C electrode. Further, from FIG. 18, the resistance values are in the order of cell E (C, KB||Pt/C)<cell F (C, V||Pt/C)<cell G (C, AB||Pt/C). It was big. The specific surface area of carbon increases in the order of acetylene black (76 m ² g ⁻¹ ) < Vulcan (214 m ² g ⁻¹ ) < Ketjen black (1216 m ² g ⁻¹ ). It can be seen that the capacitance and active sites increase and are reflected in the resistance value. From this result, it can be said that the preferred carbon species is Ketjenblack, which has a large specific surface area of 1000 m ² g ⁻¹ or more compared to others.

-Test 9-
In order to investigate the effect of functional groups on the carbon surface, the following test was performed using Ketjenblack as the carbon. Specifically, Ketjenblack subjected to oxidation treatment (hereinafter referred to as sample KB1), Ketjenblack subjected to reduction treatment after oxidation treatment (hereinafter referred to as sample KB2), and untreated Ketjenblack without these treatments A black (hereinafter referred to as sample KB0) was prepared. The oxidation treatment was carried out by adding 1.0 g of Ketjenblack to an aqueous solution obtained by mixing 20 mL of 24% nitric acid and 30 mL of water, and stirring the mixture on a hot plate at room temperature and 300 rpm for 72 hours. The reduction treatment was performed by heat-treating the Ketjenblack after the oxidation treatment at 600° C. in a hydrogen atmosphere. Next, specific surface area measurement (BET specific surface area, adsorbed substance: N ₂ ) and XPS measurement were performed on the prepared samples KB0, KB1, and KB2. In the XPS measurement, changes in amounts of COO groups, C═O groups, and COH groups were comparatively measured by waveform separation. FIG. 19 shows the measurement results of the specific surface area. FIG. 20 shows the XPS measurement results.

According to FIG. 19, no significant change was observed in the specific surface area due to the difference between the oxidation treatment and the oxidation-reduction treatment. However, according to FIG. 20, it can be seen that the peaks of the carbonyl group and the carboxyl group are stronger when the oxidation treatment and the oxidation-reduction treatment are performed. In particular, it can be seen that the peak of the carboxyl group is enhanced when the oxidation treatment is performed, and the peak of the carbonyl group is enhanced when the oxidation-reduction treatment is performed. When the ratio of carbonyl groups is higher than the ratio of carboxyl groups, for example, heat treatment at a high temperature of about 600° C. may be performed so that the carboxyl groups are eliminated, leaving the carbonyl groups.

Cell E (C, KB||Pt/C), Cell H (C, KB1||Pt/C), and Cell I (C, KB2||Pt/C) were used to produce cellulose and lignin derived from newspaper. A liquid fuel consisting of a mixture, water and phosphoric acid was fed to the anode and a voltage was applied between the anode and cathode at an operating temperature of 175°C. FIG. 21 shows a complex impedance plot at this time.

According to FIG. 21, the resistance value was the lowest when the Ketjenblack (KB2) electrode subjected to oxidation-reduction treatment was used. In addition, since the specific surface area does not change, it does not affect the decrease in the resistance value this time. It is believed that this is because the number of carbonyl groups and carboxyl groups on the carbon surface increased, which increased the density of active sites and facilitated the progress of the electrode reaction. From this result, it was confirmed that modifying the carbon surface with at least one of a carbonyl group and a carboxyl group is effective for the electrolysis of saccharides.

(Experimental example 2)
A hydrogen generator according to the configuration shown in Embodiment 2 was prepared. Specifically, the cell configuration in the hydrogen generator is as follows, and was basically produced in the same manner as Cell I of Experimental Example 1.
・Electrolyte membrane: mixture of _{Sn0.9In0.1P2O7} and _{PTFE ,} film thickness ₂₅₀ µm
・Anode: carbon surface-modified with carbonyl group and carboxyl group (Ketjen black subjected to oxidation-reduction treatment as described above)
・Cathode: Pt-supported carbon (Pt/C)
However, the anode was produced as follows. 0.1 g of Ketjenblack and 0.85g of 85% aqueous solution of phosphoric acid were mixed to form a slurry, and then 10 mgcm ⁻² of Ketjenblack subjected to the oxidation-reduction treatment described above was applied to carbon paper. Then, the carbon paper was hollowed out with a size of 12 mm in diameter. This formed the anode.

Further, to the anode of the cell, a liquid fuel composed of a mixture of cellulose and lignin derived from newspaper, water, and phosphoric acid can be continuously supplied from a syringe pump as a liquid fuel supply source. At this time, the liquid fuel was continuously supplied at a rate of 0.07 to 0.44 mLmin ⁻¹ . Ar gas as a carrier gas was continuously flowed to the cathode side at a rate of 100 mLmin ⁻¹ . A stainless steel mesh was used for the anode-side current collector, and an Au mesh was used for the cathode-side current collector. PTFE was used for the separator. The operating temperature was 175°C. In the constant current test in this experimental example, the galvanostatic applied a constant current in the range of 0 to 0.2 Acm ⁻² .

FIG. 22 shows the relationship between time and hydrogen generation rate when a voltage is applied to the hydrogen generator. According to FIG. 22, it can be seen that although there is noise, stable and continuous hydrogen generation can be achieved in accordance with the amount of current. Note that the hydrogen production rate was a value equivalent to the theoretical value.

In addition, the energy consumed in the electrolysis of sugars using the surface-modified carbon electrode is approximately 0.6 kWh (Nm ³ ) ⁻¹ , which is 2.0 kWh (Nm 3 ) −1 of the energy consumed in the electrolysis of ethanol. Nm ³ ) ⁻¹ . Therefore, it can be said that the energy required for hydrogen generation can be significantly reduced according to the above hydrogen generator. In addition, the energy consumed in the electrolysis of sugars using a Pt/C electrode is approximately 0.8 kWh (Nm ³ ) ⁻¹ , so compared with this, the surface-modified carbon electrode is used. can be said to be superior.

The present invention is not limited to the above-described embodiments and experimental examples, and various modifications can be made without departing from the scope of the invention. Moreover, each configuration shown in each embodiment and each experimental example can be combined arbitrarily.

REFERENCE SIGNS LIST 1 hydrogen generator 2 electrolyte 3 anode 4 cathode 5 voltage application unit 6 liquid fuel

Claims (11)

an electrolyte (2) having proton conductivity;
an anode (3) provided on one side of the electrolyte;
a cathode (4) provided on the other side of the electrolyte;
a voltage application unit (5) for applying a voltage between the anode and the cathode,
The anode is configured to be supplied with a liquid fuel (LF) containing water, sugars, and acid (excluding those containing electrocatalysts and co-catalysts) ,
A hydrogen generator (1) having an operating temperature of 100°C or higher and 250°C or lower. The hydrogen generator according to claim 1, wherein the anode comprises Pt-supported carbon, Pt--Fe alloy-supported carbon, Mo ₂ C, or carbon. 3. The hydrogen generator according to claim 1, wherein the cathode comprises Pt-supported carbon, Pt--Fe alloy-supported carbon, Mo ₂ C, or carbon. 4. The hydrogen generator according to claim 2 or 3, wherein the carbon surface is modified with at least one of a carbonyl group and a carboxyl group. an electrolyte (2) having proton conductivity;
an anode (3) provided on one side of the electrolyte;
a cathode (4) provided on the other side of the electrolyte;
a voltage application unit (5) for applying a voltage between the anode and the cathode,
The anode is configured to be supplied with a liquid fuel (LF) containing water, sugars, and acid (excluding those containing electrocatalysts and co-catalysts) ,
The anode and/or the cathode comprise Pt-supported carbon, Pt—Fe alloy-supported carbon, Mo ₂ C, or carbon,
A hydrogen generator (1), wherein the carbon surface is modified with at least one of a carbonyl group and a carboxyl group. The hydrogen generator according to claim 5, wherein the operating temperature is 100°C or higher and 250°C or lower. The hydrogen generator according to any one of claims 1 to 6, wherein the acid is at least one selected from the group consisting of phosphoric acid, acetic acid, and sulfuric acid. The hydrogen generator according to any one of claims 1 to 7, wherein the saccharide is a polysaccharide. The hydrogen generator according to any one of claims 1 to 8, wherein the saccharides are at least one of celluloses and lignin. The saccharides are celluloses,
The hydrogen generator according to any one of claims 1 to 9, wherein the voltage application section is configured to apply a voltage of -1 V or more and 0 V or less. The sugar is lignin,
10. The hydrogen generator according to any one of claims 1 to 9, wherein the voltage application unit is configured to apply a voltage of -1 V or more and -0.25 V or less.

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