WO2008009742A1

WO2008009742A1 - Anodic catalysts consisting of noble metals spontaneously deposited onto nanostructured catalysts composed of transition metals, their synthesis and use in fuel cells

Info

Publication number: WO2008009742A1
Application number: PCT/EP2007/057518
Authority: WO
Inventors: Paolo Bert; Claudio Bianchini; Chiara Emiliani; Giuliano Giambastiani; Serena Santiccioli; Alessandro Tampucci; Francesco Vizza
Original assignee: Acta S.P.A.
Priority date: 2006-07-20
Filing date: 2007-07-20
Publication date: 2008-01-24
Also published as: ITFI20060180A1

Abstract

Here within are described anodic catalysts obtained by the spontaneous deposition of noble metals, preferably palladium or platinum, onto existing nanostructured catalysts based upon transition metals. The method for their preparation is reported along with their use in fuel cells.

Description

ANODIC CATALYSTS CONSISTING OF NOBLE METALS SPONTANEOUSLY DEPOSITED ONTO NANOSTRUCTURED CATALYSTS COMPOSED OF TRANSITION METALS, THEIR SYNTHESIS AND USE IN FUEL CELLS. Field of the invention The present invention refers to the field of catalysts for anode electrodes of fuel cells with electrolytes comprised of polymeric ionic exchange membranes. State of the art

A fuel cell is a device capable of transforming directly the chemical energy contained in a fuel into electrical energy. The process for the production of electrical energy in a fuel cell is silent without moving parts and produces heat, water and in some cases CO₂ depending upon the type of fuel used that contains gaseous hydrogen or a compound containing atomic hydrogen. Whatever the fuel all fuel cells use as co-reagent oxygen pure or atmospheric that is transformed into water. A modern polymeric electrolyte pure hydrogen powered fuel cell is comprised of two electrodes made of porous and conductive material separated by a polymeric membrane permeable to ions called the electrolyte.

Fuel cells fed with hydrogen that contain a solid electrolyte consisting of a polymeric membrane are known as PEMFC or Polymer Electrolyte Membrane Fuel Cell, while fuel cells that run on aqueous solutions of compounds containing bound hydrogen, generally alcohols, are known as DFC or Direct Fuel Cell. The most common type of DFC uses methanol (CH₃OH) and is known as a Direct Methanol Fuel Cell (DMFC). A typical state of the art DMFC is constructed and functions very similar to a PEMFC. In addition the electrolyte is also made up of a polymeric membrane either cation exchange or anion exchange, and both anodic and cathodic catalysts are based upon platinum and platinum alloys. When an anion exchange polymeric electrolyte is used, the hydroxide ions produced at the cathode, pass through the membrane to anode thus closing the circuit. In fuel cells both anodic and cathodic reactions occur using catalysts (electrocatalysts), generally containing metal particles highly dispersed and of small dimensions, generally from 2 to 50 nm (10^"9 m) supported on porous and conductive materials such as Vulcan or Ketjen black. The development of fuel cells of the type PEMFC, DMFC e DFC, like all fuel cells which utilise platinum is dramatically limited by the low natural abundance of this metal and hence its high cost (the natural reserves of platinum are only 5000 tonnes, Johnson Matthey in Platinum Metals Rev. 2004, 48, 34). A second limitation in the use of platinum based catalysts in PEMFC but most importantly in direct alcohol fuel cells (DAFC) is the fact that platinum based cathodes are sensitive to fuel crossover which causes significant cathode polarisation. In addition platinum based anodes are easily deactivated by very small quantities of carbon monoxide (CO) that is an intermediate in the oxidation of alcohols and is also contained in hydrogen gas obtained by reforming.

In addition platinum oxidatively decomposes water at high potentials (between 0.6 and 0.8 V vs. RHE) limiting the capacity to oxidise absorbed CO) causing large anodic over potentials. There are also problems linked to the type of alcohol used. For example no state of the art platinum based catalyst also in combination with other metals form electrocatalysts for fuel cell anodes in DEFC s are capable of oxidising fully ethanol to CO₂, and hence utilising all the available specific energy W_θ (8 KWh/Kg), at temperatures in which available polymeric cationic or anionic exchange membranes are stable (< 100 °C). The same can be said for ethylene glycol. In addition, platinum based anodic catalysts are prone in the presence of ethanol to an irreversible process of deactivation due to the formation of thin oxide layer on the surface. No state of the art anodic catalyst based upon binary or ternary alloys of platinum- other(i) metal(l), even at high metal loading has demonstrated the capacity to produce reasonable power (mW/cm²) in a self breathing DEFC. In a system using an anode based on Pt/Sn (2 mg/cm²) and a cathode containing Pt (4 mg/cm²), at temperatures above 90 °C, using an oxygen pressure of 3 bar have been reported power densities of a few tens of mW/cm² (C. Lamy et al. J. Power Sources 2002, 105, 283-296; C. Lamy et al. J. Appl. Electrochem. 2001 , 31 , 799-809). Also in this case the oxidation of ethanol at the anode was only partial without complete production of CO₂. Similar results have been reported using ethylene glycol as the fuel (C. Lamy et al. J. Appl. Electrochem. 2001 , 31 , 799-809; W. Hauffe and J.Hetbaum Electrochimica Acta 1978, 23, 299).

There exists a number of synthetic methods for the production of electrocatalysts based upon only platinum and platinum alloys with other metals. One of the most common methods involves the deposition of a platinum salt onto a conductive support, generally carbon for example Vulcan XC-72, followed by reduction of the metal in an aqueous suspension with an appropriate reducing agent or in gas phase with hydrogen.

An analogous method involves the addition of a second metal salt. Often the resulting material is retreated under reducing conditions or under an inert gas. An example of this type of process is described in patent US 6,379,834 B1 , Apr. 30, 2003, for a series of Pt/Mo based electrocatalysts.

Electrochemical methods for the preparation of fuel cell anodic and cathodic electrocatalysts involve the electrodeposition of one metal at a time, usually platinum followed by other metals. Electrochemical preparative methods for anodic and cathodic electrocatalysts for fuel cells based upon alloys of platinum with other metals are described in the following patents: Pt/Ru/Pd in US 6,498,121 B1 (Dec. 24, 2002); Pt/Ru/Ni in US 6,517,965 B1 (Feb. 1 1 , 2003); Pt-Ru-Pd in US 6,682,837 B2 (Jan. 27, 2004); Pt/Ru/Ni in US 6,723,678 B2 (Apr. 20, 2004). In light of the above problems, great efforts have lead to the realisation of non platinum catalysts for DFC and PEMFC. Palladium, for example has aroused interest because it is 50 times more abundant in nature than platinum and is capable of promoting the electrochemical oxidation of methanol in acidic media when dispersed on nanotubes of TiO₂ (H. L. Li et al., J. Solid State Chem., 2005, 178, 1996). It has been observed that in alkaline media catalysts based upon palladium supported on Ce, Ni, Co and Mn oxides act as electrocatalysts for the oxidation of alcohols like methanol, ethanol, ethylene glycol and glycerol ( P. K. Shen et al., Electrochem. Commun., 2006, 8, 184-188). Such electrocatalysts are superior to platinum catalysts on carbon supports in terms of activity and tolerance to the presence of carbon monoxide. The use in PEMFC and DAFC type fuel cells of electrocatalysts comprised of metals from the first transition series, in particular Fe, Co and Ni, is currently having notable development. Highly efficient electrocatalysts used to make DEFC fuelled by methanol and higher alcohols have been described in the patent application "Platinum-free electrocatalysts materials (WO 2004/036674) and "Catalysts for fuel cells electrodes based on platinum and its alloys, their preparation and use and fuel cell containing them" (WO 2006/005724 A2).

These catalysts from now on known as nanostructured catalysts, also known by the commercial trademark HYPERMEC^®, are composed of nanostructured particles (generally 1 -10 nm), formed of transition metal alloys based mostly on non noble metals like Fe, Co and Ni, but also on other metals like Pt ,Pd, Ru, Mo, Sn, La, V, Mn, Ir, Rh. These nanostructured catalysts are obtained using templating resins formed from the condensation of a 1 ,3-diol containing a coordinating nitrogen, with a 3,5-disubstituted phenol and formaldehyde or paraformaldehyde. These resins are capable of coordinating metal salts to give adducts that one reduced with hydrogen gas or other reducing agents produce catalytic materials for anodic and cathodic electrodes in fuel cells of the type PEMFC, AFC, DFC, DMFC, DEFC and in general DAFC.

In fuel cells which contain anionic exchange polymeric membranes, alcohols like methanol, ethanol, and ethylene glycol are oxidised completely to CO₂ at room temperature at anodes made with the anodic nanostructured catalysts whereas they are inactive on nanostructured cathodes hence eliminating the problem of cathodic overpotentials caused by alcohol crossover.

For these reasons, the metal loading in the nanostructured catalysts in DAFC type cells is generally much less, between 0.10 and 2 mg/cm², compared to traditional platinum based catalysts (5-10 mg/cm²) and higher concentrations of alcohol can be used (up to 25 wt%).

Due to the nature of the metals used in the anodic nanostructured catalysts which are generally non noble, if used in DAFC type cells a basic environment is required, that is the use of an anionic exchange polymeric membrane to eliminate any possible corrosion.

In DAFC type cell with an appropriate an anionic exchange polymeric electrolyte fuelled with an aqueous solution of methanol, (bio)ethanol or ethylene glycol and at atmospheric pressure, the nanostructured catalysts are capable of producing high power densities, up to 65 mW/cm² at voltages between 200 and 600 mV at room temperature, for long periods with an efficiency between 25 and 35%. The loss in efficiency, due to passivation of the anodic catalyst or presence of polarization caused by mass transport effects or the formation of thick hydroxide layers, is generally low (10-20% after 100-500 hours depending on the power produced).

This effect is more or less common to other state of the art catalysts also for noble metal based catalysts. The electro-oxidation of alcohols is invariably characterised by a reduction in the current density at constant potential and temperature (H. Angerstein-Kozlowska et al. J. Electrochem. Soc. 1973, 120, 756). In the case of the formation of surface oxides, the catalytic activity is commonly regenerated by the application of potential cycling around the value of surface oxide formation. There exist synthetic methods for the preparation of anodic catalysts by the spontaneous deposition of platinum onto ruthenium particles dispersed on a carbon support.

One of these methods uses the suspension of ruthenium/Vulcan XC-72R materials in an aqueous solution of a platinum(IV) or platinum(ll) salt which is then stirred for a few minutes before washing and drying the resulting product. The resulting electrocatalysts have a platinum content lower than commercial Pt/Ru catalysts and demonstrate a higher activity in both the electrooxidation of methanol and ethanol as well as the oxidation of H₂ with a high CO content (J. X. Yang et al., J. of Electrochem Soc, 2003, 150, A1 108-A1 1 17; E. V. Spinace et al., J. Power Sources, 2004, 129, 121 ). The mechanism of the spontaneous deposition is not yet clear. The deposition of a noble metal like platinum on ruthenium can be likened to the oxidative dissolution of ruthenium(O) to ruthenium (II), but is probably more like the interaction of platinum species with RuOH formed on the surface of the catalyst as shown in equation 1 : Ru⁰ + X(H₂O) → RuO_xH_x + 2(x - y)H⁺ + (2x-y)e^" eq. 1

[PtCI₆]^2" + 4 e^" → Pt⁰ + 6Cl^" The spontaneous deposition of RuCI₃ in a solution of HCIO₄ on sheets of Pt(11 1 ), Pt(I OOO) and Pt(H O) has also been described which leads to the formation of islands of ruthenium on platinum (A. Wieckowski et al., Surface Science Letters 2002, 506, L268-L274).

Noble metals like Pt, Pd and Ag can also be deposited spontaneously on Au(1 11 ) using a synthetic technique that utilises the removal of a Cu template layer originally deposited on Au(III). Noble metal salts can be deposited from solution onto Cu-Au layers by a spontaneous irreversible redox reaction in which a layer of copper is oxidised passing into solution as Cu(II), while metals like Pt, Pd or Ag are reduced and deposited onto Au (S. R. Brankovic, et al., Surface Science Letters 2001 , 474, L173-L179; R. R. Adzic et al., Electrochimica. Acta 2003, 48, 3841 -3849).

It has also been observed the formation of Pt-Ni alloys by the spontaneous deposition of an aqueous solution of H₂PtCI₆ under acidic conditions onto nickel discs (T. Nakashima et al., Abs 50, 206th Meeting, 2004 The Electrochemical Soc. Inc.).

The redox reaction that occurs according to equation 2 results in an electrode modified with nickel that is active in the catalytic electro-oxidation of methanol Pt(II) + Ni(O) → Pt(O) + Ni(II) eq. 2

In light of the state of the art, the preparation of more efficient and more stable catalysts for use in DFC fuel cell electrodes is an objective of fundamental importance.

Summary of the invention

This invention enables the improvement in the stability and performance of nanostructured catalysts based upon transition metals preferably Ni, Co and Fe using a synthetic method involving the spontaneous deposition of one or more noble metals like palladium, platinum, ruthenium, gold to name a few, onto preformed nanostructured catalysts, that also function as a support for the noble metal. Brief description of the figures Figure 1 - Simplified scheme of a typical PEMC type fuel cell. Figure 2 - Simplified scheme of a typical DFC type fuel cell. Figure 3 - Polarisation curves of two direct ethanol fuel cells (DEFC) a and b for the cell described in example of cell n°. 1.

Figure 4 - Durability test at constant power for the DEFC cells a and b with the characteristics described in example of cell n°. 1.

Figure 5 - Polarisation curves of two direct ethylene glycol fuel cells (DGFC) a and b for the cell described in example of cell n°. 2.

Figure 6 - Durability test at constant power for the DGFC cells a and b with the characteristics described in example of cell n°. 2.

Figure 7 - Polarization curves of two DEFC cells a and b for the cell described in example of cell of n°. 3. Figure 8 - Polarisation curves of two direct ethanol fuel cells (DEFC) a and b for the cell described in example of cell n°. 3.

Figure 9 - Polarisation curves of two direct ethanol fuel cells (DEFC) a and b for the cell described in example of cell n°. 4.

Figure 10 - Durability test at constant power for the DGFC cells a and b with the characteristics described in example of cell n°. 4.

Figure 1 1 - Polarisation curves of two DGFC fuel cells a and b for the cell described in example of cell n°. 5.

Figure 12 - Durability test at constant power for the DGFC cells a and b with the characteristics described in example of cell n°. 5. Figure 13 - Polarisation curves of two direct methanol fuel cells (DMFC) a and b for the cell described in example of cell n°. 6.

Figure 14 - Durability test at constant power for the DMFC cells a and b with the characteristics described in example of cell n°. 6.

Figure 15 - Durability test at constant power for the DEFC cells a and b with the characteristics described in example of cell n°. 7.

Figure 16 - Durability test at constant power for the DEFC cells a and b with the characteristics described in example of cell n°. 7.

Detailed description of the invention

The invention enables the improvement in stability and performance of anodic electrocatalysts in fuel cells fed by combined hydrogen, in particular with alcohols like ethanol, ethylene glycol and with carbohydrates like glucose and sucrose.

State of the art anodic electrocatalysts for such fuel cells lose efficiency when functioning due to a number of phenomenon: formation of thick oxide or hydroxide layers on the catalyst surface; slow desorption and adsorption of reagents; formation of surface species capable of poisoning the catalyst active sites. The formation of surface oxides is often inevitable, even when the catalyst is not working, when the catalysts are of nanometric dimensions and are made up of mainly non-noble metals as in the case of HYPERMEC^® catalysts. These effects are more or less common to all state of the art catalysts, even those based on noble metals, especially when utilised for the electro-oxidation of alcohols of a higher molecular weight compared to methanol, like ethanol or ethylene glycol.

In the case of the formation of surface oxides, the catalytic activity is usually regenerated by the application of potential cycling around the value of surface oxide formation or by the addition of reducing agents like alkaline borohydrides. Both processes are not utilisable in fuel cells: the first for obvious reasons, the second because alkaline borohydrides, like sodium borohydride, are unstable in aqueous solution.

At present, there are no general methods for preventing the formation/adsorption on the catalyst surface of species capable of inhibiting the electro-oxidation of desired substrates in fuel cells. We have surprisingly discovered, and demonstrated in this invention, that the spontaneous deposition of small quantities of a noble metal, preferably palladium or platinum, onto state of the art nanostructured catalysts for anodes in DFC cells, has an activating and stabilising effect in comparison to the nanostructured catalysts particularly those comprised of non noble metals like Iron, Cobalt and Nickel.

This activating/stabilising effect has been proved for a series of non noble metal anodic catalysts, for example based on Ni-Fe-Co, Ni-Co alloys and Ni only. The stoichiometric ratio between the total metals in the preformed nanostructured catalysts and the deposited noble metal can vary between 20:1 and 1 :0.5, with metal loadings on the electrode between 0.1 and 5 mg/cm².

In this range of stoichiometric ratio between metals, the use of the catalysts described in this invention leads to an improved in both activity and the stability of the catalyst.

In particular, it has been observed that improvements can be obtained in peak power of between 5 and 50%, and in some cases higher, and in duration of function, regardless of the fuel, generally superior to 100% with ethanol, ethylene glycol and methanol.

It could be thought that the noble metal begins the fuel oxidation reaction, sparking in this way the formation of an electron rich environment, and hence reducing, around the preformed catalyst metal particles that act also as a support for the noble metal catalyst. The present invention allows the realisation of new anodic catalysts for fuel cells obtained by a synthetic procedure that involves the spontaneous deposition of a noble metal, preferably Pd or Pt, on preformed nanostructured catalysts, as example those known by the trademark HYPERMEC^® based upon Iron, Cobalt and Nickel, alone or in binary and ternary combinations. The nanostructured catalyst in which are deposited the noble metal are prepared from metal complexes formed from transition metal salts preferably Fe, Co and Ni, and templating polymers (already described in WO2004/036674) obtained from the condensation of a 1 ,3-diolo, containing a coordinating nitrogen, with phenol or a 3,5 substituted phenol and formaldehyde or paraformaldehyde in the presence of an acidic or basic catalyst in water/alcohol mixtures and at temperatures between 20 and 150 with a resulting molecular weight between 1000 and 50000. Once the complexation of the metal salts by the templating resin has been followed, the metallised resin is adsorbed onto a conducting carbon support. The material thus obtained is reduced by state of the art methods, like treatment with gaseous hydrogen at high temperature or the reduction in suspension in a solvent by using other chemical reductants like alkaline borohydrides. The applicant has surprisingly found that the above described nanostructured catalysts generate anodic catalysts for direct alcohol fuel cells much more stable and efficient than themselves and in general other state of the art catalysts for DFC type fuel cells when they are treated with noble metal salts.

In particular, the nanostructured catalysts are suspended in water and to this suspension are added a noble metal salt, preferably Pd, Pt, Rh, Ru, Ir, Au, Ag. The resulting product is then reduced in the solid state with gaseous hydrogen at high temperature, preferably between 300 and 400 °C, or with state of the art reducing agents like NaBH₄, if suspended in a solvent like water, ethanol or acetone. The noble metal salts according to this invention are chosen from the group of carboxylates, halides, alcoholates, acetyl aceto nates, formates, oxalates, malonates and analogous organic salts and their mixtures or carbon oxides and bicarbonates and their mixtures. For the preparation of the catalysts described in this invention for use in preparing anodes for fuel cells methods 1 -3 can be used indifferently as described below. Method 1

A salt or nickel compound, preferably nickel acetate tetrahydrate [Ni(CH₃CO₂)₂-4H₂O] dissolved in water is added to an aqueous suspension containing a templating polymer described above in WO 2004/036674, and or PCT/EO2005/0567728, from now on known as the POLYMER. The solid product that forms is filtered, washed with water and dried. This dry solid is then added to a suspension in acetone or another organic solvent of a conductive porous graphitic or amorphous carbon, for example Vulcan XC-72 or activated carbon RDBA for name a few. The resulting product is then treated with a state of the art reducing agent e.g. NaBH₄ or NH₂NH₂, filtered, washed with water and dried or reduced under hydrogen at high temperature between 300 and 800 °C. The solid thus obtained is suspended in water and a salt or noble metal compound preferably palladium chloride (PdCI₂) or hexachloroplatinic acid (H₂PtCI₆) is added to the suspension. After an hour the material is filtered, washed with water, dried, suspended in water and reduced with a state of the art reducing agent e.g. NaBH₄ or NH₂NH₂, filtered, washed with water and dried.

Alternatively, the solid product obtained after the first filtration is treated under a current of hydrogen at high temperature between 300 and 800 °C. Method 2

A solution in water consisting of a salt or nickel compound, preferably nickel acetate tetrahydrate [Ni(CH₃CO₂)₂-4H₂O] and a salt or a cobalt compound, preferably [Co(CH₃C0₂)₂-4H₂0] is added to an aqueous suspension containing a templating polymer described above and in WO 2004/036674, and or PCT/EO2005/0567728 from now on known as POLYMER. The solid product that forms is filtered, washed with water and dried. This dry solid is then added to a suspension in acetone or another organic solvent of a conductive porous graphitic or amorphous carbon, for example Vulcan XC-72 or activated carbon RDBA for name a few. The resulting product is then treated with a state of the art reducing agent e.g. NaBH₄ or NH₂NH₂, filtered, washed with water and dried or reduced under hydrogen at high temperature between 300 and 800 °C. The solid thus obtained is suspended in water and a salt or noble metal compound preferably palladium chloride (PdCI₂) or hexachloroplatinic acid (H₂PtCI₆) is added to the suspension.

After an hour the material is filtered, washed with water, dried, suspended in water and reduced with a state of the art reducing agent e.g. NaBH₄ or NH₂NH₂, filtered, washed with water and dried.

Alternatively, the solid product obtained after the first filtration is treated under a current of hydrogen at high temperature between 300 and 800 °C.

Method 3

A solution in water consisting of a salt or nickel compound, preferably nickel acetate tetrahydrate [Ni(CH₃CO₂)₂-4H₂O], a salt or a cobalt compound, preferably [Co(CH₃CO₂)₂-4H₂O] and a salt or iron compound, preferably [Fe(CH₃CO₂)₂] is added to an aqueous suspension containing a templating polymer described above and in WO 2004/036674, and or PCT/EO2005/0567728 from now on known as POLYMER. The solid product that forms is filtered, washed with water and dried. This dry solid is then added to a suspension in acetone or another organic solvent of a conductive porous graphitic or amorphous carbon, for example Vulcan XC-72 or activated carbon RDBA for name a few. The resulting product is then treated with a state of the art reducing agent e.g. NaBH₄ or NH₂NH₂, filtered, washed with water and dried or reduced under hydrogen at high temperature between 300 and 800 °C.

The solid thus obtained is suspended in water and a salt or noble metal compound preferably palladium chloride (PdCI₂) or hexachloroplatinic acid (H₂PtCI₆) is added to the suspension.

After an hour the material is filtered, washed with water, dried, suspended in water and reduced with a state of the art reducing agent e.g. NaBH₄ or NH₂NH₂, filtered, washed with water and dried. Alternatively, the solid product obtained after the first filtration is treated under a current of hydrogen at high temperature between 300 and 800 °C.

Anode Preparation

Catalysts supported on conductive carbon prepared with methods 1 -3 are suspended in a water/alcohol mixture. To this vigorously stirred suspension, is added PTFE (polythetrafluoroethylene) and the flocculant material obtained is separated and then spread onto a conductive support like carbon paper, steel or nickel mesh. The electrode is then heated to 350 °C in a flow of inert gas (Ar, N₂).

To better understand the invention some examples are provided below of anode preparation. Example 1

PREPARATION OF A IRON, COBALT, NICKEL AND PALLADIUM BASED

ANODIC CATALYST

To a suspension containing 7 g of a polymer defined previously as POLYMER in

440 mL of water and 87.5 mL of NaOH 1 M, finely dispersed using an ultrasound probe for 30 min., are added 3.18 g of nickel acetate tetrahydrate

[Ni(CH₃CO₂)₂-4H₂O], 3.18 g of cobalt acetate tetrahydrate [Co(CH₃CO₂)₂4H₂O] and 2.54 g of iron acetate [Fe(CH₃CO₂)₂] dissolved in 200 mL of water and the resulting mixture is stirred vigorously at room temperature over night.

The pH is then adjusted to 7.5 using HCI 1 M and the brick red precipitate that forms is filtered, washed thoroughly with water (4 X 50 mL) and dried under vacuum at 70 °C to constant weight Yield 8 g. Content: Ni = 6.22 wt%, Co = 6.44 wt% and Fe = 5.99 wt% (ICP-AES).

To a suspension of the above compound in 500 mL of acetone (finely dispersed using an ultrasound probe for 30 min.) are added 7 g of Vulcan XC-72R. The resulting mixture is dispersed with the ultrasound probe for a further 1 hour and the solvent is removed by evaporation under reduced pressure.

The mixture containing POLYMER-Fe, Ni, Co/Vulcan is introduced into a quartz furnace and then heated under a flow of hydrogen gas at 365 °C for 2 h. This solid residue is finely ground and then added to a solution of palladium chloride (PdCI₂) obtained by dissolving 0.12 g of PdCI₂ in 500 ml_ of water acidified with 0.5 ml_ of cone. HCI and heated to 40 °C. The suspension is stirred vigorously for one hour at room temperature, filtered and washed with water (300 ml_). It is then suspended in 500 ml_ of water and whilst stirring vigorously at room temperature, 2 g of NaBH₄ dissolved in water (50 ml_) is added. This suspension is kept stirred at room temperature under a flow of nitrogen gas and after 2 hours is filtered, washed with water (500 ml_) and dried under vacuum to constant weight. Ni content 1.03 wt.% Co content =1.04 wt.%, Fe content = 0.99 wt.%, Pd content = 1.06 wt.% (ICP-AES). Atomic percentage ratio: Ni₂₅Co₂₅Fe₂₅Pd₂₅ Example 2 PREPARATION OF A COBALT, NICKEL AND PALLADIUM BASED ANODIC CATALYST

To a suspension containing 7 g of a polymer defined previously as POLYMER in 437.5 mL of water and 87.5 mL of NaOH 1 M, finely dispersed using an ultrasound probe for 30 min., are added 3.18 g of nickel acetate tetrahydrate [Ni(CH₃CO₂)₂-4H₂O] and 3.18 g of cobalt acetate tetrahydrate [Co(CH₃CO₂)^H₂O] dissolved in 150 mL of water and the resulting mixture is stirred vigorously at room temperature over night.

The pH is then adjusted to 7.5 using HCI 1 M and the brick red precipitate that forms is filtered, washed thoroughly with water (4 X 50 mL) and dried under vacuum at 70 °C to constant weight. Yield 8 g. Content: Ni = 6.82 wt%, Co = 6.67 wt% (ICP-AES).

To a suspension of 1.3 g of the above compound in 500 mL of acetone (finely dispersed using an ultrasound probe for 30 min.) are added 7 g of Vulcan XC-72R. The resulting mixture is dispersed with the ultrasound probe for a further 1 hour and the solvent is removed by evaporation under reduced pressure. The mixture containing POLYMER-Fe, Ni, Co/Vulcan is introduced into a quartz furnace and then heated under a flow of hydrogen gas at 365 °C for 2 h. This solid residue is finely ground and then added to a solution of palladium chloride (PdCI₂) obtained by dissolving 0.12 g of PdCI₂ in 500 ml_ of water acidified with 0.5 ml_ of cone. HCI (37%) and heated to 40 °C.

The suspension is stirred vigorously for one hour at room temperature, filtered and washed with water (500 ml_). It is then suspended in 500 ml_ of water and whilst stirring vigorously at room temperature, 2 g of NaBH₄ dissolved in water (50 ml_) is added. This suspension is kept stirred at room temperature under a flow of nitrogen gas and after 2 hours is filtered, washed with water (500 ml_) and dried under vacuum to constant weight. Ni content 1.12 wt.% Co content =1.13 wt.%, Pd content = 1.07 wt.% (ICP-AES). Atomic percentage ratio: Ni₃33Co₃33Pd₃33- Example 3

PREPARATION OF A NICKEL AND PALLADIUM BASED ANODIC CATALYST To a suspension containing 7 g of a polymer defined previously as POLYMER in 437.5 mL of water and 87.5 mL of NaOH 1 M, finely dispersed using an ultrasound probe for 30 min., are added 9.54 g of nickel acetate tetrahydrate [Ni(CH₃CO₂)₂"4H₂O] in 150 mL of water and the resulting mixture is stirred vigorously at room temperature over night.

The pH is then adjusted to 7.5 using HCI 1 M and the brick red precipitate that forms is filtered, washed thoroughly with water (4 X 50 mL) and dried under vacuum at 70 °C to constant weight Yield 8 g. Content: Ni = 15.82 wt% (ICP-AES). To a suspension of 3 g of the above compound in 500 mL of acetone (finely dispersed using an ultrasound probe for 30 min.) are added 2.5 g of Vulcan XC- 72R. The resulting mixture is dispersed with the ultrasound probe for a further 1 hour and the solvent is removed by evaporation under reduced pressure. The solid residue thus obtained is suspended in 500 mL of water and finely dispersed using an ultrasonic probe for 10 min. This mixture stirred vigorously under a flow of nitrogen, is cooled to 0 °C, and 3 g of NaBH₄ dissolved in water (50 mL) is added in small portions. After 2 hours the solid residue is filtered, washed first with water (2 x 500 mL), then with KOH 0,1 M (4 x 100 mL) and finely with (2 x 200 mL). The product is dried under vacuum at 25 °C to constant weight. Ni content = 12.22 wt.% (ICP-AES).

Alternatively, the reduction can be obtained using a reactor under 1 bar of hydrogen. In this case 3 g of the compound Polymer-Ni/Vulcan is introduced in a quartz furnace and heated to 360 °C for 2 h.

This solid residue is finely ground and then added to a solution of palladium chloride (PdCI₂) obtained by dissolving 0.13 g of PdCI₂ in 500 ml_ of water acidified with 0.5 ml_ of cone. HCI (37%) and heated to 40 °C. The suspension is stirred vigorously for one hour at room temperature, filtered and washed with water (500 ml_). It is then suspended in 500 ml_ of water and whilst stirring vigorously at room temperature, 2 g of NaBH₄ dissolved in water (50 ml_) is added. This suspension is kept stirred at room temperature under a flow of nitrogen gas and after 2 hours is filtered, washed with water (500 ml_) and dried under vacuum to constant weight. Nickel content 12.58 wt.%, content of Pd = 1.09 (ICP-AES). Atomic percentage ratio : Ni₉₃Pd₇ Example 4

PREPARATION OF A IRON, COBALT, NICKEL AND PLATINUM BASED ANODIC CATALYST To a suspension containing 7 g of a polymer defined previously as POLYMER in 440 mL of water and 87.5 mL of NaOH 1 M, finely dispersed using an ultrasound probe for 30 min., are added 3.18 g of nickel acetate tetrahydrate [Ni(CH₃CO₂)₂-4H₂O], 3.18 g of cobalt acetate tetrahydrate [Co(CH₃CO₂)₂4H₂O] and 2.54 g of iron acetate [Fe(CH₃CO₂)₂] dissolved in 200 mL of water and the resulting mixture is stirred vigorously at room temperature over night.

The pH is then adjusted to 7.5 using HCI 1 M and the brick red precipitate that forms is filtered, washed thoroughly with water (4 X 50 mL) and dried under vacuum at 70 °C to constant weight Yield 8 g. Content: Ni = 6.22 wt%, Co = 6.44 wt% and Fe = 5.99 wt% (ICP-AES). To a suspension of the above compound in 500 mL of acetone (finely dispersed using an ultrasound probe for 30 min.) are added 7 g of Vulcan XC-72R. The resulting mixture is dispersed with the ultrasound probe for a further 1 hour and the solvent is removed by evaporation under reduced pressure. The mixture containing POLYMER-Fe, Ni, Co/Vulcan is introduced into a quartz furnace and then heated under a flow of hydrogen gas at 365 °C for 2 h. This solid residue is finely ground and then added to a solution of hexachloroplatinic acid (K₂PtCI₄) obtained by dissolving 0.14 g of K₂PtCI₄ in 500 mL of water acidified with 0.5 ml_ of cone. HCI and heated to 40 °C.

The suspension is stirred vigorously for one hour at room temperature, filtered and washed with water (300 ml_). It is then suspended in 500 ml_ of water and whilst stirring vigorously at room temperature, 2 g of NaBH₄ dissolved in water (50 ml_) is added. This suspension is kept stirred at room temperature under a flow of nitrogen gas and after 2 hours is filtered, washed with water (500 ml_) and dried under vacuum to constant weight. Ni content 1.03 wt.% Co content =1.04 wt.%, Fe content = 0.99 wt.%, Pd content = 1.06 wt.% (ICP-AES). Atomic percentage ratio: Fe₂₅Co₂₅Ni₂₅Pt₂₅. Example 5

PREPARATION OF A COBALT, NICKEL AND PLATINUM BASED ANODIC

CATALYST

To a suspension containing 7 g of a polymer defined previously as POLYMER in

437.5 mL of water and 87.5 mL of NaOH 1 M, finely dispersed using an ultrasound probe for 30 min., are added 2.5 g of nickel acetate tetrahydrate [Ni(CH₃CO₂)2-4H₂O] and 2.5 g of cobalt acetate tetrahydrate [Co(CH₃CO₂)₂4H₂O] dissolved in 150 mL of water and the resulting mixture is stirred vigorously at room temperature over night. The pH is then adjusted to 7.5 using HCI 1 M and the brick red precipitate that forms is filtered, washed thoroughly with water (4 X 50 mL) and dried under vacuum at 70 °C to constant weight Yield = 7 g. Ni = 5.31 wt.%, Co = 5.28 wt.% (ICP-AES).

To a suspension of 1.3 g of the above compound in 500 mL of acetone (finely dispersed using an ultrasound probe for 30 min.) are added 5 g of Vulcan XC-72R. The resulting mixture is dispersed with the ultrasound probe for a further 1 hour and the solvent is removed by evaporation under reduced pressure. The mixture containing POLYMER-Fe, Ni, Co/Vulcan is introduced into a quartz furnace and then heated under a flow of hydrogen gas at 365 °C for 2 h. This solid residue is finely ground and then added to a solution of hexachloroplatinic acid (K₂PtCI₄) obtained by dissolving 0.13 g of K₂PtCI₄ in 500 mL of water acidified with 0.5 mL of cone. HCI and heated to 40 °C. The suspension is stirred vigorously for one hour at room temperature, filtered and washed with water (500 ml_). It is then suspended in 500 ml_ of water and whilst stirring vigorously at room temperature, 3 g of NaBH₄ dissolved in water (50 ml_) is added. This suspension is kept stirred at room temperature under a flow of nitrogen gas and after 2 hours is filtered, washed with water (500 ml_) and dried under vacuum to constant weight. Ni content 1.03 wt.% Co content =1.04 wt.%, Pt content = 1.1 wt.% (ICP-AES). Atomic percentage ratio: Ni_{33 3}Co_{33 3}Pt_{33 3}. Example 6

PREPARATION OF A NICKEL AND PLATINUM BASED ANODIC CATALYST To a suspension containing 7 g of a polymer defined previously as POLYMER in 437.5 mL of water and 87.5 mL of NaOH 1 M, finely dispersed using an ultrasound probe for 30 min., are added 9.54 g of nickel acetate tetrahydrate [Ni(CH₃CO₂)₂-4H₂O] in 150 mL of water and the resulting mixture is stirred vigorously at room temperature over night. The pH is then adjusted to 7.5 using HCI 1 M and the brick red precipitate that forms is filtered, washed thoroughly with water (4 X 50 mL) and dried under vacuum at 70 °C to constant weight Yield 8 g. Content: Ni = 14.5 wt% (ICP-AES). To a suspension of 3 g of the above compound in 500 mL of acetone (finely dispersed using an ultrasound probe for 30 min.) are added 2.5 g of Vulcan XC- 72R. The resulting mixture is dispersed with the ultrasound probe for a further 1 hour and the solvent is removed by evaporation under reduced pressure. The solid residue thus obtained is suspended in 500 mL of water and finely dispersed using an ultrasonic probe for 10 min. This mixture stirred vigorously under a flow of nitrogen, is cooled to 0 °C, and 3 g of NaBH₄ dissolved in water (50 mL) is added in small portions. After 2 hours the solid residue is filtered, washed first with water (2 x 500 mL), then with KOH 0,1 M (4 x 100 mL) and finely with (2 x 200 mL). The product is dried under vacuum at 25 °C to constant weight. Ni content = 12.1 1 wt.% (ICP-AES).

This solid residue is finely ground and then added to a solution of hexachloroplatinic acid (K₂PtCI₄) obtained by dissolving 0.13 g of K₂PtCI₄ in 500 ml_ of water acidified with 0.5 ml_ of cone. HCI and heated to 40 °C.

The suspension is stirred vigorously for one hour at room temperature, filtered and washed with water (500 ml_). It is then suspended in 500 ml_ of water and whilst stirring vigorously at room temperature, 2 g of NaBH₄ dissolved in water (50 ml_) is added. This suspension is kept stirred at room temperature under a flow of nitrogen gas and after 2 hours is filtered, washed with water (200 ml_) and dried under vacuum to constant weight. Nickel content 12.1 1 wt.%, content of Pt = 1.09

(ICP-AES). Atomic percentage ratio: Ni₉₃Pt₇.

Examples of cells made with anodes containing the catalysts of this invention, and also for comparison, cells made with other state of the art anodic catalysts. The power curves and the galvanostatic experiments were carried out with a potenziostat/galvanostat (Princeton PARSTAT 2273).

Example of cell n. ° 1

Cell a: 1 Cathode HYPERMEC^® Fe₅₀-Co₅₀, total metal loading: 90 microgram/cm².

2 Membrane Tokuyama A006

3 Anode HYPERMEC^® Ni₃₃ SCo₃S sFe₃₃ S, total metal loading: 0.2 mg/cm².

4 Dimensions of the membrane electrode assembly (MEA): 5 cm².

5 Composition and volume (10 ml_) of fuel: ethanol 10 wt%; 1 M KOH Cell b:

1 Cathode HYPERMEC^® Fe₅₀-Co₅₀, total metal loading: 90 microgram/cm².

2 Membrane Tokuyama A006

3 Anode described in example 1 , Ni₂₅Co₂₅Fe₂₅Pd₂₅ , total metal loading: 0.2 mg/cm². 4 Dimensions of the membrane electrode assembly (MEA): 5 cm².

5 Composition and volume (10 ml_) of fuel: ethanol 10 wt%; 1 M KOH

Example of cell n. ° 2

Cell a:

1 Cathode HYPERMEC^® Fe₅₀-Co₅₀, total metal loading: 90 microgram/cm². 2 Membrane Tokuyama A006

3 Anode HYPERMEC^® Ni₅₀Co₅₀, total metal loading: 0.2 mg/cm².

4 Dimensions of the membrane electrode assembly (MEA): 5 cm². 5 Composition and volume (10 ml_) of fuel: ethylene glycol 10 wt%; 1 M KOH Cell b:

1 Cathode HYP ERM EC^® Fe₅₀-Co₅₀, total metal loading: 90 microgram/cm².

2 Membrane Tokuyama A006 3 Anode described in example 2, Ni_{33 3}Co_{33 3}Pd₃₃₃ total metal loading: 0.2 mg/cm².

4 Dimensions of the membrane electrode assembly (MEA): 5 cm².

5 Composition and volume (10 ml_) of fuel: ethylene glycol 10 wt%; 1 M KOH Example of cell n. ° 3

2 Membrane Tokuyama A006

3 Anode HYPERMEC^® Ni₁₀₀ total metal loading: 0.2 mg/cm².

4 Dimensions of the membrane electrode assembly (MEA): 5 cm².

5 Composition and volume (10 ml_) of fuel: ethanol 10 wt%; 1 M KOH Cell b:

2 Membrane Tokuyama A006

3 Anode described in example 3, Ni₉₃Pd₇, total metal loading: 0.2 mg/cm².

4 Dimensions of the membrane electrode assembly (MEA): 5 cm². 5 Composition and volume (10 ml_) of fuel: ethanol 10 wt%; 1 M KOH

Example of cell n. ° 4 Cell a:

2 Membrane Tokuyama A006 3 Anode HYPERMEC^® Ni₃₃Co₃₃Fe₃₃ , total metal loading: 0.2 mg/cm².

4 Dimensions of the membrane electrode assembly (MEA): 5 cm².

5 Composition and volume (10 ml_) of fuel: ethanol 10 wt%; 1 M KOH Cell b:

3 Anode described in example 4, Ni₂₅Co₂₅Fe₂₅Pt₂₅ , total metal loading: 0.2 mg/cm². 4 Dimensions of the membrane electrode assembly (MEA): 5 cm².

5 Composition and volume (10 ml) of fuel: ethanol 10 wt%; 1 M KOH Example of cell n. ° 5

Cell a: 1 Cathode HYP ERM EC^® Fe₅₀-Co₅₀, total metal loading: 90 microgram/cm².

2 Membrane Tokuyama A006

3 Anode HYPERMEC^® Ni₅₀Co₅₀ , total metal loading: 0.2 mg/cm².

4 Dimensions of the membrane electrode assembly (MEA): 5 cm².

5 Composition and volume (10 ml_) of fuel: ethylene glycol 10 wt%; 1 M KOH Cell b:

2 Membrane Tokuyama A006

3 Anode described in exampleδ, Ni_{33 3}Co_{33 3}Pt₃₃₃ total metal loading: 0.2 mg/cm².

4 Dimensions of the membrane electrode assembly (MEA): 5 cm². 5 Composition and volume (10 ml_) of fuel: ethylene glycol 10 wt%; 1 M KOH Example of cell n. ° 6 Cell a:

2 Membrane Tokuyama A006 3 Anode HYPERMEC^® Ni₅₀Co₅₀, total metal loading: 0.2 mg/cm².

4 Dimensions of the membrane electrode assembly (MEA): 5 cm².

5 Composition and volume (10 ml_) of fuel: methanol 10 wt%; 1 M KOH Cell b:

3 Anode described in example 5, Ni_{33 3}Co_{33 3}Pt₃₃₃, total metal loading: 0.2 mg/cm².

4 Dimensions of the membrane electrode assembly (MEA): 5 cm².

5 Composition and volume (10 ml_) of fuel: methanol 10 wt%; 1 M KOH Example of cell n. ° 7

Cell a:

3 Anode HYPERMEC^® Ni₁₀₀ total metal loading: 0.2 mg/cm².

4 Dimensions of the membrane electrode assembly (MEA): 5 cm².

5 Composition and volume (10 ml_) of fuel: ethanol 10 wt%; 1 M KOH Cell b:

2 Membrane Tokuyama A006

3 Anode described in Example 6, Ni₉₃Pt₇, total metal loading: 0.2 mg/cm².

Claims

1. Nanostructured anodic catalysts comprising transition metals onto which noble metals have been spontaneously deposited.

2. Anodic catalysts according to claim 1 in which said transition metals are non-noble metals and said noble metals are chosen from the group consisting of Pd, Pt, Rh, Ru, Ir, Au, Ag.

3. Catalysts according to claim 2 in which the said noble metals are palladium or platinum.

4. Catalysts according to claim 2 in which the said non noble metals are chosen from the group consisting of Ni, Fe and Co only or their binary or ternary alloys.

5. Catalysts according to claim 4 in which the stoichiometric ratio between the total metals in the preformed nanostructured catalysts and the noble metal deposited varies from 20:1 to 1 :0.5, with a metal loading on the electrode variable from 0.1 to 5 mg/cm².

6. Catalysts according to the claims 1 -5 in which the said anodic nanostructured catalysts are made from templating polymers obtained by the condensation of an 1 ,3-diol, containing a coordinating nitrogen with phenol or a 3,5 substituted phenol and formaldehyde or paraformaldehyde in the presence of an acidic or basic catalyst in water/alcohol mixtures at a temperature between 20 and 150 °C, with a resulting molecular weight from 1000 to 50000.

7. Process for the preparation of catalysts according to the claims 1 - 6 in which the nanostructured catalysts are suspended in water and to this suspension is added a noble metal salt, the resulting product is then reduced in the solid state with hydrogen gas at high temperature, from 300 to 400 °C, or with other state of the art reducing agents like NaBH₄ when said resulting product is suspended in a solvent like water, alcohol or acetone.

8. Process according to claim 7 in which:

- the noble metal salt or noble metal compound dissolved in water is added to an aqueous suspension, made basic by the addition of NaOH, of the templating polymer and the solid product formed is filtered, washed with water and dried.

- the dried solid is added to a suspension in acetone or other organic solvent of a porous conductive material based on graphitic or amorphous carbon and the resulting product is treated with a reducing agent, washed with water and dried, or is reduced in a current of hydrogen at temperatures between 300 and 800 °C;

- the solid obtained is suspended in water and a noble metal compound or a noble metal salt is added to the suspension and after about one hour the material is filtered, washed with water and dried.

- Alternatively, the solid product obtained after the first filtration is treated under a current of hydrogen at a temperature between 300 and 800 °C;

9. The process according to claim 7 in which:

- an aqueous solution comprised of two or more non noble metal salts or non noble metal compounds is added to an aqueous suspension made basic by the addition of NaOH containing the templating polymer and the solid product that forms is filtered, washed with water and dried; the dried solid is added to a suspension in acetone or other organic solvent of a porous conductive material based on graphitic or amorphous carbon and the resulting product is treated with a reducing agent, washed with water and dried, or is reduced in a current of hydrogen at temperatures between 300 and 800

⁰C;

- The solid obtained is suspended in water and a noble compound or salt is added to the suspension and after about one hour the material is filtered, washed with water and dried.

- Alternatively, the solid product obtained after the first filtration is treated under a current of hydrogen at a temperature between 300 and 800 °C.

10. Anodic catalysts according to claims 1 - 6 containing: Ni, Co, Fe and Pd in which the total weight varies from 1 % to 50% in weight with respect to the support and the atomic ratio between the four metals can be varied as pleases.

11. Anodic catalysts according to claims 1 - 6 containing: Ni, Co, Fe and Pd in which the total weight varies from 1 % to 50% in weight with respect to the support and the metals have the same percentage atomic ratio : Ni₂₅Co₂₅Fe₂₅Pd₂₅.

12. Anodic catalysts according to claims 1 - 6 containing: Ni, Co and Pd in which the total weight varies from 1 % to 50% in weight with respect to the support and the atomic ratio between the three metals can be varied as desired.

13. Anodic catalysts according to claims 1 - 6 containing: Ni, Co and Pd in which the total weight varies from 1 % to 50% in weight with respect to the support and the metals have the same percentage atomic ratio: Ni_{33 3}Co_{33 3}Pd₃₃₃.

14. Anodic catalysts according to claims 1 - 6 containing: Ni and Pd in which the total weight varies from 1 % to 50% in weight with respect to the support and the atomic ratio between the two metals can be varied as desired.

15. Anodic catalysts according to claims 1 - 6 containing: Ni and Pd in which the total weight varies from 1 % to 50% in weight with respect to the support and the metals have the percentage atomic ratio: Ni₉₃Pd₇

16. Anodic catalysts according to claims 1 - 6 containing: Ni, Co, Fe and Pt in which the total weight varies from 1 % to 50% in weight with respect to the support and the atomic ratio between the four metals can be varied as desired.

17. Anodic catalysts according to claims 1 - 6 containing: Ni, Co, Fe and Pt in which the total weight varies from 1 % to 50% in weight with respect to the support and the metals have the same percentage atomic ratio : Ni₂₅Co₂₅Fe₂₅Pt₂₅.

18. Anodic catalysts according to claims 1 - 6 containing: Ni, Co and Pt in which the total weight varies from 1 % to 50% in weight with respect to the support and the atomic ratio between the three metals can be varied as desired.

19. Anodic catalysts according to claims 1 - 6 containing: Ni, Co and Pt in which the total weight varies from 1 % to 50% in weight with respect to the support and the metals have the same percentage atomic ratio: Ni_{33 3}Co_{33 3}Pt₃₃₃.

20. Anodic catalysts according to claims 1 - 6 containing: Ni and Pt in which the total weight varies from 1 % to 50% in weight with respect to the support and the atomic ratio between the two metals can be varied as desired.

21. Anodic catalysts according to claims 1 - 6 containing: Ni and Pt in which the total weight varies from 1 % to 50% in weight with respect to the support and the metals have the percentage atomic ratio: Ni₉₃Pt₇

22. Anodes containing the catalysts according to the claims 1 - 6 and 1 1 - 21.

23. Process for the preparation of the anodes according to claim 22 in which:

- the catalysts, supported on a conductive carbon material, prepared according to claims 7 - 9 are suspended in a water/ethanol mixture:

- to the suspension, vigorously stirred, is added PTFE (polytetrafluoroethylene) and the flocculous product that separates is spread onto a conductive support like carbon paper, nickel or steel mesh.

- the electrode thus obtained is heated to 350 °C under a flow of inert gas (Ar, N2).

24. Fuel cells containing an anode according to claim 22.