WO2009033498A1

WO2009033498A1 - Solid oxide fuel cell

Info

Publication number: WO2009033498A1
Application number: PCT/EP2007/007941
Authority: WO
Inventors: Xicola Agustin Sin; Marina Cancellier; Antonino Salvatore Arico'; Daniela La Rosa
Original assignee: Pirelli and C SpA
Current assignee: Pirelli and C SpA
Priority date: 2007-09-12
Filing date: 2007-09-12
Publication date: 2009-03-19
Anticipated expiration: 2010-03-12
Also published as: EP2205538A1

Abstract

A solid oxide fuel cell including a cathode, at least an electrolyte membrane, and an anode comprising a ceramic material and an alloy comprising nickel, at least a second metal selected from aluminium, titanium, molybdenum, cobalt, iron, chromium, copper, silicon, tungsten, niobium, and at least 0.05% by weight of a third metal selected from alkaline and alkaline earth metals.

Description

SOLID OXIDE FUEL CELL

The present invention relates to a solid oxide fuel cell, to a cermet material, and to a method for producing energy using such cell.

Solid-oxide fuel cells (SOFCs) convert chemical energy into electrical energy with high efficiency and low emission of pollutants. Although the introduction of a "green energy" might seem an attractive scenario, its implementation is beset with technical and economic difficulties.

The most common anodes materials for solid oxide fuel cells comprise nickel (Ni) cermets (ceramic and metallic composite materials) prepared by high-temperature calcination of NiO and ceramic powders, usually yttria-stabi- lized zirconia (YSZ) powders. These Ni-cermets perform with H₂ fuels and allow internal steam reforming of hydrocarbons if there is sufficient water in the feed to the anode. Because Ni catalyzes the formation of graphite fibers in dry methane, it is necessary to operate anodes at steam/methane ratios greater than 3, as from WO 00/52780 (in the name of Gas Research Institute).

S.J.A. Livermore et al. Journal of Power Sources, vol. 86 (2000), 411- 416, refers to a cermet anode for SOFC made of nickel and ceria-gadolinia (CGO). This anode performs at 600⁰C using 10% H₂/N₂ as the fuel.

A. Mϋller et al., Proc. of the 3rd European Solid Fuel Cell Forum, Nantes France, June 1998, 353-362, relate to a Ni-YSZ anode fuel cell. It is envisaged a degradation of the anode related to microstructural changes occurring during operation. The nickel particles have a mean diameter of about 0.5 μm, and are homogeneously distributed in the anode. After long term operation at high current density and fuel utilization (H₂+H₂O), the agglomeration of the nickel particles leads to a decrease of the amount of three-phase boundary (TPB), resulting in an increase in the anode losses.

A.C. Mϋller et al., HTMC IUPAC Jϋlich 2000 suggest that the degradation described by the previous document could be prevented by a multilayer anode whose divers layers differ in their microstructure to fulfill the locally dif- ferent requirements for SOFC anodes. In particular, the content of Ni and the Ni particle size should increase from first layer (that in contact with the elec- trolyte) to last layer, thus increasing electronic conductivity, TEC (Thermal Expansion Coefficient) and porosity. The YSZ content should simultaneously decrease. The cermet samples were prepared by mixing 65-85 mol% NiO powder with YSZ powder and sintering them in air at 1300⁰C for 5 hours. The particle size of the metallic portion was 0.5-8 μm.

The use of nickel as the metallic component of a cermet anode is advantageous, but its performance drops in short time, especially when a dry hydrocarbon is the fuel, due to graphite formation.

RJ. Gorte et al., Adv. Mater., 2000, vol.12, No. 19, 1465-1469, pro- pose to substitute nickel with copper (Cu) in a cermet wherein the ceramic portion is YSZ. Other components, including ceria (CeO₂), can be added to the metallic portion. In this configuration the role of CeO₂ is mainly to provide catalytic activity for the oxidation of hydrocarbons. As shown in Figure 4a of this paper, the cell prepared with Cu but without ceria exhibits poor perform- ance at 700⁰C, especially when methane is used as fuel.

E.Ruckenstein et al., Carbon dioxide reforming of methane over nickel / alkaline earth metal oxide catalysts, Applied Catalyst A: General 133 (1995) 149-161 , relate to the CO₂ reforming of CH₄ over reduced NiO/alkaline earth metal oxide catalysts, reporting a low stability for Ca and Sr, and no catalytic activity for Ba.

T.Horiuchi et al., Suppression of Carbon Deposition in the CO₂- reforming of CH₄ by adding basic metal oxides to a Ni/AI₂O₃ catalyst, Applied Catalyst A: General 144 (1996) 111-120, relate to the effect of the oxides of Na, K, Mg, and Ca on CO₂ reforming of CH₄ over Ni/AI₂O₃ catalysts, concluding that the suppression of carbon deposition resulted from the decrease in the ability of Ni catalyst for CH₄ decomposition.

The Applicant has faced the problem of providing a solid oxide fuel cell which is able to show high efficiency and to maintain its performace over time, particularly in terms of electrochemical properties in a wide range of temperatures. Moreover, the fuel cell should be able to show the above characteristics when fed with different fuels. Endurance of performance is particularly important when a dry hydrocarbon is used as fuel, since it tends to form graphite fibers on the metallic portion of the cermet anode, which eventually annihilate the fuel cell activity.

The Applicant has now found that by using a nickel alloy with one or more metals as metallic portion of a cermet anode, and by adding a certain amount of an alkaline or an alkaline earth metal to said nickel alloy, the resulting SOFC shows enduring efficiency when fuelled with different fuels, including hydrocarbons and alcohols, in a wide range of operating temperatures, and particularly at temperatures ranging from 500⁰C to 900⁰C. Particularly, when a dry hydrocarbon or alcohol is used as fuel, deposition of graphite residuals is remarkably reduced.

The present invention thus relates to a solid oxide fuel cell including

- a cathode;

- at least an electrolyte membrane, and - an anode comprising a ceramic material and an alloy comprising nickel, at least a second metal selected from aluminium, titanium, molybdenum, cobalt, iron, chromium, copper, silicon, tungsten, niobium, and at least 0.05% by weight of a third metal selected from alkaline and alkaline earth metals. Preferably, said third metal is selected from the group of sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, and barium.

More preferably, said third metal is selected from the group of rubidium, cesium, strontium and barium.

Most preferably, said third metal is selected from the group of cesium and barium.

According to the best practice of the present invention, said third metal is barium.

Preferably, said alloy comprises from 0.1 to 20% by weight of barium, and more preferably from 1 to 10% by weight of barium. Preferably, the anode of the invention comprises an alloy wherein said alloy has an average particle size not higher than 20 nm. More preferably said - A -

average particle size is not lower than 1 nm.

The alloy of the anode of the invention can show a mean surface area higher than 20 m²/g, preferably higher than 30 m²/g, and more preferably higher than 40 m²/g. Preferably in the anode of the invention the alloy has a second metal content of from about 1 % by weight to about 99% by weight, more preferably, and even more preferably from about 40% by weight to about 60% by weight.

Preferably in the anode of the present invention the alloy has a nickel content of from about 1 % by weight to about 99% by weight, more preferably from about 30% by weight to about 70% by weight, and even more preferably of about 50% by weight.

Preferably, said second metal is copper.

Said alloy can comprise an additional metal, for example, an element belonging to one of the classes from 3 to 13 of the periodic table of elements according to Chemical and Engineering News, 63(5), 27, 1985, lanthanides series included.

The ceramic material of the anode of the invention can be selected from yttria-stabilized zirconia (YSZ), cerium gadolinium oxide (CGO), samarium-doped ceria (SDC), mixed lanthanum and gallium oxides. Preferably the ceramic material is cerium gadolinium oxide (CGO).

The ceramic material of the anode of the present invention can show a particle size not higher than 50 nm, preferably from about 1 to about 25 nm.

Optionally, said ceramic material is doped with at least one cation selected from calcium, magnesium, strontium, lanthanum, yttrium, ytterbium, neodymium and dysprosium.

Optionally, the alloy of the invention comprises cerium oxide (Ceθ₂), optionally added with additives like cobalt.

The solid oxide fuel cell according to the present invention can be operated in a wide range of temperatures, usually ranging from 450⁰C to 900⁰C, and preferably from 500°C to 800⁰C In another aspect the present invention relates to a cermet comprising an alloy comprising nickel, at least a second metal selected from aluminium, titanium, molybdenum, cobalt, iron, chromium, copper, silicon, tungsten, niobium, and at least 0.05% by weight of a third metal selected from alkaline and alkaline earth metals.

Preferably, said third metal is selected from the group of sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, and barium.

More preferably, said third metal is selected from the group of rubidium, cesium, strontium and barium. Most preferably, said third metal is selected from the group of cesium and barium.

Preferably, said alloy comprises from 0.1 to 20% by weight of barium, and more preferably from 1 to 10% by weight of barium.

Both the metallic and the ceramic portion of the cermet anode of the present invention can be prepared from the corresponding metal salts, which may be compounded in a solid solution of the oxides thereof as described, for example, in WO2004/038844. Preferably, the oxides of the present invention are prepared starting from hydrosoluble salts of the desired metals which are dissolved in water and added with a chelating agent, for example, EDTA, oxalic, citric, acetic acid and the organic salts thereof, while maintaining the reaction mixture at a suitable pH, for example, higher than about 5. Oxidation is then carried out, e.g. by addition of a peroxide, such as hydrogen peroxide, and co-precipitate of amorphous metal oxides is obtained.

This co-precipitate comprises very fine amorphous particles substantially free from any crystallographic ordering as revealed by XRD (X-ray diffraction) and TEM (transmission electron microscopy) analyses. After thermal treatment of the precursor, in air or inert atmosphere, for example helium, a solid solution of the metallic oxides intimately admixed on an atomic scale, with fine particles size, is obtained. Preferably, the particle size can range from about 3 to about 20 nm, preferably from about 4 to about 7 nm, more preferably of about 5 nm.

In the case the ceramic portion of the cermet anode according to the invention is prepared through the above mentioned process, crystallization of the amorphous oxide precursor, for example at a temperature ranging between about 200⁰C and about 700⁰C, more preferably between about 300°C and about 500⁰C, can yield a ceramic with small particle size, for example ranging between about 6 and about 2nm. The preparation of the cermet anode, i.e. the material system comprising a metallic and a ceramic phase, can be carried out as follows. Amorphous mixed oxide precursor, obtained as said above, and a ceramic powder, preferably CGO or SDC, are admixed, and a slurry is prepared by dispersing the reactants in an organic solvent, for example ethanol or isopropanol, and further treated with ultrasounds. The resulting slurry is added with a solution of a barium salt, such as, for example, barium nitrate in an organic solvent, for example ethanol or isopropanol. The mixture is heated for solvent evaporation, and a reduction, for example in H₂ atmosphere, is carried out while heating, for example at a temperature ranging between about 400⁰C and about 1000°C, more preferably between about 500°C and about 800°C.

A solid oxide fuel cell of the invention can be prepared by applying said slurry of composite on an electrolyte membrane comprising a ceramic material, for example, CGO, SDC or YSZ.

A cathode for the solid oxide fuel cell of the invention can comprise a perovskite such as

wherein δ can range from 0 to 0.5. A specific example of cathode for the solid oxide fuel cell of the invention can be a Lao.6Sro.₄Feo.₈Cθo.2θ_3-δ/CGO.

The solid oxide fuel cell according to the invention displays great flexibility in the choose of the fuel to be fed with. It can performs by feeding the anode with a fuel selected from hydrogen; an alcohol such as methanol, ethanol, propanol; a hydrocarbon in gaseous form such as methane, ethane, butene; carbon dioxide, carbon monoxide, natural gas, reformed natural gas, biogas, syngas and mixture thereof, either in the presence of water or substantially dry; or an hydrocarbon in liquid form, e.g. diesel, toluene, kerosene, jet fuels (JP-4, JP-5, JP-8, etc) or a biofuel. Preferred by the present invention is substantially dry methane.

When a substantially dry fuel is fed to the anode, a direct oxidation is effected in the solid oxide fuel cell of the invention. In the case of dry methane, the reaction at the anode is the following

CH₄ + 4O²- → CO₂ + 2H₂O + 8e^" As already said above, the direct oxidation of a dry fuel such as a dry hydrocarbon yields coking phenomena (deposition of graphite fibers) at the metallic portion of the cermet thus exhausting the catalytic activity. The solid oxide fuel cell of the invention can perform by direct oxidation of a dry fuel.

In another further aspect, the present invention relates to a method for producing energy comprising the steps of:

- feeding at least one fuel into an anode side of a solid oxide fuel cell comprising:

• an anode including a ceramic material and an alloy comprising nickel, at least a second metal selected from aluminium, titanium, molybdenum, cobalt, iron, chromium, copper, silicon, tungsten, niobium, and at least 0.05% by weight of a third metal selected from alkaline and alkaline earth metals; and

• a cathode and at least an electrolyte membrane disposed between said anode and said cathode; - feeding an oxidant into a cathode side of said solid oxide fuel cell; and

- oxidizing said at least one fuel in said solid oxide fuel cell, resulting in production of energy.

The operating temperature of the solid oxide fuel cell of the invention can range from 450⁰C to 900⁰C, preferably from 500⁰C and 800⁰C. An advantage provided by low operating temperatures, such those preferred by the present invention, is the reduction of NO_x formation at the cathode. The formation of such undesired by-products is due to the reaction of the nitrogen present in the air fed at the cathode side, such reaction being related to temperature increase.

In case of operating with reformed fuel, the fuel is internally reformed at the anode side.

The invention will be further illustrated hereinafter with reference to the following examples and figures, wherein - Figures 1a and 1 b schematically illustrate fuel cell power systems;

- Figure 2 shows electrochemical polarisation curves for Ni_{0 5}Cu_{0 5}-CGO cermet anode/CGO electrolyte interface, with and without the addition of Ba₁ in dry CH₄ at the temperature of 750° - 800⁰C;

- Figure 3 shows impedance spectroscopy curves for Ni_O sCu_{0 5}-CGO cermet anode/CGO electrolyte interface, with and without the addition of Ba, in dry CH₄ at the temperature of 750° - 800⁰C;

- Figure 4 shows electrochemical polarisation curves for Ni_{0 5}Cu_{0 5}-CGO cermet anode/CGO electrolyte interface, with and without the addition of Ba, in dry CH₃OH at the temperature of 750° - 800⁰C; - Figure 5 shows impedance spectroscopy curves for Ni_{0 5}Cu_{0 5}-CGO cermet anode/CGO electrolyte interface, with and without the addition of Ba, in dry CH₃OH at the temperature of 750° - 800⁰C;

- Figure 6 shows chronoamperometry curves for Ni₀₅Cu_{0 5}-CGO cermet anode/CGO electrolyte interface with the addition of Ba, in dry CH₃OH and CH₄ at 0.3 V and 800⁰C.

Figures 1a and 1 b schematically illustrate a solid oxide fuel cell power systems. The solid oxide fuel cell (1 ) comprises an anode (2), a cathode (4) and an electrolyte membrane (3) disposed between them.

In Figure 1 a fuel generally a hydrocarbon, is fed to be converted into hydrogen as described, e.g., in "Fuel Cell Handbook", sixth edition, U.S. Dept. of Energy, 2002. Hydrogen is fed to the anode side of the solid oxide fuel cell (1 ). Cathode (4) is fed with air.

The fuel cell (1 ) produces energy in form of heat and electric power. The heat can be used in a bottoming cycle or conveyed to fuel reformer (5). The electric power is produced as direct current (DC) and may be exploited as such or converted into alternate current (AC) via a power conditioner (6).

Figure 1 b shows a preferred embodiment of the invention. A substantially dry fuel is fed to the anode (2) where direct oxidation is effected. The heat can be used in a bottoming cycle. The direct current produced is ex- ploited as such, for example in telecommunication systems.

In both the cases of Figures 1a and 1 b, from anode (2) an effluent flows which can be composed by unreacted fuel and/or reaction product/s, for example water and/or carbon dioxide in the case of Figure 1 b.

Example 1

Sinthesis of Nin sCuojO

Nio_.5Cuo_.5O was prepared from reagent graded Ni(NO₃)₂-6H₂O and Cu(NO₃)₂-6H₂O (Aldrich 99.99). Stoichiometric amounts of the metal nitrates (2.3 g of Cu(NO₃)₂-6H₂O, 3.1 g of Ni(NO₃)₂-6H₂O) were dissolved in distilled water (50 ml) and then complexed at room temperature with an aqueous solution of oxalic acid (9.5 g in 200ml; Aldrich 99.99) at pH=6.5 adjusted with NaOH 0.1 N. The molar ratio between complexing agent and the sum of the metal ions was 10. The complex formation was monitored by UV spec- troscopy. The solution was heated to 8O⁰C, and oxygen peroxide (500 ml, 20%, Carlo Erba) was then dropwise added until complete formation of a precipitate. The precipitate was filtrated, washed with distilled water, and dried at 100⁰C for 4 hours. The resulting powder was then calcinated at 500⁰C in air for 0.5 hour, to yield a crystalline phase. Example 2

Ce_I-XGd_xO_{1 95} was prepared from reagent graded Ce(NO₃)₃ 6H₂O and Gd(NO₃)₃ 6H₂O (Aldrich 99.99).

For obtaining Ce_{0 8}Gd_0-2O_1-95, 7.92 g of Ce(NO₃)₃ 6H₂O and 2,06 g of Gd(NO₃J₃ 6H₂O were dissolved in distilled water (120 ml) and then complexed at room temperature with an aqueous solution of oxalic acid (12.6 g in

1000ml; Aldrich 99.99) at pH=6.5 adjusted with NaOH 1 M. For obtaining

Ce_{0 S}Gd_{0 1}O_{1 95}, 8.99 g of Ce(NO₃)₃ 6H₂O and 1.04 g of Gd(NO₃)₃ 6H₂O were dissolved in distilled water (120 ml) and then complexed at room temperature with an aqueous solution of oxalic acid (12.6 g in 1000ml; Aldrich 99.99) at pH=6.5 adjusted with NaOH 1 M.

The precipitate was filtrated, washed with distilled water, and dried at 100°C for 4 hours. The resulting dried powder was then calcinated at 700⁰C in air for 4 hour, to yield a crystalline phase. Example 3

Preparation of Ni_n sCuo sO/CGO 0.79 g of Ceo.₉Gdo_.1O_1.95 (CGO) as prepared in example 2 and 1.00 g of Nio_.5Cuo_.5O as obtained in Example 1 were intimately mixed in an agate mortar. The mixture was put for 5 hour in a ball milling with 20 ml of ethanol, which was further ultrasonicated in order to reduce the formation of ag- glomerates. The composite was then heated to about 150⁰C for solvent evaporation, followed by reduction at about 500⁰C for 5 h under hydrogen flux. The formation of the NiCu alloy on CGO was confirmed by X-ray diffraction.

Example 4 Preparation of Nin_jCun_jO/CGO + 2%Ba

0.79 g of Ceo_.9Gdo_.1O_1.95 (CGO) as prepared in example 2 and 1.00 g of Nio_.5Cuo_.5O as obtained in Example 1 were intimately mixed in an agate mortar. The mixture was put for 5 hour in a ball milling with 20 ml of ethanol, which was further ultrasonicated in order to reduce the formation of ag- glomerates. 1g of Nio_.5Cuo_.5O/CGO was impregnated with 38 mg of Ba(NO₃)₂ dissolved in 15 ml of EtOH. The composite was then heated to about 100⁰C for solvent evaporation, followed by thermal treatment at 500⁰C for 5 h in air.

The presence of the barium in the form of BaCO₃ was confirmed by X-ray diffraction and EDX analysis. Example 5

Cell preparation

A first cell C1 was fabricated having a CGO electrolyte, a LSCFO/CGO layer as a cathode and a NiCu-CGO layer of Example 3 as an anode.

The CGO electrolyte (~300 μm, >90% theoretical density) was pre- pared by uniaxial pressing at 300 MPa of a Ceo.₈₀Gdo.₂₀O1.₉₀ powder obtained as in Example 2. Before use for pellet preparation, the powder was thermally treated at 1050⁰C for 1 h. The pellet was thermally treated at 1550°C for 3 hrs.

As the cathode, a 30 μm LSCFO was deposited by a spray process on one side of the pellet and fired at 950°C for 1 hour in air to assure good adhesion to the electrolyte. The slurry used was composed of 1 g LSCFO (Lao_.6Sro_.4Fei_-yCθ_yθ₃, Praxair) dispersed in 20 ml of isopropanol.

A 30 μm anodic cermet layer of a slurry of Nio_.5Cuo_.5O/CGO prepared according to Example 3 was deposited by spraying in one step on the CGO dense layer of the CGO-LSCFO/CGO substrate. The slurry was prepared by dispersing 1 g of Nio_.5Cuo.₅O/CGO powders in 20 ml of ethanol (Carlo Erba) that are sprayed on the electrolyte membrane. The total amount of deposited metal phase was 15 mg/cm². This was sintered at 1000⁰C for 2h in air.

A 5 μm Au (Hereus) film, to be used as the anodic current collector in the electrochemical cell, was then deposited by painting on the anodic layer, and the whole assembly was heated at 150⁰C for solvent evaporation. Two Au wires on each side were allocated for sampling current and potential.

The cells (0.25 cm² active area) were mounted on an alumina tube and sealed with quartz adhesive. Finally the system was heated at 800⁰C for 1 h in air to allow formation of a crystalline Nii_-xCu_xO₂ oxide. Inert gas (Ar) was passed through the anode before hydrogen supply. A hydrogen stream flow rate (25 cc min^"1) was fed to the anode at 800⁰C to assure the alloy formation.

Example 6 Cell preparation

Similarly, a cell C2 was fabricated having a CGO electrolyte, a LSCFO/CGO layer as a cathode and a NiCu+Ba-CGO layer of Example 4 as an anode.

The procedure was identical to that of Example 5, but a 30 μm anodic cermet layer of a slurry of Nio_.sCuo_.sO+Ba/CGO prepared according to

Example 4 was deposited by spraying in one step on the CGO dense layer of the CGO-LSCFO/CGO layer. The slurry was prepared by dispersing 1 g of

Nio.sCuo.sO+Ba/CGO powders in 20 ml of ethanol (Carlo Erba). The total amount of deposited metal phase was 15 mg/cm². This was sintered at 1000°C for 2h in air. Example 7

Characterization in half-cell configuration (dry methane fuelled anode)

Electrochemical evaluation of the performance of solid oxide fuel cells C1 and C2 fed with dry methane was carried out. The dry methane flow rate was 0.1 cc min^"1, and static air was used as oxidant. No humidification was used for the anode stream.

The cells were conditioned for at least 1 h in methane at 800⁰C before recording the polarization curves and ac-impedance spectra.

Electrochemical experiments were carried out both under galvanostatic and potentiostatic controls by using an AUTOLAB Ecochemie potentiostat/ galvanostat and impedance analyser. The polarization data were collected under steady state conditions. Ac-impedance spectra were collected in the range 1 MHz-1 mHz with a 20 mV rms sinusoidal signal under open circuit conditions. A four-electrode configuration was used in all cases. In half-cell experiments, one potential probe was connected to a non-polarized reference electrode and the overpotential of the working electrode was measured against this reference.

Fig.1 shows a clear increase of performance with the Ba addition after

3 days of work. The best power density shows 162 mW/cm2. This effect is also observed by the impedance spectroscopy showed in Fig.2. The polarisation resistance (Rp) and the total resistance (Rt) of the cell shows a clear improvement with the Ba addition. It is observed from the Nyquist diagrams that the polarization resistance (Rp) has the major impact in the cell performance. This means that the electrocatalysis is highly influenced by the anode composition showing the benefits of the Ba addition. Also, is observed the presence of C in the anode without the Ba, but it disappears with the presence of Ba.

The following Table 1 summarizes the results obtained from the electrochemical experiments. Table 1

Electrochemical evaluation of the performance of solid oxide fuel cells

C1 and C2 fed with dry methanol was carried out using the same instruments and conditions of Example 7, except as reported below.

Methanol flow rate was 50 cc min^'1, and static air was used as oxidant. No humidification was used for the anode stream. The cells were conditioned for at least 1 h in methanol at 800⁰C before recording the polarization curves and ac-impedance spectra.

As showed in Fig. 3, the electrochemical performance measured at 800°C showed after 3 days of working conditions slightly better results for the sample with Ba with respect the sample without Ba. This effect is also observed by the impedance spectroscopy showed in Fig.4. The polarisation resistance (Rp) and the total resistance (Rt) of the cell shows a clear improvement with the Ba addition. It is observed from the Nyquist diagrams that the polarization resistance (Rp) has the major impact in the cell performance. This means that the electrocatalysis is highly influenced by the anode composition showing the benefits of the Ba addition. Moreover, a big difference remains in the the amount of C deposition. It is very high in the sample without Ba and the sample with Ba showed C-free analysed by XRD and SEM (scansion electron microscopy).

The following Table 2 summarizes the results obtained from the electrochemical experiments. Table 2

Example 9

Chronoamperometry evaluation of the performance of solid oxide fuel cell C2 fed with dry methane and methanol was carried out. Chronoamperometry is an electrochemical technique in which the potential of the working electrode is stepped, and the resulting current from faradaic processes occurring at the electrode (caused by the potential step) is monitored as a function of time. The test was made using AUTOLAB Ecochemie potentiostat/galvanostat and impedance analyser at 0.3 V and 800⁰C. The sample was working for 5 days in pure methanol and pure dry methane keeping almost constant the performance after 6Oh, as showed in Fig. 6. Both samples showed absence of carbon deposition.

Claims

I . Solid oxide fuel cell including

- a cathode;

- at least an electrolyte membrane, and - an anode comprising a ceramic material and an alloy comprising nickel, at least a second metal selected from aluminium, titanium, molybdenum, cobalt, iron, chromium, copper, silicon, tungsten, niobium, and at least 0.05% by weight of a third metal selected from alkaline and alkaline earth metals.

2. Solid oxide fuel cell according to claim 1 wherein said third metal is selected from the group of sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, and barium.

3. Solid oxide fuel cell according to claim 2 wherein said third metal is selected from the group of rubidium, cesium, strontium and barium.

4. Solid oxide fuel cell according to claim 3 wherein said third metal is selected from the group of cesium and barium.

5. Solid oxide fuel cell according to claim 4 wherein said third metal is barium.

6. Solid oxide fuel cell according to claim 1 wherein said alloy comprises from 0.1 to 20% by weight of said third metal.

7. Solid oxide fuel cell according to claim 6 wherein said alloy comprises from 1 to 10% by weight of said third metal.

8. Solid oxide fuel cell according to claim 1 wherein said alloy has an average particle size not higher than 20 nm.

9. Solid oxide fuel cell according to claim 1 wherein said alloy has a mean surface area higher than 20 m²/g.

10. Solid oxide fuel cell according to claim 1 wherein said alloy has a second metal content of from 1 % by weight to 99% by weight.

I I . Solid oxide fuel cell according to claim 10 wherein said alloy has a second metal content of from 30% by weight to 70% by weight.

12. Solid oxide fuel cell according to claim 11 wherein said alloy has a second metal content of from 40% by weight to 60% by weight .

13. Solid oxide fuel cell according to claim 1 wherein said alloy has a nickel content of from 1 % by weight to 99% by weight.

14. Solid oxide fuel cell according to claim 10 wherein said alloy has a nickel content of from 30% by weight to 70% by weight.

15. Solid oxide fuel cell according to claim 11 wherein said alloy has a nickel content of from 40% by weight to 60% by weight .

16. Solid oxide fuel cell according to claim 1 wherein said second metal is copper.

17. Solid oxide fuel cell according to claim 1 wherein said ceramic material is selected from yttria-stabilized zirconia (YSZ), cerium gadolinium oxide (CGO), samarium-doped ceria (SDC), mixed lanthanum and gallium oxides.

18. Solid oxide fuel cell according to claim 1 wherein said ceramic material has a particle size not higher than 50 nm.

19. Solid oxide fuel cell according to claim 1 wherein said ceramic material has a particle size from 1 nm to 25 nm.

20. Solid oxide fuel cell according to claim 17 wherein said ceramic material is cerium gadolinium oxide (CGO).

21. Solid oxide fuel cell according to claim 1 performing in substantially dry hydrocarbon.

22. Cermet comprising a ceramic material and an alloy comprising nickel, at least a second metal selected from aluminium, titanium, molybdenum, cobalt, iron, chromium, copper, silicon, tungsten, niobium, and at least 0.05% by weight of a third metal selected from alkaline and alkaline earth metals.

23. Cermet according to claim 22 wherein said third metal is selected from the group of sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, and barium.

24. Cermet according to claim 23 wherein said third metal is selected from the group of rubidium, cesium, strontium and barium.

25. Cermet according to claim 24 wherein said third metal is selected from the group of cesium and barium.

26. Cermet according to claim 25 wherein said third metal is barium.

27. Cermet according to claim 22 wherein said alloy comprises from 0.1 to 20% by weight of said third metal.

28. Cermet according to claim 27 wherein said alloy comprises from 1 to 10% by weight of said third metal.

29. Method for producing energy comprising the steps of:

• a cathode and at least an electrolyte membrane disposed between said anode and said cathode;

- feeding an oxidant into a cathode side of said solid oxide fuel cell; and - oxidizing said at least one fuel in said solid oxide fuel cell, resulting in production of energy.

30. Method according to claim 29 wherein said at least one fuel is selected from the group comprising hydrogen, alcohol, and hydrocarbon.

31. Method according to claim 30 wherein the hydrocarbon is in gaseous or liquid form

32. Method according to claim 30 wherein the hydrocarbon is substantially dry.

33. Method according to claim 29 wherein the at least one fuel is selected from the group of dry methane and dry methanol.

34. Method according to claim 29 wherein the solid oxide fuel cell operates at a temperature ranging between from 500⁰C and 800⁰C.