Advanced Multi-Metallic SOFC Anode Development by Mechanical Alloying Route

Abstract

Anodes composed of Ni-YSZ (yttria-stabilised zirconia) cermets are the key material to allow direct biofuel feeding to Solid Oxide Fuel Cell (SOFC) devices due to its internal reforming capability. The main challenge among these materials is related to carbon deposition poisoning effect when C-bearing fuels are feed. The work deals with these issues by alloying Ni with some metals like Cu to conform a multi-metallic anode material. Mechanical alloying (MA) at shaker mills is chosen as the route to incorporate the metal and ceramic powders in the anode material, also leading to better sintering behaviour. A projected cermet material is conceived where a third metal can be added based on two criteria: low Cu solubility and similar formation enthalpy of hydrides regarding Ni. Refractory metals like Nb, W and Mo, seems to fulfil these characteristics, as well as Ag. The MA resulted powder morphology is highly homogeneous showing nanometric interpolated metal lamellae. The sintering behaviour is investigated by conventional dilatometry as well as by stepwise isothermal dilatometry (SID) quasi-isothermal method to determine the sintering kinetic parameters. Based on these tools, it is found the Cu additive promotes sintering to obtain a denser anode and therefore allowing lower process temperatures. The consolidation is achieved through the sintering by activated surface (SAS) method allied to liquid phase sintering process, where the third metal additive also has influenced. The final cermet can be obtained at one sole process step, dispensing pore-forming additives and reduction treatments. The sintered microstructure demonstrates the material is homogeneous and possesses suitable percolation networks and pore structure for SOFC anode applications.

Catalysis Using Metal Oxides with Mixed Ionic -Electronic Conductivity for Clean Energy Electrochemical Systems

“…Direct bio-fuel solid oxide fuel cells (SOFCs) can play a key role in reducing greenhouse gases, reducing U.S. dependence on imported oil and moving us toward future energy independence [1][2][3][4][5][6][7][8][9]. Direct bio-fuel SOFCs can directly convert the chemical energy of bio-derived fuels into electrical energy as shown in Figure 1(A) [1,2].…”

“…Direct bio-fuel SOFCs can directly convert the chemical energy of bio-derived fuels into electrical energy as shown in Figure 1(A) [1,2]. In order to efficiently operate them, it is critical to develop a high-performance anode that can directly process bio-fuels [1][2][3][4]. Metal oxides with mixed conductivities, which transport both ions and electrons in a single phase, can be used as anodes for this application [5][6][7][8][9][10][11][12][13][14].…”

“…Thus, the bio-fuel oxidation activity and selectivity are strongly influenced by the molecular structure of bio-fuels. A SOFC is an all-ceramic device that typically operates in the range 700-1000 ᴼC [1][2][3][4]. Unlike low temperature polymer electrolyte membrane-(PEM) fuel cells, SOFCs hold particular promise for their ability to use CO as a fuel rather than being poisoned by it [48][49][50][51].…”

Obtenção do cermet Ni-ZrO2 por moagem de alta energia

“…Desta forma, o controle dos parâmetros no processamento do Cermet são muito importantes para aperfeiçoar o desempenho do material do anodo da célula a combustível de óxido sólido [26] .…”

“…Após secagem, foram preparadas misturas de níquel e zircônia considerando as concentrações previamente definidas, visando a percolação elétrica, para uso em SOFC [10,26] .…”