Thermodynamic Modeling and Testing of the H₂/O₂/Ni/NiO System
Thermodynamic modeling and testing of the H2/O2/Ni/NiO system
A reduction/oxidation cycle has been thermodynamically evaluated and measured as a proposed mechanism for degradation of single chamber solid oxide fuel cell (SC-SOFC) anodes in which an oscillation is detected in the generated voltage. The evaluated mechanism is a cycle in which the anode consumes local fuel, leaving oxygen which oxidizes the Ni, lowering the catalytic effectiveness of the anode. Fuel then diffuses into the porous anode and lowers oxygen activity, allowing NiO to reduce to Ni. This cycle is thermodynamically possible due to operating conditions near the reduction/oxidation threshold for Ni. Testing of Ni-YSZ anode under SC-SOFC operating conditions showed a periodic redox cycle that closely matched the periodic voltage cycles commonly detected during SC-SOFC operation. The proposed mechanism has been thermodynamically demonstrated to be feasible, and has been detected directly using hydrogen as a fuel while excluding carbon deposition as a mechanism for voltage oscillation.
I. D. Kellogg et al., "Thermodynamic Modeling and Testing of the H₂/O₂/Ni/NiO System," Materials Science and Technology Conference (MS&T) 2007, The Minerals, Metals & Materials Society (TMS), Jan 2007.
Mechanical and Aerospace Engineering
Materials Science and Engineering
Keywords and Phrases
SOFC; Fuel Cells; Hydrogen; Solid oxide fuel cells
Article - Conference proceedings
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