Thermodynamic Modeling and Testing of the H₂/O₂/Ni/NiO System

Alternative Title

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.


Mechanical and Aerospace Engineering

Second Department

Materials Science and Engineering

Keywords and Phrases

SOFC; Fuel Cells; Hydrogen; Solid oxide fuel cells

Document Type

Article - Conference proceedings

Document Version


File Type





© 2007 The Minerals, Metals & Materials Society (TMS), All rights reserved.

Publication Date

01 Jan 2007

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