Accelerated kinetics of hydrogen oxidation reaction on the Ni anode coupled with BaZr0.9Y0.1O3-δ proton-conducting ceramic electrolyte via tuning the electrolyte surface chemistry

Abstract

Owing to the promise of proton mobility in solids, proton ceramic fuel cells (PCFCs) have demonstrated their great potential for operating at the low temperature range of 400-600˚C. For speeding up electrode reactions in PCFCs, the kinetics of the hydrogen oxidation reaction (HOR) on the Ni anode coupled with BaZr0.9Y0.1O3-δ (BZY10) proton-conducting ceramic electrolyte (abbreviated as Ni/BZY10) was investigated in correlation to the electrolyte surface chemistry. It was found that thermal annealing treatments are an effective approach to tune the surface chemistry of BZY10 (ABO3 perovskite structure) electrolytes, resulting in progressively Ba segregation toward the outer surface and enriched Y cations in B-site at subsurface. As the post-annealing temperature of BZY10 electrolytes increase from 600˚C to 1500˚C, the polarization resistance for the corresponding BZY10-based half cells decreases by a factor of 3 and 6 at the testing condition of open circuit potential and anodic overpotential, respectively. Considering a core-space-charge layer model at the Ni/BZY10 interface, the segregation of net charged Y cations (YZr') at the subsurface can partially counterbalance the positive electric potential induced by accumulation of protons in the outer surface, led to a reduced electrical potential and thus the accelerated HOR kinetics on the Ni/BZY10.