DOI:
Authors:
Seunghoe Choe, Byung-Seok Lee, Jong Hyun Jang
Abstract:
This study aims to examine the influences of substrates/diffusion layers (DL) and oxygen reduction reaction catalysts (MORR) on the performance of MORR/IrO2/DL-type bifunctional oxygen electrodes for use in polymer electrolyte membrane (PEM)-type unitized regenerative fuel cells (URFC). The MORR/IrO2/DL electrodes were prepared via two sequential steps: anodic electrodeposition of IrO2 on various DLs and fabrication of MORR layers (Pt, Pd, and Pt-Ru) by spraying on IrO2/DL. Experiments using different DLs, with Pt as the MORR, revealed that the roughness factor of the DL mainly determined the electrode performance for both water electrolyzer (WE) and fuel cell (FC) operations, while the contributions of porosity and substrate material were insignificant. When Pt-Ru was utilized as the MORR instead of Pt, WE performance was enhanced and the electrode performance was assessed by analyzing round-trip efficiencies (εRT) at current densities of 0.2 and 0.4 A/cm2. As a result, using Pt-Ru instead of Pt alone provided better εRT at both current densities, while Pd resulted in very low εRT. Improved efficiency was related to the additional catalytic action by Ru toward ORR during WE operation. Keywords: Polymer electrolyte membrane unitized regenerative fuel cell, Bifunctional oxygen electrode, Membrane electrode assembly, Diffusion layer, Electrocatalyst