Highly Efficient Oxygen Electrode Design for Anion-Exchange Membrane-Unitized Regenerative Fuel Cells

Designing highly efficient oxygen electrodes is crucial for the development of anion-exchange membrane-unitized regenerative fuel cells (AEM-URFCs) that operate in both water-electrolysis (WE) and fuel-cell (FC) modes. In this article, we introduce a suitable oxygen electrode design that includes oxygen- evolution-reaction (OER) and oxygen-reduction-reaction (ORR) catalysts that exhibit high WE and FC performance. We first investigated three different oxygen electrodes, one with a single layer comprising a mixture of two catalysts, and the others with dual layers comprising separate layers. The AEMURFC with the ORR catalyst as the inner layer and the OER catalyst as the outer layer exhibited excellent WE and FC performance, leading to high round-trip efficiencies. In addition, the effects of the OER- and ORR-catalyst loadings on the oxygen electrode were examined. The resulting optimal AEM-URFC yielded the highest round-trip efficiency of 62% at 20 mA cm among researched AEM-URFCs. In addition, the developed AEM-URFC exhibited durable WE and FC performance over 50 h.