Progress in infiltration technology applied to air electrodes with proton-conducting electrolyte backbones

Lowering the operating temperature of solid-state energy devices to 500–700 °C has driven an increased attention being paid to protonic ceramic cells (PCCs) due to several advantages they offer such as low activation energy for proton diffusion, fuel flexibility, higher power efficiency provided by the absence of fuel dilution at the anode, as well as enhanced potential for lower housing and stacking costs. However, a significant challenge for fuel/electrolysis cells based on proton-conducting electrolytes is the performance of air electrodes for efficient oxygen reduction and water splitting reactions. The infiltration of catalysts into porous backbone layers has been demonstrated to be a highly effective method for the fabrication of highly active and durable PCC electrodes. This Focus Review summarizes the achievements in the application of the infiltration technique to the formation of air electrodes with proton-conducting electrolyte/composite backbones modified with various catalysts as a promising simple and cost-effective way to eliminate electrode/electrolyte mismatch issues and provide significant performance enhancement.