A nanostructured bifunctional Pd/C gas-diffusion electrode for metal-air batteries

Designing a bifunctional air electrode which catalyses both the oxygen reduction and oxygen evolution reactions is an essential part of progress towards fully rechargeable metal-air batteries, such as the iron-air battery which is environmentally friendly, low cost, and does not suffer risk of thermal runaway like lithium-ion batteries. This paper reports the development of a lightweight carbon-based bifunctional air electrode, catalysed by a small (0.5 mg cm-2) loading of 30 wt.% palladium on carbon. The Pd-catalysed air electrode showed good bifunctional activity, with 0.53 V potential difference between oxygen reduction and evolution. The Pd/C air electrode showed improved catalytic activity at high current densities (≥ 50 mA cm-2) and enhanced durability compared with two commercial Pt/C air electrodes produced by Gaskatel GmbH and Johnson Matthey. A stable oxygen evolution potential was maintained over 1,000 charge-discharge cycles