Ru-Based Catalysts Deposited by Atomic Layer Deposition for Non-Alkaline Zn-Air Batteries

Rechargeable zinc-air batteries (ZAB) are a promising energy storage solution due to their low cost, low toxicity and high theoretical energy density. However, conventional alkaline ZABs face challenges such as CO₂ absorption, zinc corrosion, and poor cycle stability. To address these issues, non-alkaline near-neutral electrolytes offer potential benefits, but they also present slower kinetics, especially during the oxygen evolution reaction (OER) at the cell charge. This study investigates the use of atomic layer deposition (ALD) to introduce Ru-based Nano-sites onto carbon cathodes to enhance catalytic activity in non-alkaline ZABs. The catalytic performance of these ALD-treated materials was evaluated in ZABs with 1 M Zn(OAc)₂ and 1 M ZnSO₄ electrolytes. ALD-treated Ru catalysts significantly lower the OER overpotentials, improving charging capacity and stability of the battery compared to pristine carbon and benchmark RuO₂/C samples with a similar content of ruthenium. We also find that with the Ru-based catalyst, OER proceeds exclusively through the four-electron pathway, in contrast to a mixture of two- and four-electron mechanisms observed for the pristine carbon. Our findings show, using a model catalytical system, that non-alkaline based ZABs can be realized through cathode engineering, and that the reaction mechanism on the cathode is highly dependent on its catalytic properties.