Activating Ru nanoclusters for robust oxygen reduction in aqueous wide-temperature zinc-air batteries

Abstract

Aqueous wide-temperature zinc-air batteries (AWT-ZABs) have the potential to meet the fast-growing energy demand in extreme climates (−60°C to 60°C). However, cathodic oxygen reduction reaction (ORR) kinetics are susceptible to temperature fluctuations. Herein, we present a highly active and durable ORR catalyst composed of Ru nanoclusters and neighboring Mn-N₄ moieties (Ru_NC@Mn-N₄). The Ru_NC@Mn-N₄ achieved a half-wave potential of 0.925 V, surpassing known Ru-based electrocatalysts, with minimal decay after 50,000 cycles. In AWT-ZABs, the Ru_NC@Mn-N₄ delivered a peak power density (P_max) of 320.6 mW cm⁻² at 60°C and a 1.5- to 3-fold higher P_max at −20°C to −60°C compared to Pt/C. Our mechanistic investigations unveil the electron-deficient nature of Ru nanoclusters activated by the Mn-N₄ moieties, which enables the optimized adsorption/dissociation of O₂ and facilitates low-temperature protonation of intermediates, resulting in speedy wide-temperature ORR kinetics. This study sets the stage for the deliberate design of ORR electrocatalysts for optimal AWT-ZAB performance.