Synergistic Ru–MnO ₂ Nanosheets on Carbon Nanotubes Scaffolds as a Low‐Ru Bifunctional Catalyst for High‐Performance Zinc–Air Batteries

Rechargeable zinc-air battery (ZAB) commercialization is hampered by low efficiency at the air cathodes, where sluggish kinetics and different reaction mechanisms for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) at charging and discharging state, limit overall performance. Herein, we demonstrate a carbon nanotubes-supported ruthenium-manganese dioxide (Ru-MnO₂/CNTs) as a high-performance bifunctional ZABs catalyst fabricated via in situ growth and cation exchange approach. The catalyst features a hierarchical architecture where the CNTs scaffold serves as the structural backbone, while Ru-MnO₂ solid solution nanosheets with intrinsic bifunctional activity grow conformally on its surface. This CNTs-supported design synergistically enables a low ruthenium loading of 9.1 wt% while promising electrochemical performance. Critically, the catalyst achieves an ORR half-wave potential of 0.84 V, a OER overpotential of 210 mV at 10 mA cm^-2, and a narrow OER/ORR potential gap of merely 0.6 V. When integrated into ZABs, this catalyst exhibits excellent performance, with the peak power density of 156 mW cm^-2, a high specific capacity of 802 mA h g^-1, and stable cycling performance exceeding 200 h. Consequently, this work demonstrates a viable strategy for synthesizing cost-effective and highly active bifunctional oxygen electrocatalysts with optimized noble metal utilization.