Ru‐Doped Bimetallic Phosphide: A High‐Performance Air‐Breathing Electrode for Zn‐Air Batteries and an Efficient Electrocatalyst for Overall Water Splitting

ABSTRACT Zinc‐air batteries (ZABs) are promising next‐generation energy storage systems due to their high energy density and safety; however, their practical application is limited by sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics. Heteroatom‐doped transition metal phosphides offer strong potential as multifunctional electrocatalysts. Herein, we introduce a strategy to incorporate ruthenium (Ru) into bimetallic nickel cobalt phosphide (NiCoP), achieving efficient ORR, OER, and hydrogen evolution reaction (HER) performance. The Ru‐NiCoP@N‐doped carbon (NC) exhibits excellent bifunctional oxygen activity with an ultralow potential gap of 0.61 V. It displays remarkable HER activity with an overpotential of 36 mV at 10 mA cm −2 of current density in alkaline pH. The ZAB based on the Ru‐NiCoP@NC delivers a very high power density of 245 mW cm −2 , specific capacity of 790.4 mA h g Zn −1 , and energy density of 902.3 Wh kg Zn −1 . It shows an outstanding voltaic efficiency of 54.0% with negligible loss after 286 h. The water splitting cell employing Ru‐NiCoP@NC as both the cathode and anode exhibits an overall water splitting voltage of 1.45 V at 10 mA cm −2 , along with excellent durability. Density functional theory calculations elucidate the superior catalytic performance of Ru‐NiCoP@NC, driven by Ru‐induced charge redistribution that modulates adsorption–desorption kinetics and optimizes intermediate binding energies. This results in near‐ideal hydrogen adsorption for HER and significantly reduced energy barriers for ORR/OER.