Sub‐2 nm IrRuNiMoCo High‐Entropy Alloy with Iridium‐Rich Medium‐Entropy Oxide Shell to Boost Acidic Oxygen Evolution

Abstract

Ensuring high catalytic activity and durability at low Ir usage is still a big challenge for the development of electrocatalysts towards oxygen evolution reaction (OER) in proton exchange membrane water electrolysis (PEMWE). Here, a rapid liquid‐reduction combined with surface galvanic replacement strategy is reported to synthesize the sub 2 nm high‐entropy alloy (HEA) nanoparticles featured with Ir‐rich IrRuNiMo medium‐entropy oxide shell (Ir‐MEO) and a IrRuCoNiMo HEA core (HEA@Ir‐MEO), which exhibits a low overpotential of 243 mV at 10 mA cm−2 and high mass activity (261.5 A gIr−1). Advanced spectroscopies reveal that the Ir‐rich MEO shell inhibits the severe structural evolution of transition metals upon the OER, thus guaranteeing the structural stability. In‐situ DEMS, activation energy analysis and DFT calculations unveil that the OER on HEA@Ir‐MEO follows an adsorbate evolution mechanism pathway, where the energy barrier of rate‐determining step is substantially lowered, interpreting the enhanced OER kinetics. The optimized catalyst is assembled into PEM electrolyzer with low Ir usage of ca. 0.4 mg cm−2, and to give the excellent performance (1.85 V/3.0 A cm−2 °C), long‐term stability (>500 h@1.0 Acm−2) and low energy consumption (3.98 kWh Nm−3 H2 @1.0 A cm−2), realizing the dramatical reduction of hydrogen production cost to USD 0.88 per kg H2.This article is protected by copyright. All rights reserved