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

Facilitating active NiOOH formation via Mo doping towards high-efficiency oxygen evolution

“…Considering the natural abundance of 18 O, the minimum detectable amount of 34 O 2 during the OER is about 0.4%. 65 The DEMS results suggest that the NiFe-LDH and NiFeMo-2 electrocatalysts mainly follow the adsorbate evolution mechanism (AEM) pathway. The tetramethylammonium cation (TMA + ) has a strong binding ability with the O 2 2− intermediate species, thus prohibiting the LOM pathway of the OER.…”

Mapping current high-entropy materials for water electrolysis: from noble metal to transition metal

“…Very recently, the ultrafine sub-2 nm IrRuNiMoCo high-entropy alloy nanoparticles with Ir-rich IrRuNiMo medium-entropy oxide shell (Ir-MEO) and a IrRuCoNiMo HEA core (HEA@Ir-MEO NPs) were prepared by wet-chemical reduction and subsequent galvanic replacement. 118 As a catalyst for acidic OER, outstanding activity was observed with an overpotential of 243 mV at 10 mA cm −2 and a mass activity of 261.5 A g Ir −1 . For practical application in proton-exchange membrane water electrolysis, the optimized catalyst delivers excellent performance (1.85 V/3.0 A cm −2 @80 °C), long-term stability (>500 h@1.0 A cm −2 ), and low energy consumption (3.98 kW h N −1 m −3 H 2 @1.0 A cm −2 ).…”