Tailored electronic structure of Ir in high entropy alloy for highly active and durable bi-functional electrocatalyst for water splitting under acidic environment.

Abstract

Proton exchange membrane water electrolysis (PEMWE) requires an efficient and durable bi-functional electrocatalyst for HER and OER. Herein, we design Ir-based electrocatalyst using high entropy alloy (HEA) platform of ZnNiCoIrX with two elements (X: Fe and Mn). A facile dealloying in vacuum system enables the construction of nanoporous structure with high crystallinity using Zn as a sacrificial element. Especially, Mn incorporation into HEAs tailors the electronic structure of Ir site, resulting in the d-band center being far away from Fermi level. Downshift of the d-band center weakens the adsorption energy with reaction intermediates, which is beneficial for catalytic reactions. Despite low Ir content, ZnNiCoIrMn delivers only 50mV overpotential for HER at -50mA cm-2 and 237mV overpotential for OER at 10mA cm-2 . Furthermore, ZnNiCoIrMn shows almost constant voltage for HER and OER for 100h and high stability number of 3.4×105 nhydrogen nIr -1 and 2.4×105 noxygen nIr -1 , demonstrating exceptional durability of HEA platform. The compositional engineering of ZnNiCoIrMn limits the diffusion of elements by high entropy effects and simultaneously tailors electronic structure of active Ir sites, resulting in the modified cohesive and adsorption energies, all of which can suppress the dissolution of elements. This article is protected by copyright. All rights reserved.