Plasma-regulated two-dimensional high entropy oxide arrays for synergistic hydrogen evolution: From theoretical prediction to electrocatalytic applications

In this work, we firstly predict through density function theory (DFT) that plasma-regulated 2D high entropy materials can show optimized hydrogen adsorption free energy (ΔGH) for promoting hydrogen evolution reaction (HER). Consequently, 2D high entropy FeNiCoMnVOx oxide arrays are fabricated, and further treated by Ar plasma to generate oxygen vacancies on the surface of catalyst, which possess a well-defined crystal structure that are analogous to the structures of Mn3O4 and the morphology like a number of vertically aligned nanosheets. Remarkably, the catalyst exhibits superior electrocatalytic HER activity with a small overpotential of 81 mV to achieve the current density of 10 mA cm−2 and a Tafel slope of 88 mV dec−1. It can stably operate at 10 mA cm−2 up to 100 h with negligible activity decay. Further combination of experimental results and DFT computations illustrate the synergistic effect of five metal active sites that can dwindle the Gibbs energy barrier of the H* desorption step during the process of HER. In addition, oxygen vacancies which generated by Ar plasma can modulate the surface of catalyst to enrich the electron density of metal sites and contribute superior HER performance.