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Published on: December 6, 2021
Structural reorganization of high-entropy alloy CoNiCuMoZn for enhanced hydrogen evolution performance
Huihua Niu1, Jiongliang Yuan1, Yuning Su1
1College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029, PR China.
None:
High-entropy alloy (HEA) catalysts have great potential for hydrogen production in electrocatalytic water splitting, which is superior to conventional Pt/C catalysts. In this work, the noble-metal-free HEA CoNiCuMoZn was fabricated by pulsed electrodeposition, and its structural reorganization was carried out by cyclic voltammetry. The reconstituted HEA, R-CoNiCuMoZn, was changed to spherical particles with many wrinkles on the surface. Co, Ni, Mo, and Zn in R-CoNiCuMoZn exhibited an elevated electron cloud density, thus promoting the generation of absorbed hydrogen (Hads), which benefited hydrogen evolution reaction (HER). The electron paramagnetic resonance (EPR) results showed that Mo vacancies increased after structural reorganization, which was the main reason for the enhanced hydrogen evolution performance. The addition of the metal Zn with weak Hads binding affinity accelerates the Heyrovsky step. The R-CoNiCuMoZn catalyst achieved an ultra-low overpotential of only 43.0 ± 0.3 mV in 1.0 M KOH solution at the current density of 400 mA cm-2, and it exhibited a Tafel slope of 21.20 mV dec-1. After a stability test of 50 h, there was no significant decay in current density. Density functional theory (DFT) calculation reveals that Mo vacancies reduce the dissociation energy barrier, and metal Zn reduces the Helovsky step activation energy. This study provides a new approach for developing high-efficiency HER electrocatalysts.
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