Enhanced HER Performance of Amorphous/Crystalline Ni Nanoparticles-Decorated Maze-like Nanoporous High-Entropy Alloy.

Nanoporous high-entropy alloys (HEAs) are emerging as promising electrocatalysts due to their distinctive properties. Surface engineering is an efficient strategy for the further advancement of hydrogen evolution reaction (HER) electrocatalysts. Herein, a maze-like nanoporous CoCrFeNiAl HEA (NPCCF) with fine ligament sizes of ∼17 nm was fabricated using a selective phase dealloying strategy. Compared with commercial thick-ligament porous nickel foam (NF) and as-spun CoCrFeNiAl ribbon, NPCCF, with its nanoscale ligament 3D porosity, possesses a larger electrochemical surface area and exhibits better HER performance. Afterwards, Ni amorphous/crystalline nanoparticles (Ni NPs) with diameters of ∼100 nm were decorated on the NPCCF via a facile electrodeposition method, resulting in a composite electrocatalyst (NPCCF@Ni) designed to boost the HER process. Electrochemical measurements showed that NPCCF@Ni exhibited a low overpotential of 50 mV at a current density of 10 mA cm for HER in 1.0 M KOH. The excellent catalytic activity is attributed to the large active surface area and fast electron transfer ability of the maze-like 3D nanoporous structure decorated with Ni NPs. Theoretical calculations demonstrated that the Ni atoms modified on the CoCrFe model provided a synergistic effect, altering the electronic structure to optimize the adsorption/desorption energy of adsorbed hydrogen (H*) and reduce the reaction energy barrier of the HER process, resulting in lower Gibbs free energy (Δ). This work explores the advantages of nanoporous HEAs as electrocatalysts and provides insights into the design of HER catalysts with excellent performance through surface modification strategies.