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^-2 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<i>G</i>_<i>H</i>_*). 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.