Multi-site synergistic hydrogen evolution reactions on porous homogeneous FeCoNiCu high-entropy alloys fabricated by solution combustion synthesis and hydrogen reduction

A combination process of solution combustion synthesis and hydrogen reduction was proposed to prepare porous homogeneous FeCoNiCu high-entropy alloys (HEAs) for hydrogen evolution reaction (HER). Solution combustion synthesis was herein employed to obtain the multiple composite oxide precursor with tunable molar ratio of elements and pore structure, as well as uniform element distribution. The generated bulk porous HEAs composed of single-phase solid solution were achieved by hydrogen reduction of the oxide precursor at optimal temperature. The porous structure and specific surface area of oxide precursor and reduced HEA could be adjusted by varying the mass ratio of metal nitrates to glycine and the reduction temperature. The prepared FeCoNiCu0.5 HEA with enriched porosity and high specific surface area showed high catalytic activity and excellent electrochemical stability during alkaline HER. Density functional theory (DFT) calculation revealed the electronic interaction between Fe, Co, Ni and Cu elements facilitated the efficiency for H* adsorption and H2 desorption, and enhanced the catalytic activity of the Co/Ni sites. This work provided an approach to develop porous high-entropy alloy catalysts for HER and other applications.