Shaping Sustainable Green Hydrogen Generation with High-Entropy Alloy Catalysts: A Review and Future Perspectives

Green hydrogen is set to become a leading player in global energy transformation. Over the past few years, there has been an increasing trend of interest in “green hydrogen”, hydrogen produced from renewable energy sources. Green hydrogen production employing renewable sources to energize the electrolysis of water is one of the main avenues in the economy’s decarbonization and the battle against climate change because it can be employed in a range of industries without producing any greenhouse gases. The quantity of the produced hydrogen and electricity relies on the longevity of the electrode composed of electrocatalyst/photocatalyst types. With this in view, high-entropy alloys (HEAs) have some benefits as electrocatalysts and photocatalysts for the production of green hydrogen because of their special multielemental constitution and structural properties. Their high configurational entropy stabilizes single-phase solid solutions that have excellent thermal and chemical stability under severe reaction conditions. High-entropy alloys (HEAs) as efficient electrocatalysts/photocatalysts with their unique multielemental compositions and tunable electronic structures have generated interest in the past as efficient catalysts for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). This review examines the synthesis methods of HEA-based catalysts through mechanical alloying (MA), sol–gel, solvothermal, electrodeposition, and microwave-assisted synthesis methods. We also offer insights into the theoretical understanding of catalytic activity, with a focus on density functional theory (DFT) calculations to elucidate electronic structure, adsorption energies, and reaction pathways. HER and OER processes are deeply discussed with emphasis placed on how HEAs enhance reaction kinetics, charge transfer, and stability. Through the integration of experimental and computational perspectives, this review aims to better comprehend HEA-based electrocatalysis and photocatalysis and to pave the way for their future application in green hydrogen production.