High-entropy alloys for accessing hydrogen economy via sustainable production of fuels and direct application in fuel cells

Heavy consumption of fossil fuels has raised concerns over the climate change and energy security in the past decades. In this review, hydrogen economy, as a clean and sustainable energy system, is receiving great attention. The success of future hydrogen economy strongly depends on the storage of renewable energy in hydrogen and hydrogen-rich chemicals through electrolyzers and conversion back to electricity via fuel cells. Electrocatalysts are at the heart of these critical technologies and great efforts have been devoted to preparing highly efficient nanomaterials. High-entropy alloys (HEAs), with their unique structural characteristics and intrinsic properties, have evolved to be one of the most popular catalysts for energy-related applications, especially those associated with hydrogen economy. Herein, recent advances regarding HEAs-based hydrogen economy are comprehensively reviewed. Attention is paid to the discussion of emerged HEAs as a new class of materials in hydrogen energy cycle, carbon-based hydrogen energy cycle, and nitrogen-based hydrogen energy cycle, covering the sustainable electrochemical synthesis of hydrogen and hydrogen-rich fuels and their direct application in fuel cells. Based on this overview, the challenges and promising directions are proposed to guide the development of HEAs research, aiming to achieve significant progress for further accessing hydrogen economy.