Amorphous High-Entropy Alloys as Innovative Materials for Hydrogen Energy: State of the Art and Development Prospects

Amorphous high-entropy alloys (AHEAs) represent a promising class of hydrogen energy materials, since they combine technically significant hydrogen capacity, fast sorption/desorption kinetics, and resistance to cyclic loading. These unique properties are caused by their complex chemical composition, which includes several hydride-forming elements, and the absence of a long-range order in their atomic structure, which creates favorable hydrogen diffusion conditions. This review systematizes current understanding of the fundamental properties of AHEAs. Special attention is paid to the structural features of amorphous alloys, the hydrogen distribution in their matrix, the influence of chemical composition on hydrogen capacity and structural stability, and the conditions for the formation of a thermodynamically stable amorphous state. The mechanisms of interaction between an amorphous structure and hydrogen and the kinetics of hydrogenation and dehydrogenation processes are considered separately. The principles of rational composition selection with allowance for the role of hydride-forming elements and thermodynamic parameters are discussed; they can be used to reveal the most promising multicomponent systems. AHEA synthesis methods, such as gas-phase technologies, melt quenching, and mechanochemical synthesis, are described in detail; modern approaches using plasma and additive technologies are also touched upon. The review covers modern approaches to theoretical modeling and machine learning (ML) for predicting the phase composition and hydrogen capacity of AHEAs, and attention is paid to promising directions in the development of hydrogen storage materials, where the integration of computer modeling, ML, and experimental investigations is considered to be the key to predicting the sorption properties of AHEAs and to selecting their compositions. In conclusion, the necessity of an interdisciplinary approach to integrate these materials into real hydrogen energy devices is emphasized.