STRUCTURAL AND PHASE FACTORS DETERMINING THE HYDROGEN SORPTION PROPERTIES OF HIGH-ENTROPY ALLOYS

Abstract

Hydrogen is considered one of the most promising energy carriers for the development of sustainable energy systems, which has stimulated growing interest in advanced materials for efficient and safe solid-state hydrogen storage. High-entropy alloys have attracted considerable attention because of their unique compositional complexity, phase stability, and the possibility of tailoring their hydrogen sorption behavior through microstructural and phase engineering. This review aims to analyze the structural and phase factors determining the hydrogen sorption properties of high-entropy alloys and to evaluate the influence of synthesis methods on their microstructure and hydrogen storage performance. The study is based on a comprehensive analysis and critical assessment of recent scientific publications concerning the interaction of hydrogen with high-entropy alloys, the effects of phase composition, crystal structure, elemental distribution, lattice distortion, and microstructural characteristics on hydrogen absorption and desorption processes. Particular attention is paid to the influence of fabrication routes, including arc melting, mechanical alloying, and spark plasma sintering, on phase formation, grain refinement, chemical homogeneity, and defect structure, which directly affect hydrogen storage capacity, sorption kinetics, activation behavior, reversibility, and cycling stability. The review integrates current knowledge on the relationships between processing conditions, structural evolution, and hydrogen sorption characteristics, providing a comprehensive understanding of the factors governing the performance of high-entropy alloys. The presented analysis may serve as a scientific basis for the development and optimization of high-performance hydrogen storage materials for future hydrogen energy applications.