Mechanisms of hydrogen embrittlement, mitigation strategies, and emerging materials for hydrogen energy and advanced...

Hydrogen is considered one of the most promising energy carriers for low-carbon energy systems. However, hydrogen embrittlement (HE) poses a threat to the structural integrity and long-term reliability of metallic materials used in hydrogen production, storage, transportation, and utilization. Microstructural features such as dislocations, vacancies, grain boundaries, precipitates, and phase interfaces can act as hydrogen trapping sites. Hydrogen atoms introduced through gaseous exposure, electrochemical reactions, or corrosion processes can accumulate at these sites. Consequently, hydrogen-metal interactions can reduce ductility, accelerate crack initiation and propagation, and promote premature failure under static and cyclic loading conditions. This brief overview discusses the recent advances in hydrogen uptake, diffusion, trapping, and damage mechanisms, including hydrogen-enhanced decohesion (HEDE), hydrogen-enhanced localized plasticity (HELP), and hydrogen-enhanced strain-induced vacancy formation (HESIV). HE susceptibility is examined in relation to alloy chemistry, microstructure, environmental factors, and mechanical loading conditions. In addition, recent advances in multiscale modelling, in situ and operando characterization techniques, artificial intelligence (AI)-assisted prediction, and hydrogen detection methodologies are discussed. Moreover, mitigation strategies involving microstructure optimization, surface engineering, protective coatings, heat treatment of materials, and stress management are investigated. This review compares and contrasts promising emerging materials for hydrogen energy and advanced manufacturing, such as high-entropy alloys, additively manufactured alloys, and advanced high-strength steels, in contrast to other reviews that primarily focus on specific alloy types or HE mechanisms. Finally, future research priorities are identified, including standardized evaluation procedures, testing under real-world service conditions, data standardization, model validation, and the development of safe, durable, hydrogen-compatible metallic materials.