Hydrogen Embrittlement as a Conspicuous Material Challenge - Comprehensive Review and Future Directions

Hydrogen is considered a clean and efficient energy carrier crucial for shapingthe net-zero future. Large-scale production, transportation, storage, and use of greenhydrogen are expected to be undertaken in the coming decades. As the smallest element inthe universe, however, hydrogen can adsorb on, diffuse into, and interact with many metallicmaterials, degrading their mechanical properties. This multifaceted phenomenon isgenerically categorized as hydrogen embrittlement (HE). HE is one of the most complexmaterial problems that arises as an outcome of the intricate interplay across specific spatialand temporal scales between the mechanical driving force and the material resistancefingerprinted by the microstructures and subsequently weakened by the presence of hydrogen. Based on recent developments in thefield as well as our collective understanding, this Review is devoted to treating HE as a whole and providing a constructive andsystematic discussion on hydrogen entry, diffusion, trapping, hydrogen−microstructure interaction mechanisms, and consequencesof HE in steels, nickel alloys, and aluminum alloys used for energy transport and storage. HE in emerging material systems, such ashigh entropy alloys and additively manufactured materials, is also discussed. Priority has been particularly given to these lessunderstood aspects. Combining perspectives of materials chemistry, materials science, mechanics, and artificial intelligence, thisReview aspires to present a comprehensive and impartial viewpoint on the existing knowledge and conclude with our forecasts ofvarious paths forward meant to fuel the exploration of future research regarding hydrogen-induced material challenges.