MXene as a hydrogen storage material? A review from fundamentals to practical applications

Hydrogen is rapidly emerging as a leading candidate for the transition from conventional non-renewable energy sources to sustainable alternatives, owing to its remarkably high energy density. The economic viability of hydrogen storage is a significant challenge, as conventional storage methods, such as compression, or liquefaction, require complex infrastructure. On the other hand, solid-state hydrogen storage involving physisorption or chemisorption requires sophisticated system design due to extremely low or high reaction enthalpy. In this scenario, scientists are focusing on materials capable of capturing hydrogen under nearly ambient conditions with moderate binding energies to facilitate thermoneutral reactions. While MXenes, two-dimensional transition metal carbides/nitrides, hold significant potential in this area, their application in hydrogen storage has not been extensively explored and is yet to be fully realized. Despite numerous theoretical studies investigating the mechanism of hydrogen adsorption on MXenes, limited experimental reports have focused on the standalone use of MXenes as a storage material, primarily due to real-life application challenges and uncertainties stemming from existing theoretical inconsistencies. Existing reviews on MXenes and hydrogen storage lack in-depth analysis of theoretical and experimental disparities. Our comprehensive review aims to bridge these gaps for further research advancement.