Unravelling the effects of surface functional groups on hydrogen adsorption inside multilayered Ti2CTx MXene

Solid-state hydrogen storage has become a key focus in hydrogen storage technology research. Multilayered MXenes are a highly attractive candidate for hydrogen storage applications. In this study, the effects of surface functional groups, including –F, –OH, and =O, on hydrogen adsorption in multilayered Ti 2 CT x MXene are investigated using first principle calculations . The addition of these functional groups can weaken the hydrogen adsorption in the multilayered Ti 2 CT 2 MXene . It is found that OH-terminated MXene is thermodynamically unfavorable for hydrogen adsorption. Moreover, the multilayered Ti 2 CT x MXene with partially occupied functional groups exhibits superior hydrogen adsorption. Specifically, the MXene with 89 % of =O groups strongly adsorbs hydrogen molecules (−0.16 eV/H 2 ), indicative of a strong physisorption . This strong adsorption is attributed to the relatively large orbital overlap, as analyzed by the projected density of states (PDOS). Additionally, a specific configuration of the electrostatic field, formed by functional groups and MXene surface atoms, enhances the overall hydrogen adsorption. This study elucidates the effects of functional groups on hydrogen adsorption in multilayered Ti 2 CT x MXene and provides guidance for other candidates of MXenes' family, addressing the crucial needs in hydrogen storage applications.