Drumhead surface states promoted hydrogen evolution reactions in type-II nodal-line topological catalyst Mg 3 Bi 2 .

An excellent catalyst generally meets three indicators: high electron mobility, high surface density of states and low Gibbs free energy (Δ G ) [H. Luo et al. Nat. Rev. Phys. , 2022, 4 , 611-624]. Recent studies have confirmed that topological materials exhibit more advantages than conventional precious metals with regard to the above-mentioned indicators. Herein, based on DFT calculations and symmetry analysis, we discovered for the first time that the topological surface states of Mg 3 Bi 2 with a Kagome lattice promote hydrogen evolution reactions (HERs). In particular, there exists a snake-like type-II nodal loop (NL), located on k z = 0 plane in Mg 3 Bi 2 . Besides, the NL forms a topologically protected drumhead surface state on the (001) surface. It was found that the Δ G (0.176 eV) value of the (001) surface is comparable to that of the precious metal Pt. Then, through hole doping and strain regulation, it was found that the catalytic activity of Mg 3 Bi 2 is closely related to the drumhead surface state formed by NL. With the above-mentioned results, this study not only provides a promising candidate material for hydrogen electrolysis, but also deepens our understanding of the dominant factors of NL semimetals for the catalytic activity.