High-Performance Hydrogen Evolution Reaction Catalysts in Two-Dimensional Nodal Line Semimetals

The discipline of topological quantum catalysts (TQCs) is developing due to the emergence of exotic quantum materials and their corresponding catalysts. Although a series of 3D TQCs with different topological signatures are proposed, the emergence of 2D TQCs in 2D topological semimetals is still rarely touched by others. As a typical example, we proposed that the 2D nodal line semimetal Cu₂Si monolayer is a superior TQC for hydrogen evolution reaction (HER). Using first-principles calculations, we find that the Cu₂Si monolayer exhibits two Γ-centered nodal lines (L₁ and L₂) in the k_z = 0 plane. The Gibbs free energy (ΔG_H*) of Cu₂Si is as low as 0.195 eV, comparable to that of Pt, and better than other conventional catalysts. Moreover, it is found that changing the position of nodal lines (relative to the Fermi level) under different electron/hole conditions can effectively affect the catalytic activity of HER. Besides Cu₂Si, the emergence of high HER performance in other 2D nodal line semimetals, Ti₃C₂, Cr₂S₃, ScCl, and CuSe, is also theoretically determined. These results highlight the critical role of nodal lines in studying electrocatalytic mechanisms for TQCs and benefit the seeking of high-performance HER catalysts without noble metals on a 2D scale.