Basal and edge plane activity of two-dimensional Dirac semimetal NiTe₂ for hydrogen evolution reaction

Nickel ditelluride (NiTe₂), one of the group-10 transition metal dichalcogenides, has shown intriguing surface states originating from its topological semimetallicity. Here, we demonstrate abnormal catalytic activities at the NiTe₂ surface for the hydrogen evolution reaction (HER). We investigate the differences in catalytic activities at the basal and edge planes of NiTe₂ using a micro-sized electrochemical reactor. The basal plane is found to be more active than the edge plane, resulting in a current density at the basal plane of NiTe₂ exceeding 700 mA/cm² with a small overpotential of −0.162 V. Interestingly, our ab initio calculations show a discrepancy with the experimental measurements, indicating that the crystal-orientation-dependent HER activity highlights the unique characteristics of a topological semimetal, which can significantly influence the HER in NiTe₂ catalysts.