Understanding mechanism conversion in hydrogen evolution reaction on PtSe 2: Role of layer number explored by density functional theory

The emerging two-dimensional (2D) transition metal dichalcogenide PtSe 2 is a promising catalyst for hydrogen evolution reactions (HER). In this study, we performed density functional theory (DFT) calculations to investigate the mechanism conversion of the HER over PtSe 2 with respect to the changes in the number of layers of the catalyst. We found that the adsorption energy of hydrogen ( Delta G H ) changed with an increase in the number of 2D material layers, and the most significant change occurred when the number of layers was increased from one to two. Furthermore, we conducted dynamic calculations to reveal the mechanisms of the HER on the basal and V se surfaces. Owing to the changes in Delta G H , the HER mechanism undergoes a conversion between Volmer - Heyrovsky and Volmer - Volmer '- Tafel mechanisms. Through frontier orbitals analysis, layer-stacking altered the bonding capability between hydrogen and PtSe 2 surfaces by altering the electronic structure of the PtSe 2 surface. This study demonstrates the synergistic effect of interlayer interactions on the HER over PtSe 2 catalysts and can be helpful in stimulating innovative ideas for 2D material design.