Angle-dependent electrocatalytic activity of twisted bilayer graphene for the hydrogen evolution reaction

Two-dimensional (2D) materials are attractive for their unique electronic structures and electrocatalytic properties. In this work, we propose to use the twist angle as a knob to tune the electrocatalytic properties of 2D materials. As proof of concept, we investigate the effects of twist angle (>10°) on the electrocatalytic properties of twisted bilayer graphene (tBLG). We predict the activity of tBLG with the twist angle of 13.174° and 21.787° for the hydrogen evolution reaction (HER) using a density functional theory (DFT) calculation and computational hydrogen electrode (CHE) approach. We calculate the hydrogen adsorption energy (ΔG_H*) at various sites on tBLG and examine their angle-dependency. By comparing the ΔG_H* for different active sites of untwisted bilayer graphene (BLG) and tBLG, we find that the ΔG_H* decreases with the increase of the twist angle. As a result, the thermodynamic limiting potential for the HER increases with the twist angle. Furthermore, the ΔG_H* shows a correlation with the layer distance (d̄) and the site location on the 2D plane. Detailed analysis reveals that the twist of bilayer graphene could increase the z height (d_z) of the active sites as a function of their distance to the symmetry centers, alter the local geometry of the active sites, and therefore modify the ΔG_H*. These results indicate that the twist angle can be effectively used as a knob to fine-tune the electrocatalytic properties of 2D materials.