Angle-Dependent Electrocatalytic Activity of Twisted Bilayer Graphene for Hydrogen Evolution Reaction

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