DFT screening of single atom catalysts in van der Waals gap of Ti3C2Tx MXenes for enhanced hydrogen evolution reaction

Abstract

Single-atom catalysts (SACs) on MXene surfaces are extensively studied for various electrochemical reactions. The impact of van der Waals (vdW) interactions, however, on such catalysts’ activity has not been systematically explored through a high throughput screening. The current study uses the vdW interactions in a double-layer Ti₃C₂T_x MXene to improve the hydrogen evolution reaction (HER). In this venue, the density functional theory (DFT + D3) was applied to study double-layer MXenes supported 3d, 4d, and 5d transition metals, labeled as M_vdW@Ti₃C₂T_x. The goal was to identify SACs with appropriate electrochemical and thermodynamic stability and low HER overpotentials. It was discovered that, the HER may occur within the vdW gap of Tc_vdW@Ti₃C₂T_x and Re_vdW@Ti₃C₂T_x, resulting in overpotentials of 0.06 and 0.03 V, respectively. The improved HER activity was attributed to the charge density present in the corresponding vdW gaps. Density of states (DOS) analysis showed the hybridization of the d_yz orbital of active sites with the s orbital of the H∗ intermediate through the HER. This work is of great importance in the discovery and design of multi-layer electrocatalysts, making vdW interactions an effective tool in electrochemistry at room temperature.