Palladium-decorated SiX (X = N, P, As, Sb, Bi) catalysts for hydrogen evolution

Abstract

Developing single atom catalysts (SAC) is a promising and useful strategy for designing highly efficient and low-cost photo- or electrocatalysts that are active towards hydrogen evolution reaction (HER). Herein, we have explored the structural, electronic and HER catalytic activity of Pd-decorated SiX (X = N, P, As, Sb and Bi) SACs using density-functional theory calculations. A strong interaction exists between the Pd atom and SiX nanosheets which modifies the electronic properties which in turn increases the electrical conductivity. With the help of several descriptors, including the Gibbs free energy change, d-band center, COHP analysis and the exchange current density, we systematically investigated the HER activity of the Pd@SiX (X = group-V) SACs. It is observed that under zero external potential (U_e = 0) and at a pH of 0, the Gibbs free energy (ΔG_H*) of Pd@SiSb and Pd@SiBi reduces to 0.96 eV and 0.67 eV which is nearly a 40% and 61% reduction as compared to pristine SiSb (ΔG_H* = 1.60 eV) and SiBi (ΔG_H* = 1.72 eV), respectively. Additionally, under the effect of supplied external potentials, the ΔG_H* even reduces to 0.23 eV and −0.22 eV for the Pd@SiSb and Pd@SiBi SACs, respectively, with higher exchange current densities indicating a better HER performance. Hence we propose that, from the family of SiX (X = group-V) binary compounds, the Pd@SiSb and Pd@SiBi SACs are suitable electrocatalysts for the HER. We strongly believe that our findings will shed some light on the effective utilization of noble elements like palladium for the effective design of SACs.