Electrocatalytic Hydrogen Evolution on SiX Nanosheets: Unlocking Superior Activity through Cu Single-Atom Decoration

Non-noble-metal-decorated two-dimensional (2D) materials, used as single-atom catalysts (SACs), are the most favorable for catalytic activities due to their low cost and high efficiencies. Herein, we investigated single Cu/Co-atom-decorated SiX (X = group V) compounds for the hydrogen evolution reaction (HER) using first-principles calculations. The Cu/Co decoration on SiX nanosheets significantly changes the surface charge distribution as well as its electronic properties. As a consequence, semiconductor-to-metal phase transition is observed, leading to a higher electrical conductivity and thus benefiting the HER activity. Under acidic conditions, except for Cu@SiN, all other Cu@SiX SACs exhibit good catalytic activities with Gibbs free energy (ΔGHER) very close to zero. The best HER activity is exhibited by Cu@SiBi, indicating an ultra-low ΔGHER of −0.002 eV. The Cu decoration enhances the HER activity of pristine SiX (X = As, Sb, Bi) by 95−98%, whereas Co decoration makes them inert. The Cu@SiX and Co@SiX SACs are found to exhibit enhanced HER activity relative to pristine SiX compounds. Our results confirm that Cu decoration is an effective strategy to improve the electrocatalytic activity and will pave the way forward in designing highly efficient SACs.