Computational Screening of Single-Atom Catalysts on Two-dimensional SiP₃ Monolayer for HER, OER, and ORR

Single-atom catalysts (SACs), constructed by immobilizing transition-metal (TM) atoms on two-dimensional (2D) supports, have attracted widespread interest due to their exceptional atomic efficiency and tunable coordination environments. Nevertheless, current research predominantly focuses on carbon-based materials, with studies on alternative substrate types remaining relatively limited. Herein, we employ first-principles calculations to systematically assess the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) activities of SACs (TM@SiP₃), which are constructed by anchoring TM atoms onto a 2D SiP₃ monolayer. Among all the stable configurations, Ni@SiP₃ exhibits outstanding HER activity, characterized by a very low hydrogen adsorption free energy (ΔG_H*) of 0.05 eV. Meanwhile, Rh@SiP₃ demonstrates the highest OER activity with an ultralow overpotential (η) of 0.46 V, along with an ORR overpotential of 0.71 V, identifying it as an excellent bifunctional catalyst. Additionally, Pt@SiP₃ also shows promising bifunctional activity for both HER (ΔG_H* = 0.10 eV) and ORR (η^ORR = 0.61 V). This study expands the design paradigm for multifunctional electrocatalysts and provides valuable insights into the exploration of SACs based on 2D non-carbon substrates.