Density Functional Theory Study of Phosphorus Silicide Monolayers as Anodes for Lithium-Ion Batteries and Electrocatalysts for CO₂ Reduction

Using particle swarm optimization methodology for crystal structure prediction and first-principles density functional theory, we predicted a phosphorus silicide (PSi) monolayer that meets the thermodynamical, dynamical, and mechanical stability requirements. The PSi monolayer possesses a graphene-like honeycombed structure with a small puckering corresponding to a distance, d, of 0.939 Å and is metallic under the PBE or HSE06 functional. Based on the metallic property, we first found that the PSi monolayer can be used as the anode of a lithium-ion battery with a barrier energy of 0.65 eV and a theoretical capacity of 306.3 mA g h–1, for which the puckering structure influences the diffusion of Li ions on the surface of the PSi monolayer. We further studied the adsorption behavior of CO2, and the Si site in the PSi monolayer has unexpected activity toward adsorption and activation of CO2, showing that the PSi monolayer exhibits superior catalytic performance for the CO2 reduction reaction (CO2RR) to CH4 with the optimal path of CO2RR as CO2 → *COOH → *CO → *COH → *CHOH → *CH → *CH2 → *CH3 → *CH4. This work demonstrates great potential applications of the PSi monolayer on the energy storage battery and low-cost electrocatalytic materials for the efficient separation and conversion of CO2, respectively.