Density Functional\nTheory Study of Phosphorus Silicide\nMonolayers as Anodes for Lithium-Ion Batteries and Electrocatalysts\nfor CO<sub>2</sub> Reduction

Using particle swarm optimization\nmethodology for crystal\nstructure\nprediction and first-principles density functional theory, we predicted\na phosphorus silicide (PSi) monolayer that meets the thermodynamical,\ndynamical, and mechanical stability requirements. The PSi monolayer\npossesses a graphene-like honeycombed structure with a small puckering\ncorresponding to a distance, <i>d</i>, of 0.939 Å and\nis metallic under the PBE or HSE06 functional. Based on the metallic\nproperty, we first found that the PSi monolayer can be used as the\nanode of a lithium-ion battery with a barrier energy of 0.65 eV and\na theoretical capacity of 306.3 mA g h<sup>–1</sup>, for which\nthe puckering structure influences the diffusion of Li ions on the\nsurface of the PSi monolayer. We further studied the adsorption behavior\nof CO<sub>2</sub>, and the Si site in the PSi monolayer has unexpected\nactivity toward adsorption and activation of CO<sub>2</sub>, showing\nthat the PSi monolayer exhibits superior catalytic performance for\nthe CO<sub>2</sub> reduction reaction (CO<sub>2</sub>RR) to CH<sub>4</sub> with the optimal path of CO<sub>2</sub>RR as CO<sub>2</sub> → *COOH → *CO → *COH → *CHOH →\n*CH → *CH<sub>2</sub> → *CH<sub>3</sub> → *CH<sub>4</sub>. This work demonstrates great potential applications of the\nPSi monolayer on the energy storage battery and low-cost electrocatalytic\nmaterials for the efficient separation and conversion of CO<sub>2</sub>, respectively.