A Novel Two-Dimensional ZnSiP₂ Monolayer as an Anode Material for K-Ion Batteries and NO₂ Gas Sensing

Using the crystal-structure search technique and first-principles calculation, we report a new two-dimensional semiconductor, ZnSiP₂, which was found to be stable by phonon, molecular-dynamic, and elastic-moduli simulations. ZnSiP₂ has an indirect band gap of 1.79 eV and exhibits an anisotropic character mechanically. Here, we investigated the ZnSiP₂ monolayer as an anode material for K-ion batteries and gas sensing for the adsorption of CO, CO₂, SO₂, NO, NO₂, and NH₃ gas molecules. Our calculations show that the ZnSiP₂ monolayer possesses a theoretical capacity of 517 mAh/g for K ions and an ultralow diffusion barrier of 0.12 eV. Importantly, the ZnSiP₂ monolayer exhibits metallic behavior after the adsorption of the K-atom layer, which provides better conductivity in a period of the battery cycle. In addition, the results show that the ZnSiP₂ monolayer is highly sensitive and selective to NO₂ gas molecules.