FeP₂ monolayer: isoelectronic analogue of MoS₂ with excellent electronic and optical properties

Two-dimensional semiconductors with suitable indirect band gaps, excellent light absorption capacity, and oxidation resistance are particularly suitable for material applications. Here based on first-principle calculations, we report that the FeP₂ monolayer, which is isoelectronic with MoS₂, has novel electronic properties and an ultra-low diffusion energy barrier of K on the surface, indicating its potential as an anode material of K-ion batteries. The calculated phonon dispersion curves, molecular dynamics, and elastic constants showed that it has high structural stability and oxidation resistance. The monolayer was a semiconductor with an indirect band gap of 0.68 eV. In addition, the FeP₂ monolayer had obvious light absorption in the infrared, visible, and ultraviolet regions, which can be widely used in optoelectronic devices. Bonding analysis showed that there were multicenter bonds inside every hexagonal ring. As the anode material of K-ion batteries, the FeP₂ monolayer had a capacity of 456.84 mA h g^-1, low diffusion energy barrier, and open-circuit voltage. All these characteristics suggest that the FeP₂ monolayer is a potential anode material for K-ion batteries, which needs to be further verified by experiments.