First principles calculations investigation of optoelectronic properties and photocatalytic CO2 reduction of (MoSi2N4)5-n/(MoSiGeN4)n in-plane heterostructures

In-plane (MoSi2N4)5-n/(MoSiGeN4)n heterostructures have been delicately designed and systematically studied using first-principles density functional theory calculations. Such heterostructures exhibit dynamical stability as verified by calculated phonon dispersion spectra. The calculated band gap values increase with the MoSi2N4 area increase, as 1.385(1.860) eV for (MoSi2N4)0/(MoSiGeN4)5 and 1.925(2.385) eV for (MoSi2N4)5/(MoSiGeN4)0 using PBE (HSE06). By density of states analysis, the Ge 4p state made an excellent contribution to moving up the conduction band position and altering the band gap value. Also, the work function values can be modulated by the n numbers of (MoSi2N4)5-n/(MoSiGeN4)n. Based on optical and redox potential calculations, the calculated results suggest that the (MoSi2N4)5-n/(MoSiGeN4)n heterostructures have the potentials to be applied as ideal photocatalysts for photocatalytic CO2 reduction. Notably, different photocatalytic reduction reaction products can be formed using such (MoSi2N4)5-n/(MoSiGeN4)n in-plane heterostructures with different n values, indicating that selective catalytic reduction reactions can be realized on the in-plane heterostructures. Our findings suggest that (MoSi2N4)5-n/(MoSiGeN4)n monolayer in-plane heterostructures can serve as a new class of 2D materials for photovoltaic and photocatalysis applications, providing insightful guidance for the development of optoelectronic devices.