Investigating Interfacial Coupling in Janus XP ₃ -Based 2D Heterostructures for Photocatalytic Redox Processes

High Resolution Image Download MS PowerPoint Slide Understanding and controlling interfacial electronic coupling in two-dimensional (2D) heterostructures is essential for designing materials with suitable band-edge alignment, efficient charge separation, and enhanced photocatalytic redox activity. Here, we investigate vertical heterobilayers constructed from two distinct XP 3 monolayers (X = Ge, Sb, Bi, Sn, Al, Ga, and Pb) using first-principles density functional theory. The resulting Janus heterobilayers are energetically favorable and elastically stable, with electronic band gaps ranging from metallic and near-metallic to semiconducting regimes. The interfacial coupling is discussed in terms of physically motivated descriptor-based trends, including metal–metal interlayer distance, vertical interlayer separation, electron localization at the midpoint of the interfacial metal–metal contact, Bader charge redistribution, and integrated crystal orbital Hamilton population (ICOHP)-derived bonding contributions. To rationalize these effects, we identify distinct coupling regimes spanning van der Waals (vdW)-dominated, intermediate hybridized, and partially covalent interfacial regimes. Optical absorption calculations indicate visible-to-near-infrared activity in selected systems, and band-edge alignment identifies potential candidates for selective redox processes. This work provides a physically grounded understanding of interfacial coupling in XP 3 heterostructures and offers practical guidelines for tuning their electronic structure, charge separation behavior, and redox functionality within this material family.