Built–in electric field and atomic–level interfacial channels synergistically drive Type–I to Type–II transition and directed carrier separation in 2D/2D CeO2/SnSe heterojunction

Photocatalytic water splitting for hydrogen production is a key approach to addressing the energy crisis. However, Type-I heterojunctions are limited by issues such as low photogenerated carrier separation efficiency, weak intrinsic electric fields at the interface, and a scarcity of active sites on the surface. To address these issues, this study proposes a synergistic strategy combining “interface electric field engineering” and “surface molecular engineering”: A 2D/2D CeO 2 /SnSe heterojunction is first constructed via a stepwise hydrothermal method. Subsequently, ammonium hexachlorostannate(IV) ([SnCl 6 ] 2- ) is introduced onto the heterojunction surface via electrostatic adsorption. After subsequent drying, these complexes undergo conversion to form Sn-O-Ce bonds at the interface, achieving “molecular welding” and enhancing interfacial coupling. Kelvin probe force microscopy (KPFM) and electron paramagnetic resonance (EPR) measurements confirm the successful establishment of the built-in interfacial electric field. Density functional theory (DFT) calculations further reveal that this built-in electric field drives photogenerated electrons from SnSe across the interface and into the more negative conduction band of CeO 2 , enabling the composite material, which originally exhibited Type-I band alignment, to achieve a Type-II-like charge separation pathway under illumination. Photocatalytic hydrogen evolution tests indicate that the hydrogen evolution rate of the optimized material has increased twenty-fold. This work provides both experimental and theoretical grounds for the regulation of the band structure of heterojunctions through interfacial chemical engineering, as well as for the development of highly efficient photocatalysts. Download: Download high-res image (186KB) Download: Download full-size image