Boosted photocatalytic water splitting over a direct Z-scheme CdTe/C2N van der Waals heterojunction: a first-principles insight into photocatalytic activity

Abstract

The quest for sustainable and clean energy sources has led to significant research into photocatalytic water splitting, a process that converts solar energy into hydrogen fuel. This study demonstrates constructing a high-performance CdTe/C₂N van der Waals heterojunction for solar-driven water splitting hydrogen evolution. The proposed CdTe/C₂N heterojunction, investigated using first-principles calculations, integrates favorable structural stability and features a direct bandgap of 1.51 eV. The separation of photogenerated carriers is effectively facilitated by the built-in electric field oriented from CdTe to C₂N. The Gibbs free energy change (ΔG) for the hydrogen evolution reaction (HER) is found to be −0.11 eV, which is significantly closer to zero than that of the individual monolayers, thereby enabling near-ideal reaction kinetics. For the oxygen evolution reaction (OER), sufficient potential is provided by photogenerated holes in C₂N under illumination to overcome the energy barrier, ensuring spontaneous water splitting. Additionally, the enhanced visible light absorption, elevated electron mobility, and suppressed high energy carrier recombination via the Z-scheme mechanism make the heterojunction achieve a solar-to-hydrogen (STH) conversion efficiency of 10.04%, surpassing the industrial threshold of 10%. Therefore, this work presents a promising approach to achieving clean energy technologies through advanced photocatalysts.