HfS2/GeSe heterostructure engineering for superior photocatalytic hydrogen generation: design, mechanism, and efficiency

Abstract

In this study, HfS₂/GeSe heterostructures are constructed to address the issues of high carrier recombination and narrow light absorption in monolayer HfS₂ for photocatalysis. DFT and AIMD calculations reveal stacking-I as the most stable structure, in which electron transfer from HfS₂ to GeSe forms a 2.86 eV built-in electric field, enhancing photogenerated carrier separation. The HER and OER occur in the GeSe and HfS₂ layers, respectively, enabling overall water splitting. The heterojunction shows a high hole mobility (5148.61 cm² V⁻¹ S⁻¹ along the y-direction) and a theoretical STH efficiency of 24.63%. Gibbs free energy analysis indicates that the photogenerated carriers provide 0.39 eV (HER) and 0.62 eV (OER) overpotentials, requiring minimal external voltage at pH = 0. This work theoretically demonstrates the potential of the HfS₂/GeSe heterojunction for efficient photocatalysis, offering a new direction for clean energy material design.