Two-dimensional In2Se3/In2SeTe heterojunction: Water-splitting photocatalyst with Ultra-low exciton binding and Ultra-high solar-to-hydrogen efficiency

Due to the environmental and energy crises, scientific progress on new energy has always been highly anticipated, and how to more efficiently produce hydrogen through solar water splitting is an urgent topic. For this purpose, a two-dimensional (2D) stable In2Se3/In2SeTe heterojunction (HJ) is constructed and investigated by employing first-principles calculations herein. The exciton binding energy of In2Se3/In2SeTe is as low as similar to 0.20 eV, and its conversion efficiency of solar to hydrogen (STH) for this HJ reaches 27.5%. Also, its hydrogen and oxygen evolution reactions can occur successfully without a cocatalyst. Given these characteristics, In2Se3/In2SeTe is a hopeful candidate for hydrogen water splitting. Moreover, for the reliability and efficiency of the exciton binding energy of 2D HJs, which strongly affects hydrogen production, the dielectric constant in the Mott-Wannier hydrogenic model should be reconsidered by including the effective thickness. In total, this manuscript not only proposes a new 2D photocatalytic material but also theoretically contributes to the Mott-Wannier hydrogenic model.