Enhancing the Photocatalytic Hydrogen Evolution Performance of the CsPbI 3 /MoS 2 Heterostructure with Interfacial Defect Engineering.

Developing highly efficient photocatalysts for the hydrogen evolution reaction (HER) by solar-driven water splitting is a great challenge. Here, we study the atomistic origin of interface properties and the HER performance of all-inorganic iodide perovskite β-CsPbI 3 /2H-MoS 2 heterostructures with interfacial vacancy defects using first-principles calculations. Both CsI/MoS 2 and PbI 2 /MoS 2 heterostructures have strong binding and dipole moment, which are enhanced by interfacial iodine vacancies ( V I ). Because of the nature of type II heterojunctions, photogenerated electrons on the CsPbI 3 side are promptly transferred to the MoS 2 side where HER occurs, and sulfur vacancies ( V S ) spoil this process, acting as surface traps. The formation energies of various defects are calculated by applying atomistic thermodynamics, identifying the growth conditions for promoting V I and suppressing V S formation. The HER performance is enhanced by forming interfaces with lower Δ G H values for hydrogen adsorption on the MoS 2 side, suggesting PbI 2 /MoS 2 with V I to be the most promising photocatalyst.