Atomic‐Level Regulated 2D ReSe ₂ : A Universal Platform Boostin Photocatalysis

Abstract Solar hydrogen (H ₂ ) generation via photocatalytic water splitting is practically promising, environmentally benign, and sustainably carbon neutral. It is important therefore to understand how to controllably engineer photocatalysts at the atomic level. In this work, atomic‐level engineering of defected ReSe ₂ nanosheets (NSs) is reported to significantly boost photocatalytic H ₂ evolution on various semiconductor photocatalysts including TiO ₂ , CdS, ZnIn ₂ S ₄ , and C ₃ N ₄ . Advanced characterizations, such as atomic‐resolution aberration‐corrected scanning transmission electron microscopy (AC‐STEM), synchrotron‐based X‐ray absorption near edge structure (XANES), in situ X‐ray photoelectron spectroscopy (XPS), transient‐state surface photovoltage (SPV) spectroscopy, and transient‐state photoluminescence (PL) spectroscopy, together with theoretical computations confirm that the strongly coupled ReSe ₂ /TiO ₂ interface and substantial atomic‐level active sites of defected ReSe ₂ NSs result in the significantly raised activity of ReSe ₂ /TiO ₂ . This work not only for the first time realizes the atomic‐level engineering of ReSe ₂ NSs as a versatile platform to significantly raise the activities on different photocatalysts, but, more importantly, underscores the immense importance of atomic‐level synthesis and exploration on 2D materials for energy conversion and storage.