Variable metal valence states with band-edge shift over in-situ annealed CuTi-LDH nanosheets for efficient hydrogen and oxygen reduction reactions

The construction of photocatalytic systems with contact interfaces is one of the crucial steps toward the efficient charge separation in photocatalytic reactions. Here, in-situ growth method was utilized to simultaneously obtain ultrathin CuO and TiO2 nanosheets with contact interfaces. The H2 yield of the optimized photocatalyst is ∼ 19.8 mmol/g, ∼ 100 times higher than that of TiO2. In contrast, the samples prepared by physical mixing method only show an H2 yield of ∼ 3.2 mmol/g, fully demonstrating the highly efficient charge separation in in-situ prepared samples. In-situ X-ray photoelectron spectroscopy (XPS) demonstrates the reversible variation of metal valence states and their band-edge shift. This work delivers a new perspective to observe the real-time behavior of metal valances in photocatalysts under light irradiation, which facilities to have a deep understanding of photocatalytic reactions.