Oxygen-vacancy-anchoring NixOy loading towards efficient hydrogen evolution via photo-thermal coupling reaction

Oxygen vacancy (V-O) is a significant component in defect engineering. The present work reports the anchoring effects of initial V-O for further loading modifications and the reducing capacity of photoinduced V-O for pure water splitting. Herein, we propose Ni-loaded Cu-doped TiO2 (NCT) materials by successive doping and loading. The continuously added Ni ions should accumulate around the V(O)s and gradually grow into complete nickel oxide crystals, achieving a higher average valence state of the Ni species. NiO crystals can be detected on a 0.5% NCT sample, while the structure of Ni2O3 has been confirmed with a higher nickel mass ratio. Moreover, the introduction of nickel oxide effectively improves the photochemical and electrochemical performance by the interface charge separation, finally reaching an H-2 yield of 30.6 mu mol/g-cat on 0.5% NCT for V-O-based photo-thermal coupling reaction, which consists of V-O generation in photo and V-O consumption in thermal environment. In situ infrared spectroscopy further indicated that the presence of high valence state nickel oxide hindered the H-2 formation but effectively promoted the conventional oxidizing reaction, with an H-2 yield of 20.6 mmol/g-cat in a methanol-water reaction on the 2.0% NCT material. In summary, V-O controls the morphological structure of Ni loading and produces diverse effects for reactions with dissimilar mechanisms, which provides a novel way to design modifications for promoting various chemical reactions. (C) 2021 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.

Automated summary

This study focuses on the importance of oxygen vacancy (V-O) in defect engineering, prepares Ni-loaded Cu-doped TiO2 (NCT) materials through successive doping and loading, and finds that the presence of high valence state nickel oxide produces diverse effects for reactions with different mechanisms.