Investigations on the effect of Cu2+/Cu1+ redox couples and oxygen vacancies on photocatalytic activity of treated LaNi1−xCuxO3 (x=0.1, 0.4, 0.5)

Perovskite-like oxides LaNi1−xCuxO3 (x = 0.1, 0.4, 0.5) were prepared by means of the citric acid complexing method. TPR revealed the incorporation of Cu into the perovskite lattice increased the reducibility of the catalyst. After LaNi1−xCuxO3 were pretreated in H2 for 2 h at certain low temperature, the material still retained its perovskite structure and oxygen vacancies were generated in the lattice. DRS showed that narrowing of band-gap of reduced LaNi1−xCuxO3 was governed by the crystalline structure and the defect in the catalyst. In the photocatalytic water splitting experiment, 200 and 250°C-reduced LaNi0.6Cu0.4O3, 200°C-reduced LaNi0.5Cu0.5O3 possessed the high and colse catalytic activity. XPS showed that the molar ratio of Cu2+/Cu1≈1 and lattice oxygen/adsorb oxygen ≈ 0.2 in the catalysts had high catalytic activity. According to the outcome of our experiments, we conclude that there is a balance relation either between oxygen vacancies and catalytic activity or between Cu2+/Cu1+ redox couples and catalytic performance of these materials for hydrogen production from photocatalytic water splitting. Enhancement of hydrogen yield can be attributed to the small band-gap and the lowering the recombination probability for electron-hole pairs.