Oxygen vacancy enhanced photocatalytic activity of Cu₂O/TiO₂ heterojunction

In this study, a method was developed to create oxygen vacancies in Cu₂O/TiO₂ heterojunctions. By varying the amounts of ethylenediaminetetraacetic acid (EDTA), sodium citrate, and copper acetate, Cu₂O/TiO₂ with different Cu ratios were synthesized. Tests on CO₂ photocatalytic reduction revealed that Cu₂O/TiO₂'s performance is influenced by Cu content. The ideal Cu mass fraction in Cu₂O/TiO₂, determined by inductively coupled plasma (ICP), is between 0.075% and 0.55%, with the highest CO yield being 10.22 μmol g^-1 h^-1, significantly surpassing pure TiO₂. High-resolution transmission electron microscopy and electron paramagnetic resonance studies showed optimal oxygen vacancy in the most effective heterojunction. Density functional theory (DFT) calculations indicated a 0.088 eV lower energy barrier for ∗CO₂ to ∗COOH conversion in Cu₂O/TiO₂ with oxygen vacancy compared to TiO₂, suggesting that oxygen vacancies enhance photocatalytic activity.