This study presents a method to create oxygen vacancies in Cu₂O/TiO₂ heterojunctions, enhancing their photocatalytic activity for CO₂ reduction. By varying the amounts of EDTA, sodium citrate, and copper acetate, Cu₂O/TiO₂ samples with different Cu ratios were synthesized. The optimal Cu mass fraction in Cu₂O/TiO₂ is between 0.075% and 0.55%, with the highest CO yield of 10.22 μmol g⁻¹ h⁻¹, significantly higher than pure TiO₂. The optimal oxygen vacancy in the heterojunction was confirmed through high-resolution transmission electron microscopy and electron paramagnetic resonance. Density functional theory calculations showed that the energy barrier for CO₂ to COOH conversion in Cu₂O/TiO₂ with oxygen vacancies is 0.088 eV lower than in TiO₂, indicating enhanced photocatalytic activity. The study also found that oxygen vacancies improve CO₂ adsorption and catalytic performance. The Cu₂O/TiO₂ heterojunction was prepared using a simple one-step hydrothermal method, showing good dispersion and interface contact. The results suggest that oxygen vacancies in Cu₂O/TiO₂ heterojunctions significantly enhance photocatalytic activity for CO₂ reduction. The optimal Cu content was determined through inductively coupled plasma analysis, and the catalytic performance was evaluated through photocatalytic tests and DFT calculations. The study highlights the importance of controlling oxygen vacancy ratios to improve catalytic performance. The results demonstrate that Cu₂O/TiO₂ heterojunctions with oxygen vacancies are effective for CO₂ reduction, with enhanced charge transfer and catalytic activity. The study provides insights into the role of oxygen vacancies in enhancing photocatalytic performance and offers a promising approach for CO₂ reduction.This study presents a method to create oxygen vacancies in Cu₂O/TiO₂ heterojunctions, enhancing their photocatalytic activity for CO₂ reduction. By varying the amounts of EDTA, sodium citrate, and copper acetate, Cu₂O/TiO₂ samples with different Cu ratios were synthesized. The optimal Cu mass fraction in Cu₂O/TiO₂ is between 0.075% and 0.55%, with the highest CO yield of 10.22 μmol g⁻¹ h⁻¹, significantly higher than pure TiO₂. The optimal oxygen vacancy in the heterojunction was confirmed through high-resolution transmission electron microscopy and electron paramagnetic resonance. Density functional theory calculations showed that the energy barrier for CO₂ to COOH conversion in Cu₂O/TiO₂ with oxygen vacancies is 0.088 eV lower than in TiO₂, indicating enhanced photocatalytic activity. The study also found that oxygen vacancies improve CO₂ adsorption and catalytic performance. The Cu₂O/TiO₂ heterojunction was prepared using a simple one-step hydrothermal method, showing good dispersion and interface contact. The results suggest that oxygen vacancies in Cu₂O/TiO₂ heterojunctions significantly enhance photocatalytic activity for CO₂ reduction. The optimal Cu content was determined through inductively coupled plasma analysis, and the catalytic performance was evaluated through photocatalytic tests and DFT calculations. The study highlights the importance of controlling oxygen vacancy ratios to improve catalytic performance. The results demonstrate that Cu₂O/TiO₂ heterojunctions with oxygen vacancies are effective for CO₂ reduction, with enhanced charge transfer and catalytic activity. The study provides insights into the role of oxygen vacancies in enhancing photocatalytic performance and offers a promising approach for CO₂ reduction.