Boosted photoreduction of diluted CO₂ through oxygen vacancy engineering in NiO nanoplatelets

Converting carbon dioxide (CO₂) to diverse value-added products through photocatalysis can validly alleviate the critical issues of greenhouse effect and energy shortages simultaneously. In particular, based on practical considerations, exploring novel catalysts to achieve efficient photoreduction of diluted CO₂ is necessary and urgent. However, this process is extremely challenging owing to the disturbance of competitive adsorption at low CO₂ concentration. Herein, we delicately synthesize oxygen vacancy-laden NiO nanoplatelets (r-NiO) via calcination under Ar protection to reduce diluted CO₂ through visible light irradiation (> 400 nm) assisted by a Ru-based photosensitizer. Benefitting from the strongly CO₂ adsorption energy of oxygen vacancies, which was confirmed by density functional calculations, the r-NiO catalysts exhibit higher activity and selectivity (6.28 × 10³ µmol·h⁻¹·g⁻¹; 82.11%) for diluted CO₂-to-CO conversion than that of the normal NiO (3.94 × 10³ µmol·h⁻¹·g⁻¹; 65.26%). Besides, the presence of oxygen vacancies can also promote the separation of electron-hole pairs. Our research demonstrates that oxygen vacancies could act as promising candidates for photocatalytic CO₂ reduction, offering fundamental guidance for the actual photoreduction of diluted CO₂ in the future.