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.

Photocatalytic reduction of CO₂ holds tremendous promise for alleviating the energy crisis. Despite the progress that has been made, there are still some challenges to overcome, such as the realization under real sunlight rather than the simulation condition. In this work, ultrathin Ni₂(OH)(PO₄) nanotubes (NTs) prepared through hydrothermal route are applied as a novel catalyst for photocatalytic reduction of CO₂ under real sunlight. The prepared Ni₂(OH)(PO₄) NTs exhibit a 11.3 µmol·h^-1 CO production rate with 96.1% CO selectivity. Interestingly, Ni₂(OH)(PO₄) NTs have a positive impact on the facilitation of photoreduction in diluted CO₂. Notably, when the system is performed under real sunlight, Ni₂(OH)(PO₄) NTs afford an accumulated CO of ca. 26.8 μmol with 96.9% CO selectivity, exceeding most previous inorganic catalysts under simulated irradiation in the laboratory. Our experimental results demonstrate that the multisynergetic effects induced by surface-OH and the lattice strain serve as highly active sites for CO₂ molecular adsorption and activation as well as electron transfer, hence enhancing photoreduction activity. Therefore, this work provides experimental basis that CO₂ photocatalysis can be put into practical use.