600 nm-driven photoreduction of CO2 through the topological transformation of layered double hydroxides nanosheets

Conversion of CO2 into useful fuels and chemicals through solar energy offers opportunities to address the crisis of energy for fossil fuels and reduce climate-changing CO2 emissions. In order to make use of solar energy efficiently, fabrication of photocatalysts that can work under longer wavelengths (such as lambda > 600 nm), remains to attract intense attention. Herein, the NiO nanosheets containing an abundant of Ni&O vacancies were fabricated. Through fine-tuning the density of vacancies, we are able to control the selectivity of CH4, CO, and H-2 of the photoreduction CO2 reaction. Furthermore, under irradiation with lambda > 600 nm, the H-2 evolution reaction can be completely suppressed. The DFT+U calculations revealed that under the irradiation wavelength above 600 nm, the photogenerated electrons located on the defect state of NiO could only overcome the Gibbs free energy barrier of CO2 reduction to CH4 and CO, rather than that for H-2 evolution.