Highly Efficient and Exceptionally Durable CO₂ Photoreduction to Methanol over Freestanding Defective...

Unearthing an ideal model for disclosing the role of defect sites in solar CO₂ reduction remains a great challenge. Here, freestanding gram-scale single-unit-cell o-BiVO₄ layers are successfully synthesized for the first time. Positron annihilation spectrometry and X-ray fluorescence unveil their distinct vanadium vacancy concentrations. Density functional calculations reveal that the introduction of vanadium vacancies brings a new defect level and higher hole concentration near Fermi level, resulting in increased photoabsorption and superior electronic conductivity. The higher surface photovoltage intensity of single-unit-cell o-BiVO₄ layers with rich vanadium vacancies ensures their higher carriers separation efficiency, further confirmed by the increased carriers lifetime from 74.5 to 143.6 ns revealed by time-resolved fluorescence emission decay spectra. As a result, single-unit-cell o-BiVO₄ layers with rich vanadium vacancies exhibit a high methanol formation rate up to 398.3 μmol g^-1 h^-1 and an apparent quantum efficiency of 5.96% at 350 nm, much larger than that of single-unit-cell o-BiVO₄ layers with poor vanadium vacancies, and also the former's catalytic activity proceeds without deactivation even after 96 h. This highly efficient and spectrally stable CO₂ photoconversion performances hold great promise for practical implementation of solar fuel production.