Highly Efficient and Exceptionally Durable CO₂ Photoreduction to Methanol over Freestanding Defective Single-Unit-Cell Bismuth Vanadate Layers

Abstract

Unearthing an ideal model for disclosing the role of defect sites in solar CO reduction remains a great challenge. Here, freestanding gram-scale single-unit-cell o-BiVO 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-BiVO 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-BiVO layers with rich vanadium vacancies exhibit a high methanol formation rate up to 398.3 μmol g h and an apparent quantum efficiency of 5.96% at 350 nm, much larger than that of single-unit-cell o-BiVO 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 CO photoconversion performances hold great promise for practical implementation of solar fuel production.

CO2 Reduction: From the Electrochemical to Photochemical Approach

“…DFT calculations also predict that the interaction of CO 2 with {010} was stronger than its interactions with {101} or {001} 125. Apart from TiO 2 , other transition metal oxides such as WO 3 and ZrO 2 as well as oxysalts such as titanates (ATiO 3 , A = Na, Sr, Ca, or Pb), tantalates (ATaO 3 , A = Li, Na, or K), niobates (ANbO 3 , A = Na, K), tungstate (Bi 2 WO 6 ), and vanadates (BiVO 4 , InVO 4 , Na 2 V 6 O 16 · x H 2 O) have also been explored in photocatalytic CO 2 reduction 126, 127, 128, 129, 130, 131, 132. Some of them show considerable visible light activity.…”

Atomic‐Level Reactive Sites for Semiconductor‐Based Photocatalytic CO2 Reduction

“…Gao et al introduced vanadium vacancy into BiVO 4 layers by the in situ method. They found that the greater vanadium vacancy density facilitates CO 2 adsorption on BiVO 4 .…”

Dimension‐Matched Zinc Phthalocyanine/BiVO4 Ultrathin Nanocomposites for CO2 Reduction as Efficient Wide‐Visible‐Light‐Driven Photocatalysts via a Cascade Charge Transfer

“…Furthermore,t he photocatalytic activity of BiVO 4 is also unsatisfactory owing to the sluggish charge separation, the limited visible-light utilization, and the low efficiency of charge-induced reactions. [9] Considering sluggish charge separation of BiVO 4 ,w e introduced TiO 2 to generate asolid junction in previous work to help electron transfer from BiVO 4 to TiO 2 ,thus prolonging the lifetimes of visible-light-induced photoelectrons. With the emergence of two-dimensional (2D) materials,u ltrathin sheet-like BiVO 4 is highly desired on account of the minimized diffusion distance and depressed electron-hole recombination.…”