Enhanced photocatalytic CO2 reduction in H2O vapor by atomically thin Bi2WO6 nanosheets with hydrophobic and nonpolar surface

Ultrathin Bi2WO6 nanosheet with hydrophobic and nonpolar surface boosts both the mass-transfer and adsorption of CO2, resulting in a high-efficiency photocatalytic conversion of CO2 in H2O vapor. [Display omitted] •Bi2WO6 with ultrathin structure with hydrophobic and nonpolar surface is successfully prepared.•This ultrathin nanosheet displays 3.2-fold higher CO2 adsorption amount than that of bulk.•This special structure endows a high-efficiency photocatalytic CO2 conversion in H2O vapor without co-catalyst.•The photocatalytic CO2 reduction mechanism is revealed by the in-situ DRIFTS. The artificial carbon dioxide (CO2) photoreduction into useful chemicals utilizing solar energy demands the stable photocatalysts with high-efficiency charge separation and effective CO2 adsorption capacity. For all this, for the first time, Bi2WO6 photocatalysts with atomically thin structure along with hydrophobic and nonpolar surface are successfully designed and prepared using CTAB as assistant. The ultrathin feature with short diffusion distance significantly facilitates the charge separation. The hydrophobic surface, modified by nonpolar long carbon chains of CTA+, boosts both the mass-transfer and adsorption of CO2, meanwhile suppressing the H2O adsorption. Hence, the prepared photocatalyst exhibits a high-efficiency photocatalytic conversion of CO2 in H2O vapor without co-catalyst due to high CO2 concentration and sufficient photogenerated carriers. The photocatalytic mechanisms including adsorption concentration and activation process of CO2 are further revealed by the in-situ diffuse reflectance infrared fourier transform spectra (DRIFTS). As a new feature, linearly adsorbed CO at 2035 cm−1 is found on hydrophobic surface of Bi2WO6, and the absorbance of CO is critical to the next reaction step for CH4 generation. This innovation provides a facile avenue for the design of photocatalysts with remarkable CO2 capture ability to achieve the practical application of photocatalytic CO2 reduction.