Dimension-matched plasmonic Au/TiO₂/BiVO₄ nanocomposites as efficient wide-visible-light photocatalysts to convert CO₂ and mechanistic insights

Dimension (D)-matched plasmonic Au/TiO₂/BiVO₄ nanocomposites have been successfully constructed by first preparing BiVO₄ nanoflakes via an ion exchange process from BiOCl nanosheets, followed by coupling (001) facet-exposed anatase TiO₂ nanosheets and then modifying plasmonic Au nanorods. The well-designed 1D/2D/2D nanocomposites exhibit exceptional visible-light photocatalytic activities for CO₂ conversion, and these nanocomposites indicate ∼30-fold and ∼60-fold enhancements compared to the resulting BiVO₄ nanoflakes and the previously-reported BiVO₄ nanoparticles, respectively. Based on steady-state surface photovoltage spectroscopy, transient-state surface photovoltage responses, wavelength-dependent photocurrent action spectra and fluorescence spectra related to the amount of produced OH species, it is confirmed that the exceptional photocatalytic activity can be comprehensively ascribed to the following phenomena which result from the fabrication of 2D nanoflakes: increased specific surface area of BiVO₄, coupling of TiO₂ nanosheets to form a new proper-energy platform, which can accept photogenerated electrons from BiVO₄ and plasmonic Au so as to greatly enhance the charge separation, and modified plasmonic Au with the extended wide-visible-light absorption to 660 nm, which can act as the co-catalyst for the transferred electrons to induce reduction reactions. Moreover, dimension matching in the fabricated nanocomposite is very favorable for photogenerated charge transfer and separation. Furthermore, isotope experiments of ¹³CO₂ and D₂O along with electrochemical measurements suggest that the produced H atoms are dominant active radicals, which can initiate the conversion of CO₂.