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

Abstract

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.