Promoted oxygen activation of layered micro-mesoporous structured titanium phosphate nanoplates by coupling nano-sized δ-MnO2 with surface pits for efficient photocatalytic oxidation of CO

Abstract

It is highly desired to fabricate efficient micro-mesoporous structured photocatalysts with strong oxygen activation ability for CO oxidation. Herein, a layered micro-mesoporous structured titanium phosphate (L-MMS-TiP) with high photocatalytic activity for CO oxidation has been successfully synthesized by a two-step solvothermal method. The photocatalytic activity of resulting L-MMS-TiP could be greatly improved by coupling a proper amount of nano-sized δ-MnO2, especially for that with surface pits. The improved activities are mainly attributed to the roles of coupled δ-MnO2 in enhancing photogenerated charge separation and promoting oxygen activation, which is revealed based on measurements of the steady-state surface photovoltage spectra, nitroblue tetrazolium absorption spectra, electron paramagnetic resonance spectra and in situ DRIFTS spectra. Interestingly, the photocatalytic activity of pitted δ-MnO2-coupled L-MMS-TiP is superior to that of P25 TiO2, even much higher than that of Au-coupled L-MMS-TiP. Significantly, δ-MnO2-coupled L-MMS-TiP also has excellent oxidation removal effect for other harmful or even mixed gases. Moreover, it is confirmed that δ-MnO2 with the two-dimensional structure is the best one to couple L-MMS-TiP for photocatalytic CO oxidation among all four kinds of crystal phases and compared with other transitional metal oxides. This work opens up a new way to develop a layered micro-mesoporous structure-based nanocomposite, and further improve the photocatalytic activity by promoting oxygen activation with two-dimensional pitted δ-MnO2.