Opposite photocatalytic activity orders of low-index facets of anatase TiO2 for liquid phase dye degradation and gaseous phase CO2 photoreduction

Abstract

We firstly demonstrate the opposite photocatalytic activity orders of low-index facets of anatase TiO₂ in the liquid phase for rhodamine B (RhB) photocatalytic degradation and in the gaseous phase for the photoreduction of CO₂ to CH₄. The photocatalytic activity order in the liquid phase for RhB photocatalytic degradation is revealed as {001} > {101} > {010}, whereas the photocatalytic activity order {010} > {101} > {001} is found in the gaseous phase for the photoreduction of CO₂ to CH₄. The atomic arrangement of the different facets, UV-vis diffuse reflectance spectra, photoluminescence spectra and attenuated total reflectance Fourier transform infrared spectroscopy analysis show that the photoactivity order in the gas phase for the photoreduction of CO₂ to CH₄ mainly depends on the CO₂ molecule adsorption properties on the different exposed facets, and the separation efficiency of the photo-generated carriers determines the photoactivity order for the dye degradation reaction in the liquid phase. These findings also provide a new direction to design efficient photocatalysts and the tuning of their photoreactivity for environmental and energy applications.