Pt-loading reverses the photocatalytic activity order of anatase TiO2 {001} and {010} facets for photoreduction of CO2 to CH4

It is well known that different crystal facets of TiO2 have different surface electronic and atomic structures, which can influence the photocatalytic performance, and appropriate noble metal-loading usually improves the photocatalytic activity. Herein we demonstrate that Pt-loading can reverse the photocatalytic activity order of anatase TiO2 {0 0 1} facets (TiO2-0 0 1) and {0 1 0} facets (TiO2-0 1 0) for the photoreduction of CO2 to CH4. This new phenomenon was discussed on the bases of the experimental data including attenuated total reflectance Fourier transform infrared (ATR-IR) spectra, CO2 temperature programmed desorption (CO2-TPD) curves, transmission electron microscopy (TEM) images and time-resolved photoluminescence (PL) spectra. It is found that the higher photocatalytic CO2 reduction activity of TiO2-0 1 0 without Pt-loading can be attributed to its larger CO2 adsorbed amount and longer charge lifetime as compared with TiO2-0 0 1, while the Pt nanoparticles loaded on TiO2-0 0 1 can more efficiently enhance the photoinduced carrier separation efficiency than that on TiO2-0 1 0, and therefore resulting in a photoactivity higher than the Pt-loaded TiO2-0 0 1. The above results provide an important indication about the effects of Pt-loading on the photocatalytic CO2 reduction activity of anatase TiO2 with different exposed facets, and shed light on the fabrication of novel nanostructured photocatalysts through morphological control for high conversion efficiency in the CO2 resource utilization.