TiO2-MnO x-Pt Hybrid Multiheterojunction Film Photocatalyst with Enhanced Photocatalytic CO2-Reduction Activity.

Photocatalytic CO2 conversion into solar fuels has an alluring prospect. However, the rapid recombination of photogenerated electron-hole pairs for TiO2-based photocatalyst hinders its wide application. To alleviate this bottleneck, a ternary hybrid TiO2-MnO x-Pt composite is excogitated. Taking advantage of the surface junction between {001} and {101} facets, MnO x nanosheets and Pt nanoparticles are selectively deposited on each facet by a facile photodeposition method. This design accomplishes the formation of two heterojunctions: p-n junction between MnO x and TiO2 {001} facet and metal-semiconductor junction between Pt and TiO2 {101} facet. Both of them, together with the surface heterojunction between {001} and {101} facets, are contributive to the spatial separation of the photogenerated electron-hole pairs. Thanks to their cooperative and synergistic effect, the as-prepared composite photocatalyst exhibits a promoted yield of CH4 and CH3OH, which is over threefold of pristine TiO2 nanosheets films. The conjecture of the mechanism that selective formation of multijunction structure maximizes the separation and transfer efficiency of photogenerated charge carriers is proved by the photoelectrochemical analysis. This work not only successfully achieves an efficient multijunction photocatalyst by ingenious design but also provides insight into the mechanism of the performance enhancement.