Graphene-wrapped Pt/TiO2 photocatalysts with enhanced photogenerated charges separation and reactant adsorption for high selective photoreduction of CO2 to CH4

Abstract

Artificial photosynthesis efficiency for selective CO2 conversion to CH4 as chemical energy-rich molecule is dependent on the photogenerated charges separation and reactant adsorption property of photocatalyst. Here we report a novel fabrication of core-shell-structured photocatalysts of Pt/TiO2-nanocrystals wrapped by reduced graphene oxide (rGO) sheets ((Pt/TiO2)@rGO). The ultrafine anatase TiO2 nanocrystals with coexposed {001} and {101} facets acted as the fountain of the photogenerated charges primitively. Pt nanoparticles (NPs) deposited on the TiO2 nanocrystals can gather and transfer the stimulated electrons originated from anatase TiO2 nanocrystals. The all-solid-state electron multiple transmission (EMT) system with TiO2-nanocrystal(core)-Pt(mediator)-rGO(shell) nanojunction is not only favorable to the vectorial electron transfer of TiO2 → Pt → rGO and enhance the separation efficiency of photogenerated electrons and holes, but also the surface residual hydroxyl and extended π bond of wrapping rGO sheets can improve the adsorption and activation capabilities for CO2 reactant. (Pt/TiO2)@rGO ternary photocatalysts exhibit excellent performance for the multi-electron process of selective photocatalytic CO2 conversion to CH4. Among the prepared catalysts, (Pt/TiO2)@rGO-2 catalyst shows the highest photocatalytic activity and selectivity for CO2 conversion, i.e., the formation rate of CH4 is 41.3 μmol g−1 h−1 and the selectivity of CO2 conversion to CH4 product is 99.1%, and its apparent quantum efficiency for CH4 product is 1.93%. As a heuristic the fabrication of core-shell structured (Pt/TiO2)@rGO photocatalysts will stimulate more novel ideas for application to light-chemical energy conversion.