Construction of graphene oxide-coated zinc tetraphenyporphyrin nanostructures for photocatalytic CO2 reduction to highly selective CH4 product

The zinc-based photocatalysts for CO 2 reduction have attracted increasing attention, however, usually exhibit low CO 2 -to-CH 4 selectivity. Here, the graphene oxide (GO)-coated zinc tetraphenylporphyrin (ZnTPP/GO) nanocomposites are successfully synthesized through a simple method. It is found that with the increase of GO content, the crystallinity of ZnTPP nanocrystals enhances with the size decrease, and then the light absorption can easily match with the solar spectrum. The optimal ZnTPP/GO sample exhibits the CH 4 evolution rate of 41.6 μmol g −1  h −1 and CH 4 selectivity of >95%, which are higher than those of ZnTPP nanocrystals (7.8 μmol g −1  h −1 and 50.3%). The systematic characterizations confirm that the generation of axial coordinated Zn O C bonds between ZnTPP and GO plays a key role in the formation of ZnTPP/GO nanostructure and their synergic effect on photocatalytic CO 2 reduction. The encapsulation of GO on ZnTPP nanocrystals not only promotes the CO 2 adsorption, interfacial reaction, and stability, but also accelerates the separation of photoinduced carriers on ZnTPP (0.1 ps vs. 425.9 ps), the transportation from ZnTPP to GO (2.3 ps vs. 83.6 ps), and their final enrichment on GO. This work provides a new strategy to apply graphene and organic nanomaterials in artificial photosynthesis.