Improved photocatalytic activity of porous ZnO nanosheets by thermal deposition graphene-like g-C3N4 for CO2 reduction with H2O vapor

Porous ZnO nanosheets (PNS-ZnO) were prepared by calcining ZnS(en)(0.5) (en = ethylenediamine) nanosheets in air, and g-C3N4 (g-CN) nanofilms were coated on the surface of PNS-ZnO by thermal deposition using bulk g-C3N4 as precursor. Experimental results showed that the graphene-like g-C3N4 could be deposited on the surface of ZnO to form nanocomposites with core/shell structure. After the loading of g-CN, the light absorption and chemical adsorption of CO2 over PNS-ZnO were improved obviously and the recombination of photogenerated electron and hole was greatly depressed due to the formation of heterojunction between PNS-ZnO and g-CN. All PNS-ZnO@g-CN nanocomposites exhibited much higher photocatalytic activity for CO2 reduction with H2O vapor when compared to pure PNS-ZnO and bulk g-CN. The loading amount of g-CN had significant influence on the light absorption and photocatalytic activity, and PNS-ZnO@g-CN-0.4 exhibited the best photocatalytic performance, for which H-2, CH4 and CO production rates of 22.7, 30.5 and 16.8 mu mol/g(cat)/h can be obtained, respectively.