Photocorrosion suppression and photoelectrochemical (PEC) enhancement of ZnO via hybridization with graphene nanosheets

Graphene-ZnO nanocomposites with different morphologies (nanoparticles and nanorods) were synthesized by alkali precipitation and solvothermal process. The influence of graphene nanosheets on photocatalytic and photoelectrochemical (PEC) activity of graphene-ZnO nanorods (ZnO/GNR) and graphene/ZnO nanoparticles (ZnO/GNP) was investigated. ZnO/GNR showed greatly increased photocatalytic degradation of methyl orange (MO): 2-, 2.5- and 3.5-fold higher under UV light and 1.6-, 4.7-, and 11-fold higher under visible light than that for ZnO/GNP, ZnO NR and ZnO NP, respectively. In addition, ZnO/GNR showed remarkable photocorrosion suppression (∼0.5%) compared to 10, 35 and 45% for ZnO/GNP, ZnO NR and ZnO NP, respectively. Furthermore, PEC results indicated a remarkable 6-fold enhancement photocurrent density for ZnO/GNR compared to ZnO NR. This enhancement is attributed to the crucial role of graphene in the electron transfer from ZnO NR into graphene sheets increasing the electron lifetime, leading to a minimized charge recombination.