Synthesis of N-doped graphene-functionalized Zn1.231Ge0.689N1.218O0.782 solid solution as a photocatalyst for CO2 reduction and oxidation of benzyl alcohol under visible-light irradiation

Abstract

N-doped graphene/Zn_1.231Ge_0.689N_1.218O_0.782 (N-graphene/ZnGeON) hybrid composites were assembled through electrostatic adsorption of positively charged Zn₂GeO₄ nanorods with negatively charged graphene oxide (GO) and calcination using a high temperature in situ nitridation technique under NH₃ flow. During this two-stage chemical process, the ZnGeON solid solution is tightly wrapped by ultrathin N-graphene sheets. Detailed investigations indicated that the N-graphene/ZnGeON hybrids could not only catalyze the evolution of CH₄ from the photocatalytic reaction of CO₂ and H₂O, but also catalyze the evolution of benzaldehyde from the photocatalytic reaction of benzyl alcohol and O₂ under visible-light irradiation. The enhanced photocatalytic performances observed over N-graphene/ZnGeON hybrids can be traced to the existence of highly conductive N-graphene sheets which provide strong interfacial contact with the ZnGeON solid solution. It is suggested that the synergistic effect between ZnGeON and N-graphene in the hybrids is beneficial for photogenerated carrier transfer from ZnGeON to N-graphene, and it was found that the latter is used not just as an electron acceptor and mediator, but as a co-catalyst for the photoreduction of CO₂ and oxidation of benzyl alcohol. This work has proven to be a technologically feasible and chemically efficient strategy for the development of N-graphene-involved hybrid semiconductor photocatalysts toward many desired applications.