The fate of oxygen on graphene-catalyst in the photocatalytic water splitting reaction

摘要

Graphene has been extensively used in photocatalytic water splitting for enhancing the separation of photogenerated electrons and holes and/or introducing intermediate levels in the band gap to obtain visible-light absorption. However, with a hydrogen uptake, a fundamental understanding of the simultaneous transformation process of oxygen on graphene has always been neglected in most research. To illustrate this important problem, an only 3 layered graphene-exposed photocatalyst (hollow perovskite ZnSnO3-reduced graphene oxide (rGO) nanocubes) is skillfully constructed for the first time, in which similar to 4 nm ZnSnO3 nanoparticle aggregates are closely wrapped up by rGO with C-O-Zn (Sn) chemical bonds connection. Assisted by this ideal robust model without the effect of externally exposed metal oxides, the transformation process of oxygen in water splitting is performed at the C vacancy defect in graphene, which is clarified through in situ Raman spectroscopy and gas chromatography analysis. It is also found that the oxygen of H2O on rGO undergoes a step-by-step dehydrogenation process from the intermediate OH-C and O-C to the final CO2. This research may pave the way for future photocatalytic overall water splitting technologies based on graphene.