Photocatalyst/Functionalized-graphene Composites: Enhancing Charge Transport, Reactivity and Selectivity

Incorporation of graphene has in the recent years resulted in breakthrough in the field of heterogeneous photocatalysis. Enhancements in photocatalytic activities, in an order of magnitude, have been reported by simply interfacing reduced-graphene-oxide (rGO) with photocatalytic materials. This is attributed to the improved charge transfer at the rGO-photocatalyst interface, which in turn enhances the overall charge separation. Considering the infancy of such system, much remains to be explored in terms of eliciting the full potential of the rGO-photocatalyst composites, especially for complex systems.It is within the scope thata general and novel concept, on the designing of “functionalized-rGO-photocatalysts”is being proposed for the first time, targetingthe enhanced interfacial charge transport,andthe engineering of active sites on rGO.The first criterion involves the chemical interfacing of rGO with photocatalysts using different chemical linkers and conjugation strategies. The linkers provide enhanced and favorable bridging paths for which photocharges can be transferred interfacially. Thestrategy is an improvement to the currently available rGO-photocatalysts,which rely on physical van der Waals contacts and to a smaller extent, the photocatalysts attachment through carboxylic moieties at the edges of rGO. The second criterion involves the grafting of “extended reactive sites”, including facet-selective metal deposits and capturing-molecules, onto rGO for selective-targeting of photoreactions. Through the design of reactive-sites-specific rGO, it is possible tosegregate redox sites to minimize crossing paths of electrons and holes,thereby enhancing the overall quantum efficiencies.A number of carefully selected probe reactions will be carried out, encompassing the oxidation of a series of organic compounds and the remediation of heavy metals. A wide array of reactions is necessary to provideholistic appreciation of the specific mechanism that the different functionalized-rGO-photocatalysts target.Another function to be investigated is the sensitization of photocatalysts through the grafting of quantum dots on rGO. The sensitizer-rGO-photocatalyst composites will be assessed for the photoelectrochemical water splitting.Success of the proposed research will lead to the next-generation-photocatalysts that are not only defined by high quantum efficiencies, but are also selective and reactions-tunable. Specifically to this proposal, the first of such prototypes will be targeted towards the remediation of wastewater and H2production. The strategy to be demonstrated in this proposal is so general that it can be flexibly applied for other photocatalytic reactions, for example, CO2reduction. The fundamentals to be developed through the work are even applicable to other fields, e.g. solar cells and biosensors.