Graphene bridge in transferring hot electrons from plasmonic Ag nanocubes to TiO2 nanosheets for enhanced visible light photocatalytic hydrogen evolution

The integration of plasmonic metal with wide-bandgap semiconductor is a promising approach to utilize the visible light without compromise of the redox ability of photogenerated charge carriers. However, a larger work function of metal than that of semiconductor is indispensable to enable the injection of hot electrons from plasmonic metal to semiconductor. In this paper, we demonstrated that reduced graphene oxide (rGO) nanosheets as conductive bridge can breakthrough the restriction and transfer hot electrons from Ag of smaller work function to TiO2 of larger work function. In the design, both of the Ag nanocubes and TiO2 nanosheets are co-deposited on the surface of rGO nanosheets to form Ag-rGO-TiO2 structure, which was characterized by XRD, TEM, Raman and XPS spectra. On one hand, the Ag-rGO interface facilitates the transfer of hot electrons from Ag to rGO through conductor conductor contact. On the other hand, the new formed Schottky junction on the rGO-TiO2 interface further pumps the transferred electrons to the surface of TiO2 for photocatalytic reduction reaction resulted from the larger work function of rGO than that of TiO2. Enabled by this unique design, the hydrogen production activity achieved under visible light irradiation is dramatically enhanced in comparison with that of Ag-TiO2 counterpart with the direct contact between the same Ag nanocubes and TiO2 nanosheets. This work represents a step toward the rational interfacial design of plasmonic metal-semiconductor hybrid structures for broad-spectrum photocatalysis.