Plasmon-Sensitized Graphene/TiO Inverse Opal Nanostructures with Enhanced Charge Collection Efficiency for Water Splitting.

In this contribution we have developed TiO inverse opal based photoelectrodes for photoelectrochemical (PEC) water splitting devices, in which Au nanoparticles (NPs) and reduced graphene oxide (rGO) have been strategically incorporated (TiO@rGO@Au). The periodic hybrid nanostructure showed a photocurrent density of 1.29 mA cm at 1.23 V vs RHE, uncovering a 2-fold enhancement compared to a pristine TiO reference. The Au NPs were confirmed to extensively broaden the absorption spectrum of TiO into the visible range and to reduce the onset potential of these photoelectrodes. Most importantly, TiO@rGO@Au hybrid exhibited a 14-fold enhanced PEC efficiency under visible light and a 2.5-fold enrichment in the applied bias photon-to-current efficiency at much lower bias potential compared with pristine TiO. Incident photon-to-electron conversion efficiency measurements highlighted a synergetic effect between Au plasmon sensitization and rGO-mediated facile charge separation/transportation, which is believed to significantly enhance the PEC activity of these nanostructures under simulated and visible light irradiation. Under the selected operating conditions the incorporation of Au NPs and rGO into TiO resulted in a remarkable boost in the H evolution rate (17.8 μmol/cm) compared to a pristine TiO photoelectrode reference (7.6 μmol/cm). In line with these results and by showing excellent stability as a photoelectrode, these materials are herin underlined to be of promising interest in the PEC water splitting reaction.