Plasmon-Sensitized Graphene/TiO₂ Inverse Opal Nanostructures with Enhanced Charge Collection Efficiency for Water...

In this contribution we have developed TiO₂ inverse opal based photoelectrodes for photoelectrochemical (PEC) water splitting devices, in which Au nanoparticles (NPs) and reduced graphene oxide (rGO) have been strategically incorporated (TiO₂@rGO@Au). The periodic hybrid nanostructure showed a photocurrent density of 1.29 mA cm^-2 at 1.23 V vs RHE, uncovering a 2-fold enhancement compared to a pristine TiO₂ reference. The Au NPs were confirmed to extensively broaden the absorption spectrum of TiO₂ into the visible range and to reduce the onset potential of these photoelectrodes. Most importantly, TiO₂@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 TiO₂. 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 TiO₂ resulted in a remarkable boost in the H₂ evolution rate (17.8 μmol/cm²) compared to a pristine TiO₂ photoelectrode reference (7.6 μmol/cm²). 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.