Plasmon-Accelerated Water Oxidation at Ni-Modified Au Nanodimers on TiO₂ Single Crystals

The oxygen evolution reaction via water-splitting is essential in the solar production of chemical fuels. However, the high overpotential limits the conversion efficiency, even when precious metal catalysts are used to drive it. Plasmonic metal–semiconductor systems can potentially overcome this problem, because hot electrons generated by localized surface plasmon resonance are rapidly injected into the semiconductor, and concentrated hot holes oxidize water on the catalysts for oxygen evolution. Using Ni-modified Au/TiO2, we investigated distinct Raman spectral characteristics of water-oxidation intermediates at electrochemical potentials near the flat-band potential of TiO2. Specifically, in situ electrochemical surface-enhanced Raman spectroscopy was performed over the pH range 7–13. Significantly enhanced photocurrents at near-neutral conditions were generated with low-energy photons (1.58 eV), providing the first robust experimental evidence that nickel-based catalysts accelerated the four-electron multistep reaction via plasmon-assisted water oxidation.