Space confinement of physical deposited Au nanoparticles on a three-dimensional-branched TiO2 photoanode for efficient photoelectrochemical overall water splitting

In this paper, we present an effective route for boosting the photoelectrochemical overall water splitting to produce hydrogen and oxygen by modified TiO2 nanowire arrays (NWAs) photoanode. Such modification includes the synthesis of branched TiO2 NWAs and followed by the deposition of Au nanoparticles (NPs) via the magnetron sputtering and post-annealing for the dewetting of Au films. The physical deposition of Au on the TiO2 substrate with a hierarchical structure provides a feasible strategy to produce metal NPs with uniform size and distribution by the space confinement of the branched TiO2 NWAs. Those Au NPs rendered the intensified visible light absorption in a narrow band region due to the surface plasmon resonance (SPR) effect. The amplified electromagnetic field through the SPR excitation of the Au NPs and their passivation upon the surface of TiO2 NWAs led to the efficient generation and transfer of charge carriers. The synergistic effect between branched TiO2 NWAs and Au NPs resulted in the drastic enhancement of the photoelectrochemical overall water splitting to produce hydrogen and oxygen in the stoichiometric ratio. This work provides a facile method for the preparation of hierarchical metal/semiconductor composite photoelectrode with great potential in the efficient photoelectrochemical water splitting for hydrogen energy production and other applications in solar energy conversion.