Site-selective introduction of MnO co-catalyst onto gold nanocubes via plasmon-induced charge separation and galvanic replacement for enhanced photocatalysis.

For energy harvesting with plasmonic photocatalysis, it is important to optimize geometrical arrangements of plasmonic nanomaterials, electron (or hole) acceptors, and co-catalysts so as to improve the charge separation efficiency and suppress charge recombination. Here, we employ a photocatalytic system with Au nanocubes on TiO and introduce MnO as an oxidation co-catalyst onto the nanocubes via site-selective oxidation based on plasmon-induced charge separation (PICS). However, it has been known that PbO is the only material that can be deposited onto Au nanomaterials through PICS with sufficient site-selectivity. Here we addressed this issue by introducing an indirect approach for MnO deposition via site-selective PbO deposition and subsequent galvanic replacement of PbO with MnO. The indirect approach gave nanostructures with MnO introduced at around the top part, bottom part, or entire surface of the Au nanocubes on a TiO electrode. The activity of those plasmonic photocatalysts was strongly dependent on the location of MnO. The key to improving the activity is to separate MnO from TiO to prevent recombination of the positive charges in MnO with the negative ones in TiO.