(Invited) Functional Nanostructures for Highly Efficient Photoelectrochemical Water Splitting

Photoelectrochemical (PEC) water splitting is one of the efficient ways to convert sunlight to the cleanest fuel – hydrogen. The development of photoelectrode materials with a suitable bandgap for efficient light harvesting and fast charge transfer is one of the key challenges for PEC water splitting. In this talk, I will show our recent results using functional nanostructure design to improve the broadband solar absorption and charge transfer process. By growing omnidirectional, densely packed branches on TiO₂ nanowires, we demonstrated a 3D hyperbranched hierarchical TiO₂ nanowire (HHNW) architecture that could significantly enhance the performance of PEC water splitting. Another approach to increase visible light absorption is to use the surface plasmon resonance (SPR) effect. We demonstrated an approach to decorate TiO₂ nanorods (TNRs) with Au nanoparticles (AuNPs) and graphene quantum dots (GQDs). The incident photon-to-current conversion efficiency measurement showed that the PEC activity of the AuNPs and GQDs-loaded TNRs was enhanced in the whole UV-visible region. The experimental analysis indicated that the AuNPs contributed to the surface plasmon resonance (SPR) phenomenon in the UV region and SPR-mediated hot electron injection in the visible region. The GQDs contributed to the improved electron injection in the UV region, multiphoton excitations and hot electron injection in the visible region. The multi-level functionalization of nanostructures have proved to be a synergistic way to realize highly efficient PEC Water Splitting