Formation of a Dyadic Metal Oxide Heterostructure from a WO3 Nanoparticle Thin Film and TiO2 Nanoparticles for Efficient Separation of Charge

It is important to create more efficient and cheaper pathways to produce alternative fuel sources. One promising energy source is the utilization of sunlight for conversion via solar cells; however, it is both costly and labor intensive to produce commercial silicon solar cells. Alternatively, solar energy can be harvested and turned into fuel through creation of an exciton that can then be separated. Metal oxide heterostructures are a promising means for efficient charge separation. Metal oxides are abundant, resistant to photocorrosion, cheap, and non-toxic, which make them ideal for large-scale solar energy applications. WO₃ and TiO₂ are two metal oxides of interest to create charge separation because of their respective band alignments. The nanoscale heterostructure was synthesized by functionalizing the WO₃ nanoparticle thin film with an azide group. The TiO₂ nanoparticles were functionalized with a ligand bearing an alkyne group. The metal oxides were then linked via a Cu alkyne-azide cycloaddition. X-ray photoelectron spectroscopy elemental measurements and scanning electron microscopy images both confirmed that TiO₂ nanoparticles completely functionalize the WO₃ nanoparticle thin film. Time-resolved surface photovoltage confirmed the ability of the WO₃-TiO₂ nanoscale heterostructure to separate charge. Experimental results demonstrate the creation of a dyadic metal oxide structure that has a conjugated linkage which allows for charge transfer and separation. This research shows the ability to functionalize and link two nanoscale metal oxides with different band alignments for the purpose of charge transfer.