A perspective on solar-driven water splitting with all-oxide hetero-nanostructures

A perspective on the design of all-oxide heterostructures for application in photoelectrochemical cells for solar water splitting is provided. Particular attention is paid to those structures which possess nanoscale feature dimensionality, as structures of this type are most likely to utilize the benefits afforded by the formation of oxide heterojunctions and likely to show functional behavior relating to the interfacial region. In the context of this discussion, a novel hetero-nanostructure array, based on quantum-confined and visible light-active iron(III) oxide nanostructures and their surface modification with tungsten(VI) oxide, is introduced. The heterostructure architecture is designed to combine the functionality of the consituent phases to address the primary requirements for electrodes enabling the efficient generation of hydrogen using solar energy: visible light activity, chemical stability, appropriate bandedge characteristics, and potential for low-cost fabrication. Photoelectrochemical characterization for solar hydrogen/oxygen generation indicates the presence of unexpected minority carrier transfer dynamics within the oxide hetero-nanostructures, as observed additionally by ultrafast transient absorption spectroscopy.