Tuning the Selectivity Towards Solar Fuels via Manipulation of Photocharge Transfer of Oxide Photocatalysts

Solar fuels produced from photocatalytic reactions offer a promising solution in addressing the clean energy demand as well as helping the society marching towards carbon neutrality. Although solar hydrogen is the most studied type of solar fuels, the challenges in storage, transportation and safe handling of hydrogen have prompted the consideration of other solar fuels. Photochemical reduction of unwanted carbon dioxide into green methane and photochemical oxidation of water into hydrogen peroxide are two interesting redox reactions which lead to the formation of solar fuels. Both the green methane and hydrogen peroxide fromrenewable resources are valuable alternative fuels. The production of green methane and hydrogen peroxidee are often accompanied with the simultaneous generation of other by-products as a result of un-regulated charge transfer between the photocatalyst and the reactant molecules. In this project, innovative methods to improve the charge manipulation over the electron transfer behavior on oxide photocatalysts will be developed via the principles of crystal orientation, defect introduction and surface functionalization. The governing factors in transferring photogenerated charges across the surface of photocatalyst will be investigated using a combination of the state-of-art timeresolved and operando spectroscopic techniques. Successful execution of this project will lead to the expansion of new knowledge in regulating charge transfer behavior in semiconductors with application not limited to photocatalysis. The ultimate goal in efficiently using solar energy in the form of chemical fuels (such as clean hydrogen, green methane and hydrogen peroxide fuels) is achievable through careful design and thorough understanding of photocatalyst with satisfactory selectivity towards specific product. This project will contribute to the development of functional oxide photocatalysts with higher efficiency, selectivity and stability that has not been possible in the past. Given the strategic solar-geographical position of Hong Kong and the target of achieving carbon neutrality, utilization of sunlight in the form of solar fuels (via photocatalytic redox reactions) is a promising option to overcome the issues of energy insecurity and environmental protection.