The solar-driven photo(electro)catalytic chemical process is a key technology for sustainable utilization of solar energy. It has beena widely applied to environmental remediation and solar fuel production. The dual functional photo(electro)catalytic process can achieve the water treatment along with the simultaneous recovery of energy (e.g., H₂ and H₂O₂) or resource (e.g., metal ions).

Hydrogen peroxide (H₂O₂), a carbon-free energy carrier and an environment-friendly oxidant, has been widely applied in chemical and environmental processes. H₂O₂ production by photocatalytic and photoelectrochemical (PEC) method that uses sunlight, water and molecular oxygen only is a green and sustainable alternative to the conventional production method.

Photocatalysis is an ideal method for removing volatile organic compounds (VOCs) present at low concentrations in indoor environment because it operates at ambient temperature and pressure to degrade them to CO₂ and H₂O. Photocatalysis can be particularly suitable for removing low concentration pollutants (sub-ppm levels) in indoor environments where the conventional adsorption technologies are not very efficient.

Advanced redox processes have been intensively studied for efficient removal of recalcitrant contaminants with high chemical stability or low biodegradability in wastewater. For energy-sustainable applications of the redox processes, it is essential to develop a system that efficiently produces reactive oxygen species (ROS) such as hydroxyl radical and superoxide anion. Various methods such as photolysis, photocatalysis, electrolysis, and sonolysis have been developed to efficiently produce oxidants (e.g., ^●OH) from dioxygen and water molecule or reductants like energetic electrons.

Ice is one of the most ubiquitous solids on Earth, being present in the atmosphere, terrestrial surface, and ocean environment. Many environmental reactions taking place in ice are significantly different compared to aqueous counterparts. We have been investigating various homogeneous and heterogeneous chemical reactions in frozen solutions, especially those which have environmental significance and found that many environmental chemical reactions taking place in frozen solutions are significantly different compared to aqueous counterparts.