As we are facing increasing challenges of diminishing fossil fuel and global warming in the new century, there is increasing interest in seeking for clean and renewable energy sources. Solar energy represents the ultimate renewable source. Within the central theme of making use of solar energy, there are three essential challenges to be addressed: solar energy harvesting, conversion and storage. Photovoltaic devices, in which light from the sun is directly converted into electricity, is the most popular way to make use of solar energy today. This approach effectively addresses the problems of solar energy harvesting and conversion, but does not address the problem of energy storage. An alternative strategy to harness solar power is through photocatalytic solar fuel generation, in which a photo-assisted electrochemical process directly converts abundant raw materials (e.g. water, carbon dioxide) into hydrogen or other energetic organic species that can serve as chemical fuels. The strategy to directly convert solar energy into chemical energy in the form of chemical fuel simultaneously addresses all three problems of solar energy harvesting, conversion and storage, and therefore can bypass the difficulties of storing the electricity generated in conventional photovoltaic devices.
To this end, we are investigating new designs of photovoltaics devices for more effective use of solar photon energy; developing new types of artificial photosynthesis devices for efficient charge generation, separation, transport and utilization for solar fuel production; and designing new types of energy storage systems with superior gravimetric or volumetric energy storage densities.
- Photovoltaics. Heterogeneous integration of graphene with other layered materials or plasmonic materials can enhance the harvesting and conversion of photon energy.
- Advanced Battery Technologies. For energy storage with superior density, we are exploring a new type of silicon/silicide based air battery system and 3D graphene heterostructures based supercapacitor or pseudocapacitor devices.
- Photocatalysis. By integrating a light-harvesting antenna with a reduction and oxidation catalyst in a well-designed heterostructure, we are developing nanoscale photosynthetic devices for solar fuel generation.