Solar Fuels Materials Engineering

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The objective of this research proposal is to realize a new class of photocatalysts made of earth abundant, low cost, sunlight stable and non-toxic materials that can generate solar fuels such as methanol or methane in an 'artificial photosynthetic' process akin to the way plants and some bacteria use sunlight to transform carbon dioxide and water in photosynthesis. Such a material has been referred to as an 'artificial leaf'. The research program will consider the optimal combination of materials properties including variations of elemental composition, bulk and surface structure, physical size and shape, extrinsic and intrinsic defects, optical absorption, electron, hole, and ionic transport, exciton transport and diffusion length, surface adsorption and surface diffusion, to enable fast, selective and efficient photo-transformation of carbon dioxide and water to solar fuels such as methane or methanol. In this program the material of choice for a practical solar fuels photocatalyst will be based upon a combination of metal oxide nanomaterials. The wide ranging chemical and physical properties of metal oxides that make them attractive for the development of a practical solar fuels heterostructured photocatalyst require proper alignment of electronic band energy levels of key metal oxides deemed useful for CO2 reduction. A solution to the current energy and climate problems may be to take a lesson from nature's photosynthetic apparatus, whereby the leaves of trees and plants, grasses and crops are able to sequester carbon dioxide and water from the atmosphere and in the presence of sunlight convert the mixture into energy-rich carbohydrates, with simultaneous release of oxygen to sustain life on earth. If a practical solar-driven process could be found for converting carbon dioxide to energy-rich fuels such as methane or methanol using solar light, with an overall efficiency comparable to or greater than plants, then with just ~0.2 % coverage of the earth's surface, it should be possible to produce 20 TW of energy. This should help to satisfy the global energy demand with the added advantage of helping to maintain atmospheric carbon dioxide concentrations at current levels.