Solar Fuels Materials Engineering

这项研究计划的目标是实现一种新型的光催化剂，这种催化剂由富含土壤、低成本、阳光稳定和无毒的材料制成，可以在“人工光合作用”过程中产生太阳能燃料，如甲醇或甲烷，类似于植物和一些细菌在光合作用中利用阳光转化二氧化碳和水的方式。这种材料被称为“人造叶子”。该研究计划将考虑材料性能的最佳组合，包括元素组成的变化、体积和表面结构、物理尺寸和形状、外在和内在缺陷、光学吸收、电子、空穴和离子传输、激子传输和扩散长度、表面吸附和表面扩散，以实现二氧化碳和水到太阳能燃料（如甲烷或甲醇）的快速、选择性和有效的光转化。在这个项目中，实用太阳能燃料光催化剂的选择材料将基于金属氧化物纳米材料的组合。金属氧化物具有广泛的化学和物理性质，这使得它们对开发实用的太阳能燃料异质结构光催化剂具有吸引力，这需要对被认为对二氧化碳还原有用的关键金属氧化物的电子能带能级进行适当的排列。当前能源和气候问题的一个解决方案可能是从自然界的光合作用装置中吸取教训，即树木、植物、草和作物的叶子能够从大气中吸收二氧化碳和水，并在有阳光的情况下将混合物转化为富含能量的碳水化合物，同时释放氧气以维持地球上的生命。如果能找到一种实用的太阳能驱动过程，利用太阳能将二氧化碳转化为富含能量的燃料，如甲烷或甲醇，其总体效率与植物相当或更高，那么仅覆盖地球表面的0.2%，就有可能产生20tw的能量。这将有助于满足全球能源需求，并有助于将大气中的二氧化碳浓度维持在目前的水平。

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 acombination 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.