TiO2表面光催化固氮反应机理的理论研究和更高效催化剂的筛选

Ammonia is an indispensable material for the production of fertilizers and other products. The industrial synthesis of ammonia by the Haber-Bosch method requires a huge amount of energy and emits enormous carbon dioxide, which in turn exacerbates the growing energy and environmental problems. It is urgent to find a sustainable green way to synthesize ammonia. In recent years, photocatalytic nitrogen fixation has attracted increasing attention. Among the photocatalysts studied, TiO2 not only exhibits high nitrogen fixation activity and selectivity, but also has the advantages of stability, non-toxicity and abundant reserves. In addition, its activity can be greatly enhanced by transition metal doping. Therefore, it is a promising photocatalytic nitrogen-fixing material. However, limited by characterization techniques, the existing experimental results still cannot provide an understanding of the reaction at the fundamental level. This seriously hampers the design of more efficient catalysts and the application of photocatalytic nitrogen fixation technology. By first-principles calculation, the applicant will provide the mechanism of the reaction at the atomic scale on the surfaces of TiO2; reveal the structure-activity relationship of the catalyst; clarify the influence of the dopant atom on the activity of TiO2; screen out transition metal doped TiO2 with higher nitrogen-fixation activity through the study of the scaling relation of the intermediates. The project is important for guiding further theoretical and experimental research.

氨是生产化肥等产品不可缺少的原料。工业上通过Haber-Bosch方法合成氨，需要消耗大量的能量，并排放大量的二氧化碳，进而加剧日益严重的能源与环境问题。寻找绿色的可持续方法合成氨刻不容缓。近年来，光催化固氮受到越来越多的重视。在众多被研究的光催化剂中，TiO2不仅表现出很强的固氮活性和选择性，还具有稳定，无毒，储量丰富等优点。并且它的活性还可通过过渡金属掺杂大幅提高。因而是一个很有应有前景的光催化固氮材料。不过受表征手段的限制，现有的实验结果还无法提供对该反应根本层面的理解。这严重阻碍了更高效催化剂的设计和光催化固氮技术的应用。申请人将通过第一性原理的计算，提供TiO2表面上该反应原子尺度的机理，揭示催化剂构效关系，阐明掺杂原子对TiO2活性的影响，并通过反应中间物标度关系的研究，筛选出固氮活性更高的过渡金属掺杂的TiO2。该项目对指导进一步的理论和实验研究有重要意义.

TiO2是很有应用前景的固氮催化剂。目前的研究存在反应机理不明，Fe掺杂元素作用不清，催化剂性能不高等问题。本项目通过研究anatase相和rutile相不同晶面上的氮气还原反应(NRR)机理，揭示了表面氧空位是反应的最佳活性位点，且anatase相TiO2(101)表面的固氮活性最高。在对Fe掺杂的作用的研究中，本项目系统的研究了anatase相和rutile相TiO2不同表面共24种不同类型的Fe位点固氮活性，发现Fe位点并未展现出更高的催化活性，因此在实验中Fe可能通过间接方式提高TiO2固氮性能。最后，本项目筛选了过渡金属掺杂的anatase相TiO2。揭示了每种元素的掺杂位点，发现掺杂可以促进氧空位的形成。通过标度关系的分析，得到反应活性火山图并筛选出了若干个过渡金属掺杂的高效固氮的TiO2的催化剂。本项目的研究成果，有助于解释现有的实验现象，并为设计更高效TiO2基固氮催化剂提供理论指导。

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