量子点敏化金属有机配合物间的电荷传递动力学及光催化CO2还原研究

One of key reasons for restrained photocatalytic efficiency is that most systems suffer from inefficient coupling of single-photon/electron events with multielectron redox reactions necessary for hydrocarbons generation from CO2 and hydrogen from water. Quantum dots (QDs) have broad solar absorption range, well stability, simultaneously absorb multiple photons, and can link catalysts directly onto the surface via appropriate functional groups. These characteristics make QDs superb candidates to fulfill multiple functionalities required in solar fuel generation as photosensitizers, electron/hole accumulation sites, and electron donors when they are properly coupled to efficient catalysts for CO2 reduction and H2 generation. Herein we have anchored the noble metal free complexes catalyst molecules to the surface of QD. According to the different elecronic transition energy, nanosecond, picosecond and femtosecond transient absorption measurements will be performed to study the transfer and conversion of the photoexcited photon, exciton, electron and ionic for complexes photocatalyst, reveal the mechanism of charge transfer, clearly display the photodriven charge separation dynamics, confirm the influence condition of charge transfer, consequently control and tune back electron transfer, and effectively enhance the photocatalytic CO2 reduction efficiency and understand the photocatalytic mechanism. On the basis of time-dependent density functional theory (TD-DFT) calculation and electrochemical properties, we will estimate the Gibbs free energy change ΔG for the electron transfer from the excited QDs to noble metal free complexes and the energy difference between the bond unite method in complexes catalytst, which makes the multistep photoinduced energy transfer thermodynamically possible for CO2 reduction in this catalyst system. The DFT calculation combined with the obtained results of photophysical properties measurements and the photocatalytic CO2 reduction will display clearly what playing for an important role for charge transfer. The project will bring further insight to the catalytsts design and their tuning for photoinduced electron transfer.

制约大多数体系光催化效率的主要原因之一是低效的单光子/电子与光催化二氧化碳还原或产氢过程所需的多电子氧化还原反应间存在供需关系的矛盾。本项目旨在利用量子点具有高吸光、稳定性高、多光子吸收，可分别作为光敏剂、电子/空穴聚集体、电子供给体等优点，合成量子点敏化非贵金属（钴、镍等）有机配合物催化剂。利用飞秒或皮秒超快光谱技术研究复合物催化剂在光激发过程中光子、激子、电子与离子的传递与转化的复杂理化过程，揭示电子空穴传递过程的机理，研究清楚电子和空穴传递的动力学过程，确定光催化过程中电荷传递的影响因素，从而达到调控电荷回传反应，有效提高光催化CO2还原效率和清楚展示光催化机理的目的。并通过含时密度泛函理论（DFT），估算电子从量子点导带位置传递到金属有机配合物中金属发生还原反应的吉布斯自由能及不同键联方式的催化剂形成中间活性体的能量差异，结合催化的具体效果实现理论与实际催化效果的结合。

制约大多数体系光催化效率的主要原因之一是低效的单光子/电子与光催化二氧化碳还原或产氢过程所需的多电子氧化还原反应间存在供需关系的矛盾。本项目在利用量子点具有高吸光、稳定性高、多光子吸收，可分别作为光敏剂、电子/空穴聚集体、电子供给体等优点，合成量子点敏化非贵金属（钴、镍等）非贵金属催化剂。系统研究了非贵金属催化剂粒子大小对光催化活性的影响，利用荧光淬灭、光电化学等手段揭示电子空穴传递过程的机理，研究清楚电子和空穴传递的动力学过程，确定光催化过程中电荷传递的影响因素，从而达到调控电荷回传反应，有效提高光催化活性和清楚展示光催化机理的目的。通过含时密度泛函理论（DFT）和瞬态光电流衰减曲线证实，催化剂不同晶面结构以及更长得瞬态衰减时间导致表面的电荷-空穴复合率下降，这将有效提高光催化活性。结合催化的具体效果实现理论与实际催化效果的结合。