Homogeneous Solar Hydrogen Photocatalysis: Sensitizer Design and Mechanistic Insights from Transient Spectroscopy

在这个由化学部化学催化项目资助的项目中，北卡罗莱纳州立大学的Felix Castellano教授正在开发一种新的基于分子的产氢系统，该系统可以在光和水中发挥作用。虽然利用光将质子还原为氢分子的化学过程具有重要的基础技术意义，但只有少数基于分子的系统可以在纯水中完成这一重要的转化。该研究项目直接解决了与未来地球对可再生能源日益增长的需求和保护全球环境完整性相关的当前主题。参与该项目的学生正在接受化学多个领域的交叉训练。所建议的调查不仅促进了参与项目的本科生和研究生的科学和专业教育，而且还使这些学生参与区域公共科学教育推广活动。Castellano教授正在设计新的光敏剂，新型的电子供体，评估光催化循环激活途径（还原或氧化电子转移，三重态能量转移），并优化这些成分的组成，以发现使用瞬态光谱方法进行详细机制研究的最佳系统。正在合成的新型金属-配体电荷转移敏化剂是基于水溶性Ir(III), Ru（II）和Cu(I)配合物。利用三重态能量转移梭子介导初始电子转移反应到必要的钴基水还原催化剂和/或电子供体物质的概念也正在研究中。这些系统的性能指标正在使用组合光化学进行并行评估，并且正在使用各种分析方法来确定众多反应组分的化学命运并确定有害的分解途径。利用静态和动态光谱技术，对优化的光催化组合物的作用机制进行了详细的了解。这个跨学科项目为将太阳能转化为可再生的、环境友好的、非碳基化学燃料的基础知识基础做出了贡献。

In this project funded by the Chemical Catalysis Program of the Chemistry Division, Professor Felix Castellano at North Carolina State University is developing new molecular-based hydrogen-generating systems that function with light and in water. While the chemical process of using light to reduce protons to molecular hydrogen is of fundamental technological importance, only a handful of molecular-based systems can accomplish this important transformation in pure water. This research project directly addresses current themes related to the growing demand for renewable energy sources to power the planet in the future and safeguarding global environmental integrity. Students involved in this project are being cross-trained in numerous areas of chemistry. The proposed investigations are not only fostering the scientific and professional education of undergraduate and graduate students engaged in the project, but also are involving these students in regional public scientific education outreach activities. Professor Castellano is designing new photosensitizers, new classes of electron donors, evaluating the photocatalytic cycle activation pathways (reductive or oxidative electron transfer, triplet energy transfer), and optimizing the compositions of these components to discover the best systems for detailed mechanistic studies using transient spectroscopic methods. The new classes of metal-to-ligand charge transfer sensitizers being synthesizes are based upon water-soluble Ir(III), Ru(II), and Cu(I) complexes. The concept of employing triplet energy transfer shuttles to mediate the initial electron transfer reaction to the requisite cobalt-based water reduction catalyst and/or electron donor species is being studied as well. Performance metrics of these systems are being evaluated in parallel using combinatorial photochemistry, and various analytical approaches are being used to determine the chemical fate of the numerous reaction components and to identify deleterious decomposition pathways. A detailed understanding of the mechanisms of action of the optimized photocatalytic compositions is being gained using a battery of static and dynamic spectroscopic techniques. This interdisciplinary project is contributing to the fundamental knowledge base of converting solar energy into a renewable environmentally friendly, non-carbon-based chemical fuel.