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

在这个由化学系化学催化计划资助的项目中，北卡罗来纳州州立大学的Felix Castellano教授正在开发新的基于分子的氢生成系统，该系统在水中和光中发挥作用。虽然利用光将质子还原为分子氢的化学过程具有基本的技术重要性，但只有少数基于分子的系统可以在纯水中完成这一重要转变。该研究项目直接涉及与可再生能源需求不断增长有关的当前主题，以在未来为地球提供动力，并维护全球环境完整性。参与该项目的学生正在化学的许多领域进行交叉培训。拟议的调查不仅促进参与该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外联活动。 Castellano教授正在设计新的光敏剂，新的电子供体类别，评估光催化循环活化途径（还原或氧化电子转移，三重态能量转移），并优化这些组分的组成，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基于水溶性Ir（III）、Ru（II）和Cu（I）络合物。 采用三重态能量转移梭来介导初始电子转移反应至所需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并行评估，各种分析方法被用来确定众多的反应组分的化学命运，并确定有害的分解途径。使用一系列静态和动态光谱技术，可以详细了解优化的光催化组合物的作用机制。这一跨学科项目有助于将太阳能转化为可再生的环境友好型非碳基化学燃料的基本知识基础。

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.