Hybrid catalyst system combining hot electron-generating quantum dots and molecular catalyst for efficient photocatalytic CO2 reduction

光催化利用来自太阳的能量来实现从低价值或对环境有害的分子中生产高价值燃料和化学品的可持续途径。在这个项目中，将研究光催化剂的新组合，以将二氧化碳（CO2）升级为可用于制造燃料或化学品的分子。新的催化材料将有助于为国家未来的能源安全铺平道路，同时减少碳排放对环境的影响。该项目还包括各级教育和推广计划，从培训研究生和本科生能源相关技术到提高K-12学生对stem相关领域的兴趣。所提出的混合系统的新颖性在于将特定掺杂量子点（QD）光敏剂与分子过渡金属基催化剂相结合。掺杂量子点在辐照时产生热电子的能力将允许远程热电子光敏化和有效的电子转移到分子CO2还原催化剂，而不需要在敏化剂和催化剂之间直接连接。在新的混合系统中，锰和铜双掺杂量子点将在弱可见光下产生高能热电子，这将对溶液中的分子催化剂进行有效的远程（例如10 nm）敏化。增感体积的大幅增加和向分子催化剂能量上更有利的单向热电子转移，有望提高杂化催化剂体系的整体催化CO2还原效率，同时保持非偶联杂化催化剂体系在构建和再生方面的便利性和灵活性。为了量化整个光催化还原过程中每个阶段的关键过程的速率，并通过敏化剂和混合系统的结构变化来优化其效率，将追求以下几个目标：(1)对掺杂量子点敏化剂进行结构控制，以获得最大的热电子生成效率；(2)对分子铼基和镍基分子催化剂的热电子敏化效率进行定量测量；(3)对反应器在不同反应条件下的整体催化效率进行评估。将本文设计的杂化催化剂与现有杂化结构的整体效率进行比较评估，将有助于确定热电子敏化杂化催化剂体系的最佳结构。在教育方面，新的多媒体材料将用于补充本科实验室和研究生班以及关于仪器/数据获取/处理的讲习班的仪器训练。拓展将包括与等离子体纳米晶体合成有关的新的动手实验和简单的光学实验，这些实验可以由初中或高中班级安全地进行，作为他们科学课程的一部分。此外，德州范围内的德州大小水晶大赛正在组织中，这将使大量的高中学生和教师体验晶体固体的迷人世界。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Photocatalysis utilizes energy from the sun to achieve a sustainable route to producing high-value fuels and chemicals from low-value or environmentally harmful molecules. In this project, new combinations of photocatalysts will be investigated to upgrade carbon dioxide (CO2) to molecules that can be used to make fuels or chemicals. The new catalytic materials will help pave a path to the Nation's future energy security while decreasing the environmental impact of carbon emissions. The project also includes plans for education and outreach at all levels, ranging from training graduate and undergraduate students in energy-related technologies to promoting interest in STEM-related areas amongst K-12 students.The novelty of the proposed hybrid systems lies in the combination of specifically doped quantum dot (QD) photosensitizers with molecular, transition metal-based catalysts. The ability of doped QDs to generate hot electrons upon irradiation will allow for long-range hot electron photosensitization and efficient electron transfer to molecular CO2 reduction catalysts without the need for direct linkage between the sensitizer and catalyst. In the new hybrid systems, manganese and copper dual-doped quantum dots will produce energetic hot electrons under weak visible light, which will perform efficient long-range (e.g., 10 nm) sensitization to molecular catalysts in solution. The large increase of the sensitization volume and energetically more favorable and unidirectional hot electron transfer to the molecular catalyst are expected to enhance the overall catalytic CO2 reduction efficiency of the hybrid catalyst system, while keeping the convenience and flexibility of uncoupled hybrid catalyst system in construction and regeneration. To quantify the rates of key processes at each stage of the entire photocatalytic reduction process and to optimize their efficiency through structural variations of the sensitizer and hybrid system, several objectives will be pursued: (1) structural control of the doped quantum dot sensitizer for maximum hot electron generation efficiency, (2) quantitative measurements of hot electron sensitization efficiency to molecular rhenium- and nickel-based molecular catalysts, and (3) assessment of the overall catalytic efficiency in the reactor at varying reaction conditions. Comparative evaluation of the overall efficiency of the hybrid catalysts designed here with that of the existing hybrid architectures will lead to the identification of the optimum structure of the hot electron-sensitized hybrid catalyst system. With respect to education, new multimedia materials will be used to complement instrumental training in undergraduate laboratories and graduate classes and in workshops on instrumentation/data acquisition/processing. Outreach will involve new hands-on experiments that are related to the synthesis of plasmonic nanocrystals and simple optical experiments that can be safely performed by middle or high school classes as a part of their science curriculum. Additionally, the Texas-wide Texas Sized Crystal Contest is being organized which will allow large numbers of high school students and teachers to experience the fascinating world of crystalline solids.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.