SusChEM: A Mechanistic Approach to Understanding and Lowering the Overpotential for CO2 Reduction to C1 Organic Products

美国国家科学基金会化学催化计划支持普林斯顿大学的安德鲁·B·博卡斯利教授研究二氧化碳(CO2)还原为一种碳(C1)有机产品的机制：甲酸、甲醛或甲醇。在甲醇的情况下，需要一个6电子、6质子的反应，该反应可以使用单电子氧化还原介体进行，或者在某些情况下可以观察到通过直接的二氧化碳-表面相互作用发生。在所有情况下，都牵涉到复杂的反应机制。研究小组研究了与甲酸盐形成相关的限速步骤(S)，甲酸盐是主要反应产物之一。过渡金属氧化物界面上的非均相二氧化碳还原，过渡金属分子体系的无界面二氧化碳还原，以及二氧化碳电还原的氰凝胶体系正在研究中。前两个主题探讨了反应表面在反应途径中的作用这一关键问题。为了在导致甲酸盐形成的动力学限制条件下考虑这个问题，研究小组检查了阳极化后过渡金属电极。这些材料在没有额外的溶解催化剂的情况下是催化的，使研究小组能够具体研究二氧化碳还原过程中直接发生在电极界面上的各种不同过程。这项研究是根据周期性趋势组织的，锌、镉、铟、铋和铅被选为关键体系。第二项研究从相反的方向攻击这个问题。在本研究中，芳香胺催化剂用于在没有表面的情况下进行二氧化碳的还原。在这里，利用光激Ru(联吡啶)体系的优势，电荷转移被芳香胺猝灭，在没有电极界面的情况下产生二氧化碳还原。在这方面，该小组还探索了含有双膦(L2)配体的锰络合物。最后一项研究使用氰凝胶化学，既产生有助于电极研究的合金材料，又产生已知具有高二氧化碳容量的新型电解液。了解二氧化碳的活化是一项关键的化学挑战，因为它有助于开发新的燃料资源，并有可能降低环境中的温室气体。除了它在下一代电化学研究人员的教育中的关键作用，他们是未来替代能源的关键，这个项目通过提供一个极好的工具来向学生和教师传授基本的化学概念，使用当前热门的温室气体控制问题作为激励原则，从而影响到K-12教育。拟议项目的另一个重要方面是它与一家积极进取的初创公司的密切联系，该公司专注于将这项研究从实验室带到现实世界。将二氧化碳转化为商业化学品的示范规模系统正在规划中。

The NSF Chemical Catalysis Program supports the efforts of Professor Andrew B. Bocarsly of Princeton University to investigate the mechanisms of carbon dioxide (CO2) reduction to one carbon (C1) organic products: formic acid, formaldedhyde or methanol. In the case of methanol, a 6-electron, 6-proton reaction is required which can be undertaken using either a one-electron redox mediator or in some cases can be observed to occur via a direct CO2-surface interaction. In all cases, a complex reaction mechanism is implicated. The research group examines the rate limiting step(s) associated with the formation of formate, one of the major reaction products. Heterogeneous CO2 reduction at post-transition metal oxide interfaces, interface-free CO2 reduction using transition metal based molecular systems, and cyanogel systems for CO2 electroreduction are under study. The first two topics explore the critical question of the role of a reactive surface in the reaction pathway. To consider this question under kinetically limiting conditions leading to formate formation, the team examines anodized post transition metal electrodes. These materials are catalytic in the absence of an additional dissolved catalyst, allowing the research group to look specifically at the range of heterogeneous processes occurring directly at the electrode interface during CO2 reduction. The study is organized using periodic trends, with zinc, cadmium, indium, bismuth and lead selected as key systems. The second study attacks the problem from the opposite direction. In this study, aromatic amine catalysts are used to carry-out the reduction of CO2 in the absence of a surface. Here, advantage is taken of the photoexcited ruthenium(bipyridyl) systems, charge transfer quenched by an aromatic amine to generate CO2 reduction absent an electrode interface. The team also explores manganese complexes containing bisphosphinine (L2) ligands, in this regard. The final study uses cyanogel chemistry to both generate alloy materials that will facilitate the electrode-based studies, and to produce novel electrolytes that are known to have a high CO2 capacity. Understanding CO2 activation is a critical chemical challenge as it contributes to the development of new fuel resources and as well as potentially lowering greenhouse gases in the environment. In addition to its pivotal role in the education of next generation electrochemical researchers, who are key to an alternate energy future, this program impacts K-12 education by providing an excellent tool for teaching both students and teachers fundamental chemical concepts using the currently topical problem of greenhouse gas control as a motivating principle. Another important aspect of the proposed program is its close affiliation with an aggressive startup company that is focused on taking this research out of the laboratory and into the real world. Demonstration scale systems that will convert CO2 into commercial chemicals are planned.