NSF-DFG: Strategies to Overcome Contemporary Limitations of Reductive Electrosynthetic Conversions in Aqueous Media

还原电合成是一种本质上绿色、安全和可持续的化学还原技术，因为它通过可再生风能/太阳能提供的电子取代了危险化学品和/或苛刻的反应条件。还原电合成还为提高转化效率和合成热化学或光化学无法获得的新分子提供了独特的机会。然而，该技术用于化学制造的实施受到寄生析氢反应和传统阴极材料的腐蚀的阻碍。该项目将引入高度颠覆性的概念，以解决这些严重的缺陷。这项工作是及时的，因为它将推动美国电力和化学制造业，并提供独特的推广和培训机会，建立一个植根于当地的干劳动力在中西部。寄生析氢反应（HER）和腐蚀的当代阴极材料将通过调查和开发两种创新的方法，即阳离子氢抑制剂和非常规金属和金属合金阴极材料。新型阳离子氢抑制剂将被设计为选择性地增加析氢反应的过电压，这将使得能够进行通过当前最先进的方法无法进行的反应。这些阳离子将与带负电荷的阴极相互作用并自组装以产生保护性离子层，该保护性离子层阻碍腐蚀和HER，同时实现电子到溶液中的基板的期望隧穿。将合成和研究具有各种分子结构的阳离子，以建立结构-性能关系。除了自组装，研究小组还将探索将选定的阳离子电接枝到合适的电极材料上。预期该方法赋予高灵活性，因为有机阳离子抑制剂可以进一步针对特定要求定制，例如使用手性添加剂将立体异构信息转移到所需底物。所述缺点也将从不同的角度通过设计非常规电极材料如Ga/In混合物、锌和铅的三元合金、铋和铋合金作为阴极来解决。预计这些材料在许多方面都将出类拔萃。例如，除了表现出高的氢过电位之外，与还原电化学中使用的现有金属电极相比，它们中的一些还应该表现出增加的生物相容性和对生物基腐蚀性化合物的耐受性。这种合金在水介质中还原电合成的性能尚未仔细研究，预计这样做将为有机电合成开辟新的途径。这两种方法的协同组合，即阳离子氢抑制剂和新型金属合金，也有望产生无与伦比的性能和耐久性，以应对挑战性的转变。本研究由NSF-DFG电合成和电催化牵头机构活动资助，通过本项目实现的技术进步将促进化学工业中绿色电化学的采用，并促进电化学制造过程的商业规模实施（NSF-DFG EChem）机会NSF 20- 578.该奖项反映了NSF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进行评估，被认为值得支持审查标准。

Reductive electrosynthesis is an inherently green, safe, and sustainable technology for chemical reductions as it replaces hazardous chemicals and/or harsh reaction conditions by electrons supplied by renewable wind/solar energy. Reductive electrosynthesis also offers unique opportunities for increasing conversion efficiencies and for synthesizing new molecules that are not accessible thermochemically or photochemically. However, the implementation of this technology for chemical manufacturing is hampered by the parasitic hydrogen evolution reaction and by the corrosion of conventional cathode materials. This project will introduce highly disruptive concepts that address these severe shortcomings. This effort is timely as it will advance the American power and chemical manufacturing industries, and provide unique outreach and training opportunities for building a locally-rooted STEM workforce in the Midwest.The parasitic hydrogen evolution reaction (HER) and corrosion of contemporary cathode materials will be addressed through the investigation and development of two innovative approaches, namely cationic hydrogen inhibitors and unconventional metal and metal alloy cathode materials. Novel cationic hydrogen inhibitors will be designed to selectively increase the overvoltage for the hydrogen evolution reaction, which will enable reactions that are inaccessible by the current state-of-the-art methods. These cations will interact with the negatively charged cathode and self-assemble to create a protective ionic layer that hampers corrosion and HER while enabling the desired tunneling of electrons to the substrates in solution. Cations with various molecular structures will be synthesized and investigated to establish structure-performance relationships. In addition to self-assembly, the research team will also explore the electrografting of selected cations to suitable electrode materials. This approach is expected to grant a high flexibility as the organic cationic inhibitors can be further tailored for specific requirements, for instance using chiral additives to transfer stereogenic information to desired substrates. The stated shortcomings will also be tackled from a different perspective by designing unconventional electrode materials such as Ga/In mixtures, ternary alloys of zinc and lead, bismuth, and bismuth alloys as cathodes. These materials are expected to excel in many aspects. For example, in addition to exhibiting high hydrogen overpotentials, some of them should also show increased biocompatibility and resistance to biobased corrosive compounds compared to existing metal electrodes used in reductive electrochemistry. The performance of such alloys for reductive electrosynthesis in aqueous media has not been carefully investigated yet and it is anticipated that doing so will open new avenues for organic electrosynthesis. The synergistic combination of both approaches, i.e. cationic hydrogen inhibitors and novel metal alloys, is also expected to yield unmatched performance and durability for challenging transformations. The technological advances achieved through this project will promote the adoption of green electrochemistry in the chemical industry and facilitate the implementation of electrochemical manufacturing processes at commercial scale.This research was funded under the NSF-DFG Lead Agency Activity in Electrosynthesis and Electrocatalysis (NSF-DFG EChem) opportunity NSF 20-578.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.