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

还原电合成是一种固有的绿色、安全和可持续的化学还原技术，因为它用可再生风能/太阳能提供的电子取代了危险化学品和/或恶劣的反应条件。还原电合成也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，寄生析氢反应和传统正极材料的腐蚀阻碍了该技术在化学制造中的实施。这个项目将引入高度颠覆性的概念，以解决这些严重的缺点。这一努力是及时的，因为它将促进美国电力和化学制造业的发展，并为在中西部建立本地的STEM劳动力提供独特的外展和培训机会。当代阴极材料的寄生析氢反应(HER)和腐蚀将通过研究和开发两种创新方法来解决，即阳离子氢抑制剂和非传统金属和金属合金阴极材料。新型阳离子氢抑制剂将被设计成选择性地增加析氢反应的过电压，这将使目前最先进的方法无法实现的反应成为可能。这些阳离子将与带负电荷的阴极相互作用并自组装，创建一层保护离子层，防止腐蚀和HER，同时使所需的电子在溶液中隧道传输到衬底。具有不同分子结构的阳离子将被合成和研究，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。这种方法有望提供高度的灵活性，因为有机阳离子抑制剂可以进一步为特定要求量身定做，例如使用手性添加剂将立体生成信息转移到所需的底物。还将从不同的角度解决所述的缺点，设计非传统电极材料，如Ga/In混合物、锌和铅的三元合金、铋和铋合金作为阴极。这些材料有望在许多方面脱颖而出。例如，与还原电化学中使用的现有金属电极相比，其中一些电极除了表现出高的氢过电位外，还应该表现出更好的生物兼容性和对生物基腐蚀性化合物的抵抗力。这类合金在水介质中的还原电合成性能尚未被仔细研究，预计这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，预计也将产生无与伦比的性能和耐久性，以应对具有挑战性的转变。通过该项目实现的技术进步将促进绿色电化学在化学工业中的采用，并促进电化学制造工艺的商业规模的实施。该研究由NSF-DFG领导机构电合成和电催化活动(NSF-DFG eChem)机会NSF 20-578资助。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.