Engineering Catalyst Materials for Carbon Utilization

化石燃料的燃烧产生二氧化碳--一种几乎没有商业价值的温室气体。催化电化学过程（电催化）提供了将二氧化碳升级为商业上重要的燃料或化学前体的机会。铜因其将二氧化碳（和一氧化碳）转化为含有几个碳原子的化合物的能力而成为电催化剂。该研究项目将建立在具有片状结构的铜纳米颗粒可以有效地促进一氧化碳与水的电催化反应以产生乙酸根离子的初步发现的基础上。这些研究的目的是改进合成铜纳米片颗粒的技术，并研究对催化剂的额外修改，以提高其将一氧化碳和二氧化碳转化为一系列有价值化学品的效率和选择性。将温室气体有效转化为有用的化学品将有助于解决我国面临的关键可持续性和环境挑战。该研究项目还将包括与特拉华州州立大学合作开展的教育和外联活动，这将扩大STEM中代表性不足的群体的参与，特别是女性和非洲裔美国学生。将二氧化碳升级为高价值的多碳（C2+）产品是可持续燃料和原料生产的一个有希望的途径。现有技术的二氧化碳电催化剂能够将二氧化碳转化为C1产物，例如一氧化碳和甲酸根离子，选择性大于80%。需要能够以可观的选择性将二氧化碳还原成更有价值的多碳化学品的电催化剂。在所有金属中，铜由于其产生广泛的C2+化学品的独特能力而在该应用中吸引了最多的关注;然而，此类反应的选择性较差。 为了改善铜的催化性能，人们进行了许多尝试来控制铜催化剂的形态和结构。 尽管如此，挑战仍然存在，制备选择性暴露特定面的高质量铜纳米材料在技术上具有挑战性。在初步研究中，研究小组成功合成了独立的三角形（111）暴露铜纳米片，这些材料能够将一氧化碳电化学转化为醋酸根离子，法拉第效率约为48%。 观察到的高乙酸酯选择性可能是由于铜（111）面在反应条件下促进乙酸酯形成的独特能力。该研究项目的目标包括三个主要方面：1）建立新的合成路线，获得高质量的铜（111）和铜（100）纳米材料; 2）基于铜模型表面构建铜/金属氧化物界面和单原子位点，理解二氧化碳/一氧化碳还原反应机理，3）考察了所合成催化剂在电化学反应条件下的稳定性。这些努力的结果将（1）导致新的合成方法，可以产生具有明确暴露面的高质量铜纳米结构;（2）提供使用二氧化碳作为原料生产高价值多碳化学品的电化学方法;（3）推进对铜基电催化剂结构-性质关系的基本理解;（4）提供一种新的合成方法，以制备具有良好暴露面的高质量铜纳米结构。（4）获得铜催化的二氧化碳/一氧化碳还原反应的重要机理见解;和（5）证明了可以扩展到其它重要化学反应的催化剂设计策略，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审查进行评估，被认为值得支持的搜索.

Combustion of fossil fuels produces carbon dioxide - a greenhouse gas having little commercial value. Catalyzed electrochemical processes (electrocatalysis) offer an opportunity to upgrade carbon dioxide to commercially important fuels or chemical precursors. Copper stands out as an electrocatalyst for its ability to convert carbon dioxide (and carbon monoxide) into chemical compounds that contain several carbon atoms. This research project will build upon the preliminary discovery that copper nanoparticles having a sheet-like structures can efficiently promote the electrocatalytic reaction of carbon monoxide with water to produce acetate ions. The studies will aim to refine the technique for synthesizing copper nanosheet particles and investigate additional modifications to the catalysts to improve their efficiency and selectivity for converting carbon monoxide and carbon dioxide to a range of valuable chemicals. Efficient conversions of greenhouse gases to useful chemicals will help to address key sustainability and environmental challenges facing our nation. The research project will also include educational and outreach activities in collaboration with Delaware State University that will broaden the participation of underrepresented groups in STEM, especially female and African American students. Upgrading carbon dioxide to high-value multi-carbon (C2+) products is one promising avenue for sustainable fuel and feedstock production. Current state-of-the-art carbon dioxide electrocatalysts are able to convert carbon dioxide to C1 products, such as carbon monoxide and formate ions, with selectivities greater than 80%. There is a need for electrocatalysts that can reduce carbon dioxide to more valuable multi-carbon chemicals with appreciable selectivity. Among all the metals, copper attracts most attention for this application due to its unique capability to produce a wide range of C2+ chemicals; however, such reactions suffer from poor selectivity. In order to improve catalytic properties of copper, numerous attempts have been made to control the morphology and structure of copper catalysts. Still the challenge remains that it is technically challenging to prepare high-quality copper nanomaterials that selectively expose specific facet(s). In preliminary studies, the research team has successfully synthesized freestanding triangular (111)-exposing copper nanosheets, and these materials are able to electrochemically convert carbon monoxide into acetate ions with a Faradaic efficiency of approximately 48%. The high observed acetate selectivity is presumably due to the unique capability of the copper(111) facet to promote acetate formation under the reaction conditions. The objectives of this research project encompass three main thrusts: 1) establish a new synthetic route to obtain high-quality copper(111) and copper(100) nanoscale materials, 2) construct copper / metal oxide interfaces and single-atom sites based on the copper model surfaces to understand carbon dioxide / carbon monoxide reduction reaction mechanisms, and 3) investigate the stability of the synthesized catalysts under electrochemical reaction conditions. The outcomes of these efforts will (1) lead to new synthetic methods that can produce high-quality copper nanostructures with well-defined exposed facets; (2) provide an electrochemical approach to produce high-value multi-carbon chemicals using carbon dioxide as the feedstock; (3) advance fundamental understandings of structure-property relationships in copper-based electrocatalysts; (4) gain important mechanistic insights into copper-catalyzed carbon dioxide / carbon monoxide reduction reactions; and (5) demonstrate a catalyst design strategy that might be extended to other important chemical reactions, such as dinitrogen reduction to ammonia and methane partial oxidation.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.