CAREER: Experimental Determination and Fundamental Theory of Mesoscopic Transport and Intrinsic Kinetics in CO2 Electrocatalysis

利用二氧化碳电解槽将二氧化碳(CO2)转化为燃料和化学品是在全球范围内推动化学制造业电气化和制造用于储能的合成燃料的一条很有前途的道路。以风能和太阳能产生的电子为动力的二氧化碳电解槽是实现零排放未来的关键技术。在所研究的用于二氧化碳电化学转化的各种金属中，铜是已知的唯一能有效催化多碳含氧物和碳氢化合物产生的单元素金属。关于铜如何催化这一转变，目前仍未达成共识。未来大型CO2电解槽的合理设计需要热力学和反应传递动力学方面的信息。本项目将解决铜催化剂体系反应-传输动力学信息不足的研究需求。该项目将把研究成果整合到加州大学洛杉矶分校的本科生和研究生培训中，同时还将协调与加州社区大学、少数族裔服务机构、国家实验室和行业的外联活动。教育和扩大影响的活动包括：i)为化学工程本科生开发为期两年的暑期研究经验。Ii)扩大与行业的联系，让不同的本科生和研究生参与研究研讨会和合作，以及iii)在本科生化学工程顶峰课程和PI教授的电化学工艺课程中介绍本提案中开发的电化学工程概念、细胞和理论。近年来，在确定CO_2电还原的反应机理和产物分布时，迁移与铜活性中心的本征催化动力学具有同等的地位，因此有必要在明确的质量、热量和电荷迁移条件下详细地提取反应动力学。这一基础工程研究项目解决了确定和建模与二氧化碳电催化相关的介观传输和反应动力学的迫切需要，包括：i)反应器设计和表征，ii)加速收集、摄取和情境化大型实验数据集，以使传输贡献与二氧化碳还原动力学脱钩，以及iii)多尺度反应-传输模型的开发和参数化。本文建立的反应-传输模型将是第一个用于电化学还原CO2的模型，并将为未来的CO2电解槽的合理设计和放大提供依据。这项研究将探索质量、热量和电荷传输如何决定二氧化碳还原过程中的产物选择性，并将开发建立铜电极上电催化过程的反应-传输模型所需的基本理论和工具。具有明确传输特性的电化学池将被用作工具来生成大型实验数据集，其中包括六个实验变量(外加电位、电池中的传输特性、电解液成分、温度、压力和催化剂孔隙率)与铜催化剂上16种不同液体和气体产品的产率之间的相关性。这一大型数据集将是高质量的，将用于确定铜电极上潜在的二氧化碳减少机制，以及外部和内部质量、热和电荷传输效应对在不同孔隙率的催化剂上观察到的不同产品分布的贡献。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。

The transformation of carbon dioxide (CO2) to fuels and chemicals using CO2 electrolyzers is a promising path forward for the electrification of the chemical manufacturing industry and the manufacturing of synthetic fuels for energy storage at a global scale. CO2 electrolyzers powered by electrons generated from wind and solar are key enabling technologies to achieve a zero-emissions future. Among the various metals studied for the electrochemical transformation of CO2, copper is the only single-element metal known to efficiently catalyze the production of multi-carbon oxygenates and hydrocarbons. There is still no consensus on how copper catalyzes this transformation. The rational design of future large-scale CO2 electrolyzers requires information on thermodynamics and reaction-transport kinetics. This project will address the research need of insufficient information on the reaction-transport kinetics on the copper catalyst system. This project will integrate results from research efforts into the training of undergraduate and graduate students at UCLA while also coordinating outreach activities to community colleges, minority serving institutions, national labs, and industries in California. The education and broadening impact activities include: i) development of a two year-summer research experience for chemical engineering undergraduate students. ii) outreach to industry and involvement of a diverse group of undergraduate and graduate students in research workshops and collaborations, and iii) introduction of electrochemical engineering concepts, cells, and theories developed in this proposal in the undergraduate chemical engineering capstone course, and the electrochemical processes course taught by the PI. Recently, it has become evident that transport is on equal footing with intrinsic catalytic kinetics of copper active sites in determining reaction mechanisms and product distributions of CO2 electroreductions, and thus a detailed extraction of reaction kinetics under well-defined mass, heat and charge transport conditions is necessary. This fundamental engineering research project addresses the critical need for the determination and modeling of mesoscopic transport and reaction kinetics relevant to CO2 electrocatalysis by combining: i) reactor design and characterization, ii) accelerated collection, ingestion, and contextualization of large experimental datasets to enable the decoupling of transport contributions from CO2 reduction kinetics, and iii) the development and parametrization of multi-scale reaction-transport models. The reaction-transport model developed here will be the first of its kind for electrochemical CO2 reduction and should enable the future rational design and scale-up of CO2 electrolyzers. The research will explore how mass, heat and charge transport determine product selectivity in CO2 reduction and will develop the fundamental theory and tools needed to build a reaction-transport model of electrocatalytic processes on copper electrodes. Electrochemical cells with well-defined transport properties will be utilized as tools to generate large experimental datasets of correlations between six experimental variables (applied potential, transport characteristics in the cell, electrolyte composition, temperature, pressure and catalyst porosity) and the production rates for 16 different liquid and gas products on copper catalysts. This large dataset will be of high quality and will be used to determine the underlying CO2 reduction mechanism on copper electrodes and the contribution of external and internal mass, heat and charge transport effects on the generation of different product distributions observed on catalysts with different porosities.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.