CAREER: Tailoring the Selectivity of Electrocatalytic Reactions in Seawater and Brine

来自风能、太阳能、波浪和潮汐等能源的可再生电力可用于驱动化学反应，包括从水中产生氢气。氢气可以进一步与其他分子反应，产生化学燃料，与电能相比，化学燃料更容易储存和运输。海水是丰富的水资源，但电化学制氢会产生有害的海水盐副产物，对环境和安全构成威胁。该项目将设计和测试材料和电化学反应条件，选择性地促进氢的产生，同时避免产生不需要的含氯副产物。科学成果将有助于改进能源储存和化学制造战略的发展，从而减少我们国家对不可再生资源的依赖。此外，这项研究将与强调代表性不足群体参与的教育和外联倡议结合起来。该项目侧重于含氯盐系统中的选择性电催化水氧化。通过操纵氧化物催化剂的电子结构，当在高共价材料中触发ph依赖的氧氧化还原激活时，水和氯氧化过程的活性位点将解耦。这避开了氯和含氧中间体在过渡金属位点的结合强度之间的耦合，阻碍了反应途径的独立优化。原位和操作光谱方法（x射线，振动）将识别吸附物质，它们对应用电位和电解质组成的依赖，以及它们与共吸附物的相互作用。吸附质亲和性与理论计算的比较将建立一个权衡所需的反应途径作为表面能量的函数。此外，该研究将对电催化剂上的二次氧化锰涂层在限制氯离子的传输和控制埋藏界面上吸附质的结合方面所起的作用产生机理上的理解。设计参数将开发涂层，使其能够在盐水中选择性氧化，并以最小的成本降低催化活性。研究结果将被纳入本科反应工程课程和旨在教授学生电化学系统的K-12 STEM外展计划。将采用同伴教学来巩固对科学和工程技能的理解，增强对科学和工程技能的信心，特别是在STEM中代表性不足的群体中。该项目由化学、生物工程、环境和运输系统部门的催化项目和材料研究部门的固态和材料化学项目共同支持。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Renewable electricity from energy sources such as wind, solar, wave, and tidal can be used to drive chemical reactions, including the generation of hydrogen from water. The hydrogen can be further reacted with other molecules to produce chemical fuels that are more easily stored and transported compared to electrical energy. Seawater is an abundant water resource, but electrochemical hydrogen generation from seawater can generate harmful byproducts from seawater salts that pose environmental and safety concerns. The project will design and test materials and electrochemical reaction conditions that selectively promote hydrogen generation while avoiding the production of undesirable chloride-containing byproducts. The scientific outcomes will aid the development of improved energy storage and chemical manufacturing strategies that reduce our nation’s reliance on non-renewable resources. Furthermore, the research will be integrated with educational and outreach initiatives emphasizing participation by underrepresented groups.The project focuses on selective electrocatalytic water oxidation in systems containing chlorine salts. By manipulating the electronic structure of an oxide catalyst, the active sites for water and chlorine-oxidation processes will be decoupled when the pH-dependent activation of oxygen redox is triggered in highly covalent materials. This sidesteps the coupling between binding strengths of chlorine- and oxygen-containing intermediates at transition metal sites, hindering independent optimization of the reaction pathways. In situ and operando spectroscopic approaches (X-ray, vibrational) will identify adsorbed species, their dependence on applied potential and electrolyte composition, and their interaction with co-adsorbates. Comparison of adsorbate affinity with theoretical calculations will establish a tradeoff in desired reaction pathway as a function of surface energetics. Furthermore, the study will generate mechanistic understanding of the role a secondary manganese-oxide based coating atop an electrocatalyst can play in limiting the transport of chloride ions and manipulating adsorbate binding at the buried interface. Design parameters will be developed for the coatings that enable selective oxidation in brines with minimal cost to catalytic activity. The findings of the proposed work will be incorporated into undergraduate reaction engineering courses and K-12 STEM outreach programs designed to teach students about electrochemical systems. Peer teaching will be employed to solidify understanding and increase confidence in science and engineering skillsets, particularly in groups typically underrepresented in STEM.The project is supported jointly by the Catalysis program in the Division of Chemical, Bioengineering, Environmental and Transport Systems, and the Solid State and Materials Chemistry program in the Division of Materials Research.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.