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推动化学反应，包括从水中产生氢气。氢可以进一步与其他分子反应，产生比电能更容易储存和运输的化学燃料。海水是一种丰富的水资源，但从海水中电化学制氢会从海水盐类中产生有害的副产品，造成环境和安全问题。该项目将设计和测试材料和电化学反应条件，以选择性地促进氢气的产生，同时避免产生不受欢迎的含氯副产品。科学成果将有助于制定改进的能源储存和化学制造战略，以减少我国对不可再生资源的依赖。此外，这项研究将与强调代表人数不足的群体参与的教育和推广举措相结合。该项目的重点是在含氯盐的系统中选择性电催化水氧化。通过操纵氧化物催化剂的电子结构，当在高共价材料中引发依赖于pH的氧氧化还原活化时，水和氯氧化过程的活性中心将被解耦。这避开了过渡金属位置上含氯和含氧中间体的结合强度之间的耦合，阻碍了反应路径的独立优化。原位和操作面光谱方法(X射线、振动)将识别吸附物种、它们对外加电势和电解液组成的依赖以及它们与共吸附物质的相互作用。吸附亲和力与理论计算的比较将建立作为表面能函数的所需反应路径的折衷。此外，这项研究将从机理上理解电催化剂上的二次锰氧化物涂层在限制氯离子的传输和操纵埋藏界面上的吸附结合方面所起的作用。将制定涂层的设计参数，使其能够以最低的催化活性成本在盐水中进行选择性氧化。拟议工作的结果将被纳入本科反应工程课程和K-12 STEM推广计划，旨在向学生传授电化学系统。同行教学将被用来巩固对科学和工程技能的理解和增加信心，特别是在STEM中代表性较低的群体。该项目由化学、生物工程、环境和运输系统部门的催化计划以及材料研究部门的固体和材料化学计划联合支持。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。

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.