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

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.