Bottom-up design of earth-abundant catalysts for reversible hydrogen oxidation and reduction in alkaline electrolytes

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Hydrogen is a critical feedstock for industrial chemistry and a potential low-cost medium for renewable energy storage. Both the hydrogen oxidation (HOR) and evolution (HER) reactions are extremely fast on platinum and other catalysts in acidic electrolytes, but sluggish in alkaline electrolytes. The research aims to identify the reasons for the adverse effects of alkaline pH on hydrogen electrocatalysis and use the resulting insight to design active HER/HOR electrocatalysts from earth-abundant materials, thereby enabling broader utilization of low-cost fuel cell and electrolyzer technologies. The work will support graduate and undergraduate education, and outreach to high school students, all directed toward broader understanding and appreciation of opportunities for electrochemistry to contribute to sustainable methods for the production of energy and chemicals.Study of the hydrogen electrode has long played a key role in the development of core concepts in electrochemistry and electrocatalysis. Hydrogen binding energy (HBE) is usually assumed to control reactivity, and the role of water in defining reaction kinetics and pathways is often overlooked. This study applies a unique suite of experimental techniques and theoretical analyses to isolate the effects of individual phenomena in alkaline hydrogen electrochemistry. Controllably strained, homogeneous surfaces will be used to investigate the effect of pH on HBE. Electrochemical quartz crystal microbalance and CO displacement measurements will be used to observe surface-adsorbed hydroxide, and the resulting information will be combined with conventional electrochemical experiments and microkinetic models to identify the role of hydroxide in the alkaline hydrogen reactions conducted on surface-doped catalysts. In addition, catalyst supports will be varied to determine the impact of water orientation. The fundamental insight gained will be used to synthesize active, stable electrocatalysts based on earth-abundant elements. Understanding the effects of pH on adsorption energy and activation barrier heights will provide important insight, not only for fuel cells and renewable energy storage, but for other economically and environmentally important electrochemical processes such as corrosion, carbon dioxide reduction, direct oxidation of fuels, flow batteries, ammonia synthesis and biological redox systems. The project will provide two PhD students and several undergraduate students with a broad and interdisciplinary research experience with training in electrochemical methods, surface science, and materials synthesis and characterization. In conjunction with the work, the PIs will develop electrochemistry-centered educational modules for Drexel University's Freshman Design course, including collaboration with a local high school's chapter of the Girls Who Code club.