NSF-DFG Echem: Operando Electronic Structure Determination of Iron and its Time-Dependent Dynamics in FexNi100-x(OH)y Electrooxidation Catalysts

This project aims to identify the structure of iron within iron-nickel hydroxide catalyst materials. These materials are highly active electrocatalysts for key reactions important to next-generation energy conversion and storage, including water electrolysis to produce hydrogen and battery electrodes. Understanding the chemistry of the iron species underpins the overall goal of designing and synthesizing non-precious metal electrocatalysts to support our future energy economy. These electrocatalyst materials will also likely play a role in other future electrochemical technologies, including chemical conversion and upcycling, biomass conversion, water treatment, and resource recovery. As such, this project, and its pursuit of understanding how iron structure changes in the electrochemical environment, is critical to support national energy security, as well as to advance society toward clean energy technologies. Discoveries made will support a wide range of research activities focused on similar non-precious metal oxides and hydroxides, advancing not only the science of iron-nickel hydroxides but of other similar materials and of synchrotron-based spectroscopy techniques aimed at probing catalyst materials in their operating environments. This U.S.-German collaboration will also strengthen international scientific relationships and contribute to the development of a diverse, globally competitive science and engineering workforce.

The overarching research goal of this proposal is to experimentally probe Fe electronic structure under alkaline electrooxidation conditions by combining materials expertise with the x-ray spectroscopy instrumentation and expertise. Collaboratively conducted operando experiments will allow the team to unequivocally describe electronic state(s) of Fe and to understand the time dependency and hysteresis of Fe structural changes in FexNi100-x(OH)y nanocatalysts. The electrocatalytic reaction of focus will be the alkaline oxygen evolution reaction (OER). This project will further scientific understanding of the chemical and electronic structure of the active site for the OER in these catalysts, as well as advance fundamental understanding of Fe in the operando electrooxidative environment. The project will study a series of FexNi100-x(OH)y films and subsequently nanoparticle FexNi100-x(OH)y catalysts with soft x-ray absorption spectroscopy, x-ray emission spectroscopy, and resonant inelastic x-ray scattering. The project will focus on the iron L-edge and the oxygen K-edge of selected materials, and will include development of an operando cell for spectroscopy experiments, as well as detailed electrochemical analysis and in vacuo characterization of the catalyst materials.

This project was awarded through the 'NSF-DFG Lead Agency Activity in Electrosynthesis and Electrocatalysis (NSF-DFG EChem)' opportunity, a collaborative solicitation that involves the National Science Foundation and Deutsche Forschungsgemeinschaft (DFG).

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.