Pulsed Electrolysis for Enhanced Nitrate Reduction Reaction to Ammonia at Low Concentrations

Electrochemical nitrate (NO3 -) reduction reaction (NO3 -RR) could offer a transformative pathway to generate ammonia in a sustainable, electrified, and decentralized manner. Improving the selectivity of the electrochemical process toward desired products and minimizing competing reactions (e.g., hydrogen evolution reaction) are the major bottlenecks before widespread adoption of the technology at an industrial scale. In this talk, we present our recent efforts in leveraging various electrochemical techniques, including pulsed electrolysis, to enhance the selectivity of the process toward ammonia at low nitrate concentrations (e.g., 10 mM). We use computational and experimental techniques to pinpoint the mechanism for the improved performance of nitrate reduction reaction to ammonia under pulse electrolysis in flow-cell electrochemical systems. We characterize the catalysts and local microenvironment under pulsed electrolysis and potentiostatic conditions to understand their impacts on ammonia yield and energy efficiency of the electrochemical process. This work provides foundational knowledge and understanding of materials and processes to demonstrate electrochemical NO3 -RR to ammonia at low nitrate concentrations, enabling a paradigm shift toward green and sustainable fuel synthesis from nitrogen source and water under more realistic nitrate concentrations in various wastewater sources.