This project focuses on a strategy for producing ammonia from N2 and H2O electrocatalytically at atmospheric pressure. The conventional route for ammonia (NH3) production is the Haber-Bosch (HB) process, which involves converting nitrogen and hydrogen through a thermo-catalytic reaction at high temperatures and high pressures. The demand for ammonia has been continuously increasing due to its widespread use in several industrial sectors including agriculture (approximately 80% of the produced ammonia is used to make fertilizer), transportation, pharmaceuticals, explosives, as well as the energy sector as a promising indirect hydrogen storage medium. Considering the increasing demand for NH3 and the highly energy-intensive nature of the conventional process with significant CO2 emissions, a cleaner and less energy-intensive alternative will have a significant economic and environmental impact. In addition, this project has the potential to provide new insights into the material synthesis and characterization, the mechanistic steps and the electro-catalytic phenomena, which can be translated to other catalytic and electrocatalytic systems for environmentally-important processes such as electrocatalytic reduction of NOx and CO2 electrolysis. Research activities proposed here will be integrated with established education and outreach programs at the Ohio State University with the ultimate goal of increasing student participation, retention and graduation in STEM fields.
The overall goal of the project is to develop highly active and selective cathode electro-catalysts for the high-temperature electrosynthesis of ammonia in solid oxide electrolysis cell (SOEC)-type reactors. The high-temperature (400-600 degrees C) electrocatalytic ammonia synthesis will involve dissociation of H2O to form H+ and O2- and the electrocatalytic activation of N2, followed by reaction with H+ to form NH3. In this scheme, O2- ions are conducted through the oxide ion conducting electrolyte to the anode, where they form molecular oxygen. In this study, we will examine a composite cathode system which is composed of perovskite oxides and metallic/bimetallic nitride/oxynitrides and we will investigate the synergy between these phases. The rationale of using a composite system is that the perovskite oxide phase will catalyze the H2O dissociation and provide oxide ion and electronic conductivity while the nitride/oxynitride phase will promote the N2 activation and provide nitrogen ion mobility. To the best of our knowledge, such a synergistic effect has never been reported before. Our approach to study the high-temperature electrocatalytic production of ammonia concept and to investigate an oxide/nitride composite cathode for this purpose will involve an iterative process of material synthesis, ex-situ/in-situ/operando characterization and electrocatalytic activity tests. The knowledge gained in this project will help open up a new route ammonia synthesis from N2 and H2O. It will also help develop similar electrolysis/electrocatalytic cells for environmentally-important processes such as electrocatalytic reduction of NOx and co-electrolysis of CO2 and H2O for syngas production. In addition to its potential contribution to the high-temperature electrocatalytic ammonia synthesis literature, the proposed study has significant potential to provide valuable insights in electrocatalysis, materials synthesis, surface chemistry and kinetics.
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.
