Electrochemical Cycling Process for Ammonia Synthesis Using N2 and H2o at Atmospheric Pressure

Monday, 2 October 2017: 08:00
National Harbor 5 (Gaylord National Resort and Convention Center)
J. M. McEnaney (Stanford University Department of Chemical Engineering), A. R. Singh, J. Schwalbe (Stanford University), J. Kibsgaard (Stanford University Department of Chemical Engineering), J. C. Lin, M. Cargnello, T. F. Jaramillo, and J. Nørskov (Stanford University)
Conventional ammonia synthesis via the Haber Bosch process facilitates fertilizer production to sustain the massive and growing human population. The massive scale of ammonia production of consumes over 1% of the entire global energy supply and releases ~450 million metric tons of CO2 into the atmosphere each year due to its dependence on fossil fuels for H2 production. In this work, we demonstrate a generalized alternative pathway toward sustainable ammonia synthesis via an electrochemical cycling strategy. This electrification strategy is amenable to be powered by renewable energy and to be locally implemented where the ammonia fertilizer needed by circumventing the high pressure and H2 gas requirements of the Haber Bosch process and instead using electricity and H2O. The process can be summarized by three distinct steps of surface preparation, nitrogen activation, and ammonia synthesis which can be combined and cycled for continuous ammonia production. The feasibility and general applicability of this cycle were evaluated with theoretical analyses. The process steps are characterized with specific electrochemical and materials chemistry techniques. Ammonia is quantified by UV-Visible colorimetric analysis and confirmed to be from N2 via isotopic labeling in Fourier transform infrared radiation studies. We experimentally demonstrate an initial current efficiency of 88.5% toward ammonia production via this process and we begin to evaluate the potential of this strategy for viability.