Investigating Solid Electrolytes and Catalysts for Electrochemical Ammonia Synthesis
Ammonia (NH3) is a vital chemical to the agricultural and explosives industries, and it may very well play a central role in the emerging hydrogen economy. The Haber-Bosch process has long been the method used to synthesize ammonia from molecular nitrogen and hydrogen; however, it produces CO2 and consumes a significant amount of the global energy supply. This is due in part to molecular nitrogen’s strong triple bond, which makes it difficult to synthesize ammonia outside of extreme temperature and pressure conditions. With the goal of developing a sustainable method of producing ammonia, the focus has now shifted toward electrochemistry, which can facilitate the reduction of nitrogen under milder operating conditions. Presently, electrochemical techniques have not reached the necessary performance metrics to compete with the Haber-Bosch process, but continued improvements to the system and components may make it viable in the future. The purpose of this work is to synthesize and assess the performance of new catalysts and electrolytes in electrochemical devices for ammonia synthesis. These electrochemical devices are based on either a solid-state reactor operating under intermediate temperatures (300-600oC) and ambient pressure (1 atm) or an aqueous system operating in an ambient environment (25oC and 1 atm). For the solid-state systems, a proton conducting electrolyte (BaZr0.4Ce0.4Y0.1Yb0.1O3-x) and a sodium/potassium ion conducting electrolyte (β/β“-Al2O3) are both studied in a hydrogen-deficient mixture of N2 and H2. In the aqueous system, the performance of the working electrode, composed of ascorbic acid-treated VO2 with reduced graphene oxide (i.e. VO2 (A.A.) & RGO) and copper, is investigated.