(292b) Calcium Mediated Electrochemical Synthesis of Ammonia

The synthesis of green ammonia will be a steppingstone toward a sustainable and safe future. It not only finds applications as an agricultural fertilizer but is also being explored in energy storage domains. To sustainably utilize ammonia in these applications, alternate processes are required which can alleviate the massive carbon footprint and energy utilization, unlike the conventional Haber-Bosch process. Electrochemical synthesis of ammonia helps to make the process green by consuming renewable resources for electricity consumption. The proposed work aims to study electrochemical calcium-mediated ammonia synthesis (Ca-MAS). The reaction proceeds with the electrodeposition of calcium metal on the different substrates which subsequently undergoes nitridation and then finally leads to the formation of ammonia. Li-mediated synthesis of ammonia has been explored greatly by varying various parameters and enhancing performance but since Li is very reactive it is limited by safety issues associated with it. Calcium is expected to demonstrate a superior performance since it has a lower equilibrium potential for deposition, unlike lithium, and will assist in obtaining better energy efficiencies. Moreover, it is 10,000 times more abundant than Lithium, therefore, economically lucrative. Various substrates for Ca deposition have been studied to optimize the system's performance. Copper coated on nickel mesh is identified as the most promising substrate. It has been inferred that the thickness of copper on different substrates plays a major role and optimum thickness is needed to balance the trade-off between very less availability of copper to form the nitride and too much copper to impede the dinitrogen transportation. 50nm has been identified as the optimum thickness for this case. Various electrolyte compositions are studied with varying base electrolytes such as THF, propylene carbonate, acetonitrile, and Dimethyl sulfoxide (DMSO) based on their volatility, conductivity, and stability and their effect on the performance in terms of FE and current densities have been analyzed. Achieving almost similar yields and current efficiencies as Lithium-mediated will significantly lower the costs associated with the entire process and make it even more benign.