The different formulations of solid-state materials, co-doped lanthanum-chromite (LSCrF) perovskite, and gadolinium-doped ceria (GDC) fluorite were prepared and used as electrocatalyst to enable the green production of ammonia via nitrogen and steam reaction at the cathode compartment. An optimized ball milling approach (defined as OBMA) was implemented to produce the cathodic composites to respond to the environmental stimuli changes of operational temperature and applied voltage. The solid oxide electrolysis cells (SOECs) were then assembled and used for ammonia production . The cathodic catalysts were found to maximize the efficacy of ammonia production due to the formation of oxygen vacancies, high interactivity between catalysts and reactants, and gas channeling by the macro-porous structure. To tune the macro-porous structure of the cathodic composites, the group invented an in-situ templating using a porogen (polymethylmethacrylate) with controllable size to facilitate gas diffusion and adsorption along with the interfaces of phase boundaries.

This OBMA synthesis and macro-porous structures resulted in an improved intrinsic electrocatalytic property of LSCrF-GDC based on the measurement of impedances. The formation rate of ammonia was found to be improved when the SOEC technology was implemented under an applied voltage of 1.8 V and operating temperature at 600 °C. The mechanism study of electrochemical performance and interactivity between cathodic catalysts and reactants indicated that an optimized ammonia production pathway was carried out below thermoneutral enthalpy at high efficiency (the ratio between the enthalpy flow of produced hydrogen and the electrical power input). The contribution of this study lies in the optimized methodology to enhance interactive electrocatalysis applied for green synthesis of ammonia.

Green Catalytic Synthesis of Ammonia using Solid Oxide Electrolysis Cells Composed of Multicomponent Materials

Qiang Zhen

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