NH3 is a critical global resource for fertilizers and chemical intermediates and can also serve as an easily transported hydrogen vector in support of a green hydrogen economy. An electrochemically driven process generates high chemical potential of reactant species allowing us to circumvent pressurization of the system. Thus, electrochemical NH3 synthesis would reduce capital costs, decrease energy consumption, and enable NH3 synthesis at smaller scales than the incumbent high-pressure approach (the Haber-Bosch process). In this work, we electrochemically synthesized ammonia (NH3) using protons, steam (H2O), and N2 as reactants over molybdenum oxynitride using cesium dihydrogen phosphate (CsH2PO4) solid acid as the electrolyte (38% H2O, 62% N2 at cathode, 38% H2O, 62% H2 at anode, at 1 atm total pressure, 250°C, and -0.7 VOCV). We first discuss the challenge of eliminating false NH3 positives and protocols to confidently quantify NH3 using NMR. Molybdenum oxynitrides were synthesized from molybdenum trioxide (MoO3) precursors and utilized in the cathode. We find that NH3 is only produced at the cathode (no NH3 is produced from the anode) and that increased hydrogen pressure (H2) suppresses the NH3 synthesis rate.

Thermal-electro-catalytic production of ammonia (NH3) over molybdenium oxynitride at 250°C using cesium dihydrogen phosphate (CsH2PO4) solid acid electrolytes

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