Ammonia Synthesis by N2and Steam Electrolysis in Solid-State Cells at 220°C and Atmospheric Pressure

Ammonia was synthesized directly from N 2 and steam using electrolytic cells based on CsH 5 (PO 4 ) 2 /SiO 2 composite electrolytes and Pt-based electrodes. Steam was electrolyzed at the anode to produce protons and oxygen. The protons moved through the electrolyte to the cathode, and combined with nitrogen and electrons to produce ammonia. Ammonia was synthesized under 1.2–1.6 volts of applied voltage at 220°C and atmospheric pressure. When the applied voltage was 1.2 V, the electrolytic cell employing Pt/C-loaded carbon paper as both electrodes produced ammonia at a formation rate of 2.0 × 10 −10 mol cm −2 s −1 and faradaic efficiency of 2.1%, where the area is the geometric surface of the electrode. With the increase of the applied voltage, both the ammonia formation rate and faradaic efficiency decreased rapidly. This novel process fills the temperature gap in the field of solid-state electrochemical synthesis of ammonia as previous studies were conducted either below 100°C (polymer electrolytes) or above 375°C (ceramics or composite electrolytes).