Reaction Rate Enhancement During the Electrocatalytic Synthesis of Ammonia in a BaZr_0.7Ce_0.2Y_0.1O_2.9 Solid Electrolyte Cell

The catalytic and electrocatalytic synthesis of ammonia was studied in a proton conducting double-chamber solid electrolyte cell. The BaZr_0.7Ce_0.2Y_0.1O_2.9 (BZCY72) proton conducting ceramic was used as the electrolyte with a Ni-BZCY72 cermet and a Pt film serving as cathodic and anodic electrodes, respectively. The reaction was studied at atmospheric pressure and at temperatures between 450 and 700 °C, under both, open- and closed-circuit conditions. A peculiar reaction rate enhancement was observed when the cell returned to open-circuit after operating under closed-circuit for a certain time. A possible explanation of this new phenomenon is that a fraction of protons electrochemically transported to the cathode, is “stored” in the Ni-BZCY72 electrode in the form of a highly reactive hydride which, upon current interruption, reacts with adsorbed N species to produce ammonia.