Proton conduction in Ba_xCe_0.8Y_0.2O_3−α + 0.04ZnO at intermediate temperatures and its application in ammonia synthesis at atmospheric pressure

Abstract

Dense ceramic samples Ba_xCe_0.8Y_0.2O_3−α + 0.04ZnO (x = 1, 0.98, 0.96, 0.94) were successfully prepared by a solid-state reaction method, whose sintering temperature was about 573 K lower than a traditional solid state reaction method without sintering aid. XRD patterns indicated that all the samples exhibited a single-phase of orthorhombic perovskite structure. The conduction behavior was investigated by alternating current impedance in wet hydrogen atmosphere at 673–1073 K. It was found that the conductivities were affected by the nonstoichiometric amount of Ba, and increased in the order: σ (x = 0.94) < σ (x = 1) < σ (x = 0.96) < σ (x = 0.98). It was also found that the samples were almost pure ionic conductors and contributed mainly by proton and partially by oxide ion in wet hydrogen atmosphere at 773–1073 K. The ammonia synthesis at atmospheric pressure was successfully conducted using an electrolytic cell based on Ba_0.98Ce_0.8Y_0.2O_3−α + 0.04ZnO. The ammonia formation rate reached 2.36 × 10⁻⁹ mol s⁻¹ cm⁻² under the suitable conditions of 0.8 mA and 773 K.