Doped Barium Niobate Perovskite Based Materials for High-Temperature Electrolyzer Application and Efficient Methane Conversion

Abstract

Perovskite materials have helped make notable advances in many applications over the last few decades. Specifically, in high temperature electrochemical technologies such as solid oxide fuel cells (SOFC) and electrolyzers where perovskite-based electrolyte and electrode materials are playing pivotal roles. However, high temperature operation poses significant challenges in both fabrication and durable operation that is further complicated by the operating environment. For example, an electrolyte in a SOFC faces a highly oxidizing environment on the cathode while highly reducing environment on the anode and hence should possess chemical stability under these operating conditions and lifetime requirements for energy conversion technologies often times exceed 10 years of usage with no more than 20% degradation.[1]. Electrochemical oxidative coupling of methane (E-OCM) to ethylene process faces further problems associated with coke and carbonate formation along with the over oxidation of CH4 that invariably leads to CO and CO2. Here we present exciting class of barium niobate perovskites where different cations such as Mg, Ca, Y, and Fe on the niobium site was used for doping and evaluated for E-OCM application. The results are compared with another perovskite material Sr2Fe1.5Mo0.5O6- d (SFMO) that showed good catalytic activity but poor chemical stability. [2][3] Prepared perovskite material was analyzed by XPS, TGA, TPR, SEM, and TEM methodologies towards their chemical stability. Electrochemical properties were evaluated in a home-made setup using different electrolyte materials in the temperature range of 700°C to 900°C by methods such as cyclic voltammetry, impedance spectroscopy, and chronoamperometry. Electrochemical measurements coupled with continuous mass spectra analysis provided valuable insights between product distribution and applied potential. Our results demonstrate doped barium niobates as a promising candidate for stable operation in high temperature electrochemical applications.