Electrical conduction and reaction analysis on mixed-conducting iron-doped barium zirconate

Abstract

Mixed conducting BaZr0.9Fe0.1O3−δ perovskite (BZF10) was experimentally investigated in terms of electrochemical, catalytic and material characterization over a cycle of dry CO2, humidified Ar, CO and H2 for SOEC or SORFC operation. BZF10 exhibited both mixed ionic–electronic conduction under oxidizing conditions and mixed protonic–electronic conduction under humidified reducing conditions. Upon exposure to dry CO2 atm, the material shows catalytic activity towards CO2 reduction which is attributed to an intermediate carbonate ion formation on the cell surface. Exposure to moisture under inert gas environment suggests only mild interaction with steam; however, under moist CO environment a complex conduction mechanism is displayed alongside significant rates of water-gas-shift while exposure to humidified H2 indicates n-type semi-conduction. Upon completion of >1000h of continuous exposure to a range of oxidizing and reducing gas environments, physical inspection of the BZF10 electrochemical cell indicated negligible chemical or mechanical degradation, while XRD indicates retention of high perovskite phase purity with significant Fe segregation to the intergranular region confirmed via XEDS elemental mapping.