Recent advances in protonconducting electrolytes for solid oxide fuel cells

The performance characteristics of solid oxide fuel cells operating at intermediate temperatures depend largely on the tailored properties of the electrolyte used in making these cells. The extensive properties like conductivity and stability have a direct correlation with the defect chemistry of the electrolyte material. Proton conductors are gaining momentum as plausible electrolytes for intermediate temperature solid oxide fuel cells (IT-SOFC). The replacement of electrolytes which conduct oxide ion (O\(^{2-}\)) by proton ion (H\(^{+}\)) largely enhances the performance in addition to decrease of cost of operation. But tailoring the oxide electrolytes for both high proton conductivity and chemical stability is a challenging task as they are antagonistic properties. This review discusses in detail the various electrolyte structures exhibiting proton conduction and also studies the effect of various dopants which alters the conductivity and stability of proton-conducting electrolytes for IT-SOFC. This review elaborates the mechanism of proton conduction in various oxides thereby providing a correlation between the structural and mechanistic features of the solid electrolytes. This review envisages to study the properties of proton-conducting electrolytes and aims to propose a framework that correlates the synthesis and properties of tailored electrolytes to the overall performance of the IT-SOFC for commercial applications.