Area-specific resistances Barium compounds Cathodes Cerium compounds Electrochemical performance Energy conservation Environmental technology Intermediate temperatures Lanthanum compounds Proton-conducting solid oxide fuel cells Sol-gels Solid oxide fuel cells (SOFC) Strontium compounds Zirconium compounds Activated carbon Activation energy Additives Chemical additive Electrical conductivity Electrocatalytic activity Electrochemical impedance spectroscopy Electrode material Electrolytes Ethylene Ethylene glycol Film thickness High temperature operations Porosity Proton conducting Proton-conducting electrolyte