La0.6Sr0.2Co0.2Fe0.8O3-δ　(LSCF)　is　the　most　intensively　investigated　high　performance　cathode　for　intermediate　temperature　solid　oxide　fuel　cells　(IT-SOFCs),　but　strontium　segregation　and　migration　at　the　electrode/electrolyte　interface　is　a　critical　issue　limiting　the　electrocatalytic　activity　and　stability　of　LSCF　based　cathodes.　Herein,　we　report　a　Nb　and　Pd　co-doped　LSCF　(La0.57Sr0.38Co0.19Fe0.665Nb0.095Pd0.05O3-δ,　LSCFNPd)　perovskite　as　stable　and　active　cathode　on　a　barrier-layer-free　anode-supported　yttria-stabilized　zirconia　(YSZ)　electrolyte　cell　using　direct　assembly　method　without　pre-sintering　at　high　temperatures.　The　cell　exhibits　a　peak　power　density　of　1.3　W　cm−2　at　750　°C　and　excellent　stability　with　no　degradation　during　polarization　at　500　mA　cm−2　and　750　°C　for　175　h.　Microscopic　and　spectroscopic　analysis　show　that　the　electrochemical　polarization　promotes　the　formation　of　electrode/electrolyte　interface　in　operando　and　exsolution　of　Pd/PdO　nanoparticles.　The　Nb　doping　in　the　B-site　of　LSCF　significantly　reduces　the　Sr　surface　segregation,　enhancing　the　stability　of　the　cathode,　while　the　exsoluted　Pd/PdO　nanoparticles　increases　the　electrocatalytic　activity　for　the　oxygen　reduction　reaction.　The　present　study　opens　up　a　new　route　for　the　development　of　cobaltite-based　perovskite　cathodes　with　high　activity　and　stability　for　barrier-layer-free　YSZ　electrolyte　based　IT-SOFCs.　©　2017　Elsevier　B.V.