Bismuth-based　oxides　exhibit　outstanding　oxygen　ionic　conductivity　and　fast　oxygen　surface　kinetics　and　have　shown　great　potential　as　a　highly　active　component　for　electrode　materials　in　solid　oxide　fuel　cells　(SOFCs).　Herein,　a　Nb-doped　La0.6Sr0.4Co0.2Fe0.7Nb0.1O3-delta　(LSCFNb)　electrode　with　40%　(ESB)　composite　electrode　was　successfully　fabricated　by　decoration　method　and　directly　assembled　on　barrier-layer-free　yttrium-stabilized　zirconia　(YSZ)　electrolyte　cells,　achieving　a　peak　power　density　of　1.32　W　cm(-2)　and　excellent　stability　at　750　degrees　C　and　250　mA　cm(-2)　for　100　h.　ESB　decoration　also　significantly　reduces　the　activation　energy　from　214　kJ　mol(-1)　for　the　O-2　reduction　on　pristine　LSCFNb　electrode　to　98　kJ　molt.　Further　microstructural　analysis　reveals　that　there　is　a　redistribution　and　migration　of　the　ESB　phase　in　the　ESB-LSCFNb　composite　toward　the　YSZ　electrolyte　under　the　influence　of　cathodic　polarization,　forming　a　thin　ESB　layer　at　the　cathode/YSZ　electrolyte　interface.　The　in　situ　formed　ESB　layer　not　only　prevents　the　direct　contact　and　subsequent　reaction　between　segregated　SrO　and　YSZ　electrolytes,　but　also　remarkably　promotes　the　oxygen　migration/diffusion　at　the　interface　for　O-2　reduction　reaction,　resulting　in　a　remarkable　increase　in　power　output　and　a　decrease　in　activation　energy.　The　present　study　clearly　demonstrated　the　in　situ　formation　of　a　highly　functional　and　active　ESB　protective　layer　at　LSCFNb　cobaltite　cathode　and　YSZ　electrolyte　interface　via　ESB-decorated　LSCFNb　composite　cathode　under　SOFC　operation　conditions.