A-site　deficient　(La0.6Sr1.4)0.95Mn1-xBxO4　(x　=　0,　0.1,　B=　Co,　Ni,　Cu)　(LSMBO4)　Ruddlesden–Popper　oxides　were　demonstrated　as　promising　symmetrical　electrodes　for　Sc2O3　stabilized　ZrO2　(SSZ)　electrolyte　supported　solid　oxide　fuel　cells　(SOFCs).　The　formation　of　oxygen　vacancies　is　facilitated　with　the　B-site　transition　metal　doping.　A-site　defect　promotes　the　exsolution　of　catalytic　Co,　Ni　or　Cu　nanoparticles　on　the　surface　of　materials　in　reducing　atmosphere.　The　electrochemical　performances　in　air　and　reducing　atmosphere　are　significantly　optimized　via　the　substitution　of　Mn　by　Co,　Ni　or　Cu　and　exsolved　metallic　nanoparticle　catalysts.　Especially,　the　materials　doped　by　B-site　with　Cu　shows　the　highest　electrical　conductivity　of　37.54　S　cm−1　and　6.82　S　cm−1　and　lowest　polarization　resistance　of　0.12　Ω　cm2　and　0.32　Ω　cm2　at　750　°C　in　air　and　5%　H2/N2,　respectively.　The　maximum　power　density　of　623.1　mW　cm−2　at　750　°C　is　achieved　for　an　electrolyte-supported　symmetrical　single　cell　with　the　LSMBO4-SSZ　composite　electrode　operating　with　pure　H2.　All　these　results　indicate　that　LSMBO4　can　be　promising　candidates　for　symmetric　electrodes　of　SOFCs.　©　2020　Elsevier　Ltd