It　is　desirable　but　challenging　for　ruthenium　(Ru)-based　chalcogenides　to　achieve　high　activity　and　good　durability　toward　oxygen　reduction　reaction　(ORR)　in　fuel　cell　applications.　In　this　work,　a　facile　microwave　route　followed　by　heat　treatment　was　utilized　to　synthesize　carbon　supported　ruthenium　tellurium　(RuTe2/C)　catalysts,　and　the　effects　of　heat　treatment　temperature　on　crystal　structure,　microstructure,　chemical　state,　electrocatalytic　activity,　and　fuel　cell　performance　were　studied.　The　mixed　phase　of　predominant　orthorhombic　RuTe2　and　minor　hexagonal　Ru　was　identified　as　dual　active　sites　for　RuTe2/C　catalysts.　Density　functional　theory　calculations　demonstrated　that　orthorhombic　RuTe2　exhibits　enhanced　intrinsic　activity　relative　to　pure　Ru　due　to　the　weakened　absorption　energies　of　oxygen　intermediates.　Because　of　the　smallest　nanoparticle　size　and　complete　formation　of　an　orthorhombic　RuTe2　structure,　the　best　ORR　performance　was　achieved　with　the　RuTe2/C　catalyst　heat　treated　at　400　°C,　showing　a　maximum　half-wave　potential　of　0.70　V　and　only　a　70　mV　drop　(10.0%　loss)　after　6000　potential　cycles.　In　a　H2/O2　fuel　cell　test,　the　best-performed　RuTe2/C　catalyst　delivered　a　maximum　power　density　of　672　mW⋅cm−2　using　a　low　cathode　Ru　loading　of　0.18　mg·cm−2,　which　is　the　best　performance　ever　achieved　for　the　Ru-based　catalysts.　After　6000　cycles　of　rigorous　accelerated　degradation　test,　the　cell　performance　decayed　by　55.4%　because　of　the　migrations　of　Te　and　Ru　from　the　cathode　side　to　the　anode　side　and　the　growth　of　the　RuTe2/C　nanoparticles.　©　2022