For　wide　application　of　metal-air　batteries,　the　key　factor　is　the　development　of　catalysts　for　air　cathodes.　In　the　present　study,　PdCo/C　bimetallic　nanocatalysts　are　prepared　by　a　facile　borohydride　reduction　method.　To　improve　the　activity　and　stability,　the　catalysts　are　heat-treated　at　200　degrees　C　in　H-2/Ar　atmosphere　from　4　h　to　24　h.　The　optimal　heat　treatment　time　is　found　to　be　8　h,　at　which　the　highest　activity　for　both　oxygen　reduction　reaction　and　oxygen　evolution　reaction　is　obtained.　With　the　8　h　heat-treated　PdCo/C　catalyst,　the　rechargeable　zinc-air　battery　exhibits　a　high　power　density　of　180　mW　cm(-2)　and　retains　stability　for　more　than　50　h　at　a　discharge-charge　current　density　of　10　mA　cm(-2),　while　the　magnesium-air　battery　obtains　a　power　density　of　more　than　200　mW　cm(-2)　and　remains　stable　within　8　h　at　a　discharge　current　density　of　65　mA　cm(-2).　(C)　2018　Hydrogen　Energy　Publications　LLC.　Published　by　Elsevier　Ltd.　All　rights　reserved.