Large　quantities　of　marine　algae　are　annually　produced,　and　have　been　disposed　or　burned　as　solid　waste.　In　this　work,　porous　carbons　were　prepared　from　three　kinds　of　marine　algae　(Enteromorpha,　Laminaria,　and　Chlorella)　by　a　two-step　activation　process.　The　as-prepared　carbon　materials　were　doped　with　cobalt　(Co)　and　applied　as　catalysts　for　oxygen　reduction　reaction　(ORR).　Our　results　demonstrated　that　Co-doped　porous　carbon　prepared　from　Enteromorpha　sp.　(denoted　by　Co-PKEC)　displayed　excellent　catalytic　performance　for　ORR.　Co-PKEC　obtained　a　half-wave　potential　of　0.810　V　(vs.　RHE)　and　a　maximum　current　density　of　4.41　mA/cm2,　which　was　comparable　to　the　commercial　10%　Pt/C　catalyst　(E1/2　=　0.815　V,　Jd　=　4.40　mA/cm2).　In　addition,　Co-PKEC　had　excellent　long-term　stability　and　methanol　resistance.　The　catalytic　ability　of　Co-PKEC　was　evaluated　in　a　one-chamber　glucose　fuel　cell.　The　maximum　power　density　of　the　fuel　cell　equipped　with　the　Co-PKEC　cathode　was　33.53　W/m2　under　ambient　conditions,　which　was　higher　than　that　of　the　fuel　cell　with　a　10%　Pt/C　cathode.　This　study　not　only　demonstrated　an　easy-to-implement　approach　to　prepare　robust　electrochemical　catalyst　from　marine　algal　biomass,　but　also　provided　an　innovative　strategy　for　simultaneous　waste　remediation　and　value-added　material　production.　©　2019　by　the　authors.　Licensee　MDPI,　Basel,　Switzerland.