Oxygen　evolution　reaction　(OER)　by　photocatalysis　remains　as　a　bottleneck　for　overall　water　splitting.　Herein,　we　report　a　new　use　of　conventional　Co　doped　ZnO　nanorods　with　a　band　gap　of　1.77　eV　as　a　noble-metal-free　photocatalyst　for　OER　under　visible　light　illumination.　A　remarkable　performance　of　ca.　191.8　mu　mol/h　is　realized　by　50　mg　of　the　optimal　Co　doped　ZnO　photocatalyst　and　visible　light　illumination　(＞420　nm).　The　apparent　quantum　yields　are　ca.　22.8　%　and　43.5　%　at　the　wavelength　of　420　nm　and　380　nm,　respectively.　This　research　suggests　the　potential　of　this　conventional　material　to　hardness　sunlight　for　efficient　water　splitting　and　other　advanced　photocatalytic　applications.