Surface　decoration　of　photoanodes　with　oxygen　evolution　cocatalysts　is　an　efficient　approach　to　improve　the　photoelectrochemical　water　splitting　performance.　Herein,　ultrafine　CoOx　was　selectively　immobilized　on　the　surface　of　BiVO4/WO3　photoanode　by　using　the　photogenerated　holes　to　in-situ　oxidize　Co4O4　cubane.　The　composited　photoanode　(CoOx/BiVO4/WO3)　displayed　an　enhanced　photoelectrochemical　(PEC)　water　oxidation　performance,　with　a　photocurrent　density　of　2.3　mA/cm(2)　at　1.23　V-RHE　under　the　simulated　sunlight　irradiation,　which　was　2　times　higher　than　that　of　bare　BiVO4/WO3.　The　characterization　results　for　the　morphological,　optical　and　electrochemical　properties　of　the　photoelectrodes　revealed　that,　the　enhanced　PEC　performances　could　be　attributed　to　the　improved　charge　carrier　separation/transport　behaviors　and　the　promoted　water　oxidation　kinetics　when　the　photoelectrodes　were　loaded　with　CoOx.　(C)　2019　Hydrogen　Energy　Publications　LLC.　Published　by　Elsevier　Ltd.　All　rights　reserved.