The　photoelectrocatalytic　(PEC)　oxidation　of　glycerol　into　highly　value-added　products　is　attractive,　but　it　is　extremely　challenging　to　limit　the　oxidation　products　to　the　valuable　C3　chemicals.　The　hole　concentration　and　surface　atomic　arrangement　of　a　photoanode　can　be　modulated　by　controlling　facet　exposure,　thus　tuning　the　activity　and　selectivity.　Herein,　we　report　for　the　first　time　the　formation　of　a　WO3　photoanode　with　predominant　exposure　of　{202}　facets　by　a　secondary　hydrothermal　method.　The　photoanode　exhibits　superior　PEC　glycerol　conversion　efficiency,　giving　an　80%　selectivity　to　glyceraldehyde　with　a　production　rate　of　462　mmol　h(-1)　m(-2).　Also,　the　faraday　efficiency　for　the　C3　product　reaches　98.6%.　We　made　comparison　between　the　{202}　facets　and　the　commonly　studied　{200}　facets　using　experimental　and　theoretical　methods.　It　is　disclosed　that　the　former　enhances　not　only　the　adsorption　and　activation　of　glycerol　via　the　terminal　hydroxyl　groups　but　also　the　desorption　of　glyceraldehyde.