Constructing　effective　photocatalysts　with　visible　light　response　to　achieve　rapid　dehalogenation　of　polyhalogenated　compounds　remains　a　challenge　nowadays.　Herein,　Pd　nanoclusters-decorated　TiO2　nanosheets　with　surface　defects　(Pd/TNS)　are　designed　for　polyhalogenated　biphenyls　dehalogenation　under　visible　light.　Pd/TNS　is　able　to　rapidly　remove　bromine　atoms　of　4-bromobiphenyl　in　30　min.　Experimental　results　reveal　that　oxygen　vacancies　and　Ti3+　are　in-situ　generated　in　TNS　during　Pd　photodeposition,　which　extend　the　absorption　band　edge　of　Pd/TNS　to　visible　light　region.　Besides,　the　unique　two-dimensional　nanosheets　structure　of　TNS　contributes　to　a　high　surface　area　for　high　dispersion　of　Pd　nanoclusters.　Importantly,　the　Pd　nanoclusters　serve　to　activate　carbon-halogen　bond　in　polyhalogenated　biphenyls　and　hydrogen-oxygen　in　H2O.　The　high　dehalogenation　efficiency　could　be　assigned　to　a　strong　chemical　interaction　and　synergistic　effect　between　the　Pd　nanoclusters　and　TiO2(B)　nanosheets.　Finally,　a　collaborative　mechanism　is　proposed　for　photocatalytic　dehalogenation　of　polyhalogenated　biphenyls　on　Pd/TNS.　©　2020