Precisely　constructed　dispersion　of　well-defined　single-atom　active　centers　on　the　semiconductor　could　allow　of　the　investigation　of　reaction　mechanisms,　yet　targeted　delivery　of　solar　energy　to　steer　the　charge　kinetics　for　hydrogen　evolution　remains　challenging.　Here　we　realize　the　location　of　isolated　Co　atoms　on　the　TiO2　nanosheets　with　the　thickness　of　6　nm,　providing　highly　active　catalytic　sites　for　the　significantly　boosted　photocatalytic　hydrogen　evolution.　X-ray　absorption　fine　structure　measurements　verify　that　the　atomically　dispersed　Co　is　successfully　grafted　on　the　surface　of　TiO2　nanosheets.　Experimental　exploration　and　theoretical　demonstration　not　only　confirm　the　isolated　Co　atoms　perform　as　reactive　sites,　but　also　verify　that　the　electron　transfer　and　hydrogen　adsorption/desorption　processes　can　be　greatly　accelerated　via　the　effective　Co-O　electronic　coupling　in　atomic　scale,　thereby　facilitating　the　hydrogen　evolution.