Recently,　single-atom　catalysts　have　aroused　extensive　attention　in　fields　of　clean　energy　and　environmental　protection　due　to　their　unique　activity　and　efficient　utilization　of　the　active　atoms.　It　is　of　great　importance　but　still　remains　a　great　challenge　to　unveil　the　effect　of　single　atoms　on　precise　catalysis.　Herein,　it　is　reported　that　doping　TiO2　hollow　microspheres　(TiO2-HMSs)　with　single　atomic　Fe　can　boost　the　photoreactivity　of　TiO2-HMSs　towards　NO　oxidation　due　to　the　synergistic　effects　of　atomically　dispersed　Fe　and　bonded　Ti　atom　which　act　as　dual　active　sites.　The　atomically　dispersed　Fe　atoms　occupy　the　subsurface　Ti　vacancies,　and　the　interaction　between　Ti　3d　and　Fe　3d　orbitals　result　in　the　formation　of　Fe-Ti　bond.　Single　atomic　Fe　modulates　the　electronic　structure　of　the　bonded　Ti　atoms　by　electron　transfer,　which　facilitates　the　adsorption　and　activation　of　NO　and　O-2　at　Fe　and　bonded　Ti　sites,　respectively.　In　addition,　the　introduction　of　single　atomic　Fe　sharply　suppresses　the　production　of　toxic　NO2　byproduct.　The　synergistic　effects　of　the　dual　active　sites　then　cause　a　drastic　promotion　in　photocatalytic　oxidation　of　NO.