Single-atom　catalysis　has　become　the　most　active　new　frontier　in　energy　conversion　applications　due　to　its　remarkable　catalytic　activity　and　low　material　consumption.　However,　the　issue　of　atom　aggregation　during　the　synthesis　process　or　catalytic　reaction　must　be　overcome.　In　this　work,　we　have　developed　a　one-step　photo-deposition　process　to　fabricate　Pt　single-atom　catalysts　(SACs)　on　nitrogen　doped　carbon　dots　(NCDs).　The　Pt-NCDs　were　then　hybridized　with　TiO2　to　achieve　high　hydrogen　generation　activity　and　to　understand　the　fundamentals　at　the　Pt/NCD/TiO2　interface.　The　synergistic　effect　of　Pt　SAC　and　NCDs　with　maximized　atomic　efficiency　of　Pt　and　improved　charge　transfer　capability　provides　a　new　strategy　to　rationally　design　a　multi-scale　photocatalyst　structure　to　achieve　high　H2　evolution　efficiency.　The　facile　synthesis　process　also　holds　great　potential　for　various　applications　such　as　electrocatalysis,　heterogeneous　catalysis　and　drug　delivery,　providing　a　promising　way　to　reduce　the　high　cost　of　noble　metals.　©　2020　The　Royal　Society　of　Chemistry.