This work for the first time reports the promoting effect of strong electronic metal-support interaction (EMSI) in Pt/TiO₂-V_O (V_O: oxygen vacancy) for gas-phase CO₂ photoreduction. A novel in-situ surface hydrogenation was developed to prepare hydrogenated Pt/TiO₂-V_O in a continuous, high throughput diffusion flame aerosol reactor. The combined results of various characterization techniques confirmed the presence of EMSI between Pt and defective TiO₂-V_O resulted in the enhanced electronic density of Pt nanoparticles. Both the modulated electronic structure of Pt and surface oxygen vacancies simultaneously promoted the activation of surface adsorbed carbon intermediates and facilitated the separation of photogenerated charges, eventually boosting the photocatalytic activity of Pt/TiO₂-V_O. The optimized Pt/TiO₂-V_O demonstrated a high quantum yield of 1.49% with high CH₄ selectivity (81%), which rendered 5.8- and 1.2-fold enhancements over its counterparts of TiO₂-V_O and Pt/TiO₂. More significantly, the EMSI also played a critical role in preserving the surface metallic Pt⁰ and oxygen vacancies, and in sustaining high activity of the Pt/TiO₂-V_O, whereas rapid catalytic deactivation are observed for both TiO₂-V_O and Pt/TiO₂.