Carbon vacancy engineering enables superior electron donation for O₂ activation over platinum/carbon nitride

Defect engineering plays a crucial role in activating molecular oxygen by modulating the local electronic and geometric structures of active sites. However, defects in metal-free materials have received comparatively little attention in this context, particularly under thermal conditions, despite reports of the favorable electron-donating properties. To systematically compare how different vacancies modulate catalytic behavior, we prepared platinum (Pt) nanoparticles supported on nearly pristine carbon nitride with minimal vacancies (CN), carbon nitride with carbon vacancies (Cv-CN), and carbon nitride with nitrogen vacancies (Nv-CN). Combined experimental and theoretical analyses reveal that carbon vacancies induce stronger electron localization than nitrogen vacancies, resulting in a significant increase in electron density at Pt sites. The synergistic interaction between Pt atoms and adjacent nitrogen atoms surrounding carbon vacancies facilitates electron donation to the π* antibonding orbitals of adsorbed O₂, thereby enhancing O₂ activation. Consequently, Pt supported on Cv-CN (Pt/Cv-CN) achieves a light-off temperature (T₅₀, the temperature for 50% toluene conversion) of 185 °C with only 0.1 wt% Pt, substantially lower than those of Pt supported on Nv-CN (Pt/Nv-CN, 202 °C) and Pt supported on CN (Pt/CN, 210 °C). This work elucidates the critical role of carbon vacancies in optimizing the electronic environment of carbon nitride and enhancing oxygen activation at the Pt-support interface, thereby providing a systematic strategy for designing high performance catalysts with minimal noble metal loading.