Non-Precious Metal Catalysts with Gradient Oxidative Dual Sites Boost Bimolecular Activation for Catalytic Oxidation Reactions

Catalytic oxidation emerges as a highly promising and cost-effective approach for eliminating gaseous pollutants, greenhouse gases, and volatile organic compounds (VOCs) from industrial exhaust streams. However, achieving the simultaneous activation of O₂ and substrate molecules at low temperatures using non-precious metal catalysts remains a significant challenge. In this study, we introduce gradient oxidative Cu─O─Ti/Cu─O─Cu dual sites that enhance bimolecular activation for catalytic oxidation reactions. The catalyst, Ti-doped CuO, is synthesized on a TiO₂ support through the immobilization of Cu^2⁺ on NO₃⁻-grafted TiO₂, followed by thermal treatment. The resulting gradient oxidative Cu─O─Ti/Cu─O─Cu sites exhibit exceptional catalytic oxidation activity for NH₃ and various VOCs at low temperatures, matching the performance of precious metal-based catalysts. Notably, during NH₃ oxidation, Cu─O─Ti sites enhance the activation of both O₂ and NH₃. HNO intermediates formed on Cu─O─Ti sites react with NH intermediates on neighboring Cu─O─Cu sites—producing N₂ and H₂O via an imide mechanism—which effectively lowers the reaction barrier for catalytic NH₃ oxidation. As such, dual sites in non-precious metal catalysts show promising results for advancing future catalytic oxidation technologies.