Facile Greener Synthesis of CoTiO₃/TiO₂ Composite Nanocatalysts: Understanding the Origin of Synergistic Effect

Understanding the composition-activity relationship is essential for exploiting the synergistic properties of composite nanomaterials in catalytic processes. This article provides insights into the origin of the synergistic effect in composite nanocatalysts by constructing different compositions of well-defined CoTiO₃/TiO₂ nanoparticles (NPs) with various Ti : Co weight ratios of 2 : 1 (C₁) and 1 : 1 (C₂). An environmentally benign method utilizing aqueous cinnamon extract was employed for the catalyst preparations. Catalytic tests for the reductive degradation of Congo Red and rhodamine B dyes reveal an activity order of C₁ > C₂ > TiO₂ NPs, suggesting possible surface reconstruction in the composite nanocatalytic system. Detailed structural and compositional analyses indicate that the exceptional catalytic performance of C₁ NPs is closely related to synergistic electronic and strain effects. This synergistic effect in composite NPs can be optimized by adjusting the ratio of constituents, which is anticipated to play a more crucial role in catalysis than particle size. Furthermore, the composite C₁ NPs exhibit remarkable robustness, maintaining recyclability up to the fifth cycle with only an 8.51% loss in performance.