Constructing surface oxygen defects at CuO-Co₃O₄ interface to boost toluene oxidation over CuO/Co₃O₄ catalysts

As a typical heterogeneous catalytic process, the catalytic combustion of toluene over Co₃O_4-based catalysts is strongly depends on the surface properties of catalysts, especially the concentration of surface oxygen defects. Here, a novel way was proposed to construct chemically bonded CuO-Co₃O₄ interface by chemical deposition of CuO onto Co₃O₄ nanoflowers. The interfacial refinement effect between CuO and Co₃O₄ support disrupted the ordered atomic arrangement and created countless unsaturated coordination sites at CuO-Co₃O₄ interface, inducing a significant generation of surface oxygen defects. Surface-rich oxygen vacancies enhanced the capacity of 20%CuO/Co₃O₄-R to adsorb and activate oxygen species. Benefiting from this, 90 % toluene conversion was reached at 228 °C over 20%CuO/Co₃O₄-R, which was much lower than that over 20%CuO/Co₃O₄-S prepared by impregnation method and CuO/Co₃O₄-mix obtained by mechanically mixing way. In-situ DRIFTS analysis revealed that toluene could be directly decomposed into benzaldehyde at the highly defective CuO-Co₃O₄ interface, leading to toluene oxidation following the path of toluene → benzaldehyde → benzoate → maleic anhydride → water and carbon dioxide over 20%CuO/Co₃O₄-R, which was significantly different from decomposition mechanism over 20%CuO/Co₃O₄-S. Additionally, 20%CuO/Co₃O₄-R displayed terrific recyclability and outstanding stability, showing good application potential.