Enhancing Oxygen Activation Ability by Composite Interface Construction over a 2D Co3O4-Based Monolithic Catalyst for Toluene Oxidation

Developing robust metal-based monolithic catalysts with efficient oxygen activation capacity is crucial for thermal catalytic treatment of volatile organic compound (VOC) pollution. Two-dimensional (2D) metal oxides are alternative thermal catalysts, but their traditional loading strategies on carriers still face challenges in practical applications. Herein, we propose a novel in situ molten salt-loading strategy that synchronously enables the construction of 2D Co₃O₄ and its growth on Fe foam for the first time to yield a unique monolithic catalyst named Co₃O₄/Fe-S. Compared to the Co₃O₄ nanocube-loaded Fe foam, Co₃O₄/Fe-S exhibits a significantly improved catalytic performance with a temperature reduction of 44 °C at 90% toluene conversion. Aberration-corrected scanning transmission electron microscopy and theoretical calculation suggest that Co₃O₄/Fe-S possesses abundant 2D Co₃O₄/Fe₃O₄ composite interfaces, which promote the construction of active sites (oxygen vacancy and Co³⁺) to boost oxygen activation and toluene chemisorption, thereby accelerating the transformation of reaction intermediates through Langmuir-Hinshelwood (L-H) and Mars-van Krevelen (MvK) mechanisms. Moreover, the growth mechanism reveals that 2D Co₃O₄/Fe₃O₄ composite interfaces are generated in situ in molten salt, inducing the growth of 2D Co₃O₄ onto the surface lattice of 2D Fe₃O₄. This study provides new insights into enhancing oxygen activation and opens an unprecedented avenue in preparing efficient monolithic catalysts for VOC oxidation.