Enhancing Oxygen Activation Ability by Composite Interface Construction over a 2D CoO-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 CoO and its growth on Fe foam for the first time to yield a unique monolithic catalyst named CoO/Fe-S. Compared to the CoO nanocube-loaded Fe foam, CoO/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 CoO/Fe-S possesses abundant 2D CoO/FeO composite interfaces, which promote the construction of active sites (oxygen vacancy and Co) 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 CoO/FeO composite interfaces are generated in situ in molten salt, inducing the growth of 2D CoO onto the surface lattice of 2D FeO. This study provides new insights into enhancing oxygen activation and opens an unprecedented avenue in preparing efficient monolithic catalysts for VOC oxidation.