Bimetallic-based spinels are potential materials for toluene oxidation ascribing to their remarkable stability and oxidation activity. However, the insufficient toluene adsorption capacity and limited reactive oxygen species severely restrict their low-temperature catalytic reactivity. This study reports a facile two-step solvothermal strategy for the synthesis of core–shell structured CrO_x/NiCo_xO₄ catalyst, which exhibits excellent toluene oxidation performance with T₅₀ and T₉₀ values of 187 and 218 °C, respectively, and the toluene conversion remains above 90 % at 218 °C for 20 h. The in-situ DRIFTs indicate that the oxidation of toluene to CO₂ and H₂O follows Mars-van Krevelen (MvK) mechanism, and the rate limiting step is the oxidation of quinone to maleic anhydride. The strong interaction between core NiCo_xO₄ and shell CrO_x regulates the morphology of CrO_x from particles to porous flocculent structure, which increases the porosity of catalyst and promotes the adsorption of toluene for further oxidation. Moreover, the interaction promotes the charge transfer from NiCo_xO₄ to CrO_x, which increases the adsorbed oxygen species contents and the redox capability of the catalyst. A further density functional theory (DFT) calculation confirms that the core NiCo_xO₄ is the main active component, where the oxygen vacancy formation energy of NiCo_xO₄ and CrO_x decrease from 2.43 and 3.85 eV to 0.31 and 1.52 eV, while the toluene adsorption energy decrease from −0.04 and −0.94 eV to −5.29, and −4.48 eV, respectively, which evidently demonstrates that the formation of core–shell structured CrO_x/NiCo_xO₄ would significantly promote the adsorption and oxidation of toluene, thereby exhibiting excellent low temperature toluene oxidation reactivity.

双金属尖晶石因其卓越的稳定性和氧化活性而成为甲苯氧化的潜在材料。然而，甲苯吸附能力不足和活性氧物种有限严重限制了其低温催化反应活性。本研究报告了一种简便的两步溶剂热策略，用于合成核壳结构的 CrO _x /NiCo _x O ₄催化剂，该催化剂表现出优异的甲苯氧化性能，T ₅₀和 T ₉₀值分别为 187 和 218 °C，并且在 218 °C 下 20 小时，甲苯转化率保持在 90% 以上。原位DRIFT表明，甲苯氧化成CO ₂和H ₂ O遵循Mars-van Krevelen (MvK)机理，限速步骤是醌氧化成马来酸酐。核NiCo _x O ₄与壳CrO _x之间的强相互作用调节CrO _x的形貌从颗粒到多孔絮状结构，增加了催化剂的孔隙率，促进甲苯的吸附进一步氧化。此外，这种相互作用促进了电荷从NiCo _x O ₄到CrO _x的转移，从而增加了吸附氧含量和催化剂的氧化还原能力。进一步的密度泛函理论（DFT）计算证实核心NiCo _x O ₄是主要活性成分，其中NiCo _x O ₄和CrO _x的氧空位形成能从2.43和3.85 eV下降到0.31和1.52 eV，而甲苯吸附能分别从-0.04和-0.94 eV下降到-5.29和-4.48 eV，这明显表明核壳结构CrO _x /NiCo _x O ₄的形成会显着促进甲苯的吸附和氧化，从而表现出优异的低温甲苯氧化反应活性。