Oxygen Vacancies Modulation in CoFe2O4 via Two‐Step Incorporation of Synergistic TiO2/MXene and Carbon for Enhanced Acetone Sensing

Abstract Oxygen vacancy concentration in metal oxides is crucial to gas sensing performance. This study introduces a novel strategy of oxygen vacancies modulation on CoFe 2 O 4 , by two‐step controllable incorporation of TiO 2 @MXene and carbon. In the first step, MXene simultaneously acts as an incorporation agent and a titanium source to grow TiO 2 and regulate the oxygen vacancy concentration in CoFe 2 O 4 . The fabricated n‐n heterojunctions of TiO 2 /CoFe 2 O 4 further induced a gradient distribution of oxygen vacancies through energy band bending. And a second step, combining glucose as a carbon source, further increases the oxygen vacancy concentration in CoFe 2 O 4 by chemical reduction during a hydrothermal process, leading to the formation of a CoFe 2 O 4 ‐TiO 2 @MXene‐C nanostructured composite. Through controlling the glucose content, the ratio of Co 3+ to Co 2+ within the composite can be sequentially adjusted, which allows for the further regulation of oxygen vacancy concentration on the composite surface. The effectiveness of this two‐step incorporation is demonstrated through enhanced acetone sensing performance, providing valuable insights into the fabrication of high‐performance metal oxide‐based gas sensors via controlled oxygen vacancy modulation.