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 CoFe2O4, by two-step controllable incorporation of TiO2@MXene and carbon. In the first step, MXene simultaneously acts as an incorporation agent and a titanium source to grow TiO2 and regulate the oxygen vacancy concentration in CoFe2O4. The fabricated n-n heterojunctions of TiO2/CoFe2O4 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 CoFe2O4 by chemical reduction during a hydrothermal process, leading to the formation of a CoFe2O4-TiO2@MXene-C nanostructured composite. Through controlling the glucose content, the ratio of Co3+ to Co2+ 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.