Controlled oxygen vacancies of ZnFe2O4 with superior gas sensing properties prepared via a facile one-step self-catalyzed treatment

It is widely accepted that oxygen vacancies play an important role in high-performance gas sensors. Unfortunately, the mechanisms responsible for improved gas sensing performance due to oxygen vacancies are not yet well understood because the formation of oxygen vacancy-rich sensors is always accompanied by other variations, especially changes in chemical composition, particle size, and surface morphology. In this work, ZnFe2O4 with controllable oxygen vacancies was prepared by a facile one-step self-catalyzed treatment, shake and heat, in which commercial ZnFe2O4 served as the raw material and catalyst for tartaric acid oxidation. Compared to commercial ZnFe2O4, the as-prepared ZnFe2O4 had a similar crystal structure, particle size and morphology but possessed controllable oxygen vacancies, which was validated by XRD, SEM and XPS. The asprepared oxygen vacancy-rich ZnFe2O4 showed superior performance in sensing acetone compared to the raw materials, i.e., commercial ZnFe2O4. It is proposed that the sensing properties improved because the oxygen vacancies narrowed the band gap and adsorbed more oxygen. This work proves that oxygen vacancies can indeed improve the sensing properties alone and demonstrate a new facile synthesis strategy for oxygen vacancyrich sensors.