Mechanistic Investigation of the Enhanced Formaldehyde-Sensing Performance of Fe-Containing Metal Oxides

Formaldehyde has been identified as one of the most harmful indoor air pollutants. Metal oxide semiconductor-based formaldehyde sensors have attracted widespread attention due to their excellent physicochemical properties. According to previous studies, iron-containing metal oxides exhibit outstanding formaldehyde sensing performance. To verify the importance of the Fe element and elucidate the underlying reasons, we synthesized a series of metal oxides, including different ternary perovskite materials, Fe₂O₃, and various spinel metal oxides. Material characterization results confirmed that the prepared materials possessed comparable surface morphologies and crystallographic properties. However, sensing tests demonstrated the superior formaldehyde sensing performance of iron-containing compounds. The special conduction-type switch feature for Fe₂O₃ was also demonstrated. By combining in-operando DRIFT measurements, the sensing mechanism was elucidated, and different pathways for formaldehyde oxidation on the surfaces of perovskite, Fe₂O₃, and spinel oxides were identified.