Oxygen defect engineering modifies NiFe₂O₄ for efficient detection of n-butanol gas

Prussian blue analogs (PBA) were etched with a weak base and subsequently sulfurized to regulate the oxygen vacancy content, leading to the preparation of defect-rich spinel bimetallic oxide NiFe₂O₄. This approach successfully constructed a gas sensor with high response and excellent stability, and the material was systematically characterized. The results show that weak base etching regulates the morphology of PBA, and sulfur doping is employed to control the oxygen vacancy content. Gas sensing results confirmed that the modified NiFe₂O₄-NCs@S exhibited superior n-butanol gas sensing performance. Specifically, the sensing response of NiFe₂O₄-NCs@S to 100 ppm n-butanol at 275 °C reached 59.29, representing a 9.9-fold enhancement compared with NiFe₂O₄-PBA (response = 5.98). In addition, comprehensive tests demonstrate that the sensor possesses reliable selectivity, long-term stability and repeatability. To investigate the sensing mechanism, UV-vis spectroscopy and electrochemical characterizations were performed to verify that oxygen vacancies boost gas-sensing properties via band gap narrowing and electronic structure modulation. This work offers a novel strategy for developing high-response n-butanol gas sensors.