Highly Sensitive and Selective Room Temperature NO₂ Gas Sensor Based on 3D BiFeO_3 − x Microflowers

High-performance chemresistive gas sensors operating at low or room temperatures are of great potential for practical applications. In this work, the oxygen vacancies-rich BiFeO_3 − x microflowers were synthesized using a facile solvothermal route. The characterized results showed that BiFeO_3 − x was assembled with nanosheets, and displayed a diameter of around 1 μm. The as-fabricated BiFeO_3 − x gas sensor exhibited fine sensing properties towards 0.5-5 ppm NO₂ under ~ 23 ^oC, including a response of 2.92 to 5 ppm NO₂, and it also maintained a response of 1.05 towards 50 ppb NO₂. The gas sensor demonstrated a theoretical limit of detection as low as 273 ppb, rapid response/recovery speed (22/69 s), good selectivity, and repeatability. The improved NO₂ sensing mechanism of enriched oxygen vacancies-BiFeO_3 − x was investigated regarding its micro-nano structure and abundant oxygen species.