Exposure Surface Active Sites of Perovskite‐Type LaFeO₃ Gas Sensors by Selectively Dissolving La Cations for Enhancing Gas Sensing Properties to Acetone

Abstract While perovskite metal oxide semiconductors (MOS) gas sensors have great potential for detecting various hazardous gases, the surface enrichment of inactive A‐sites severely limits their ability to obtain excellent gas sensing properties. Herein, one simple and facile citric acid etching method is reported with the aim of significantly improving the acetone sensing properties of perovskite LaFeO₃ (LFO) by surface structure optimization. Structural characterization shows that citric acid selectively solubilized the A‐site cations and inhibits the occurrence of La segregation on the surface without destroying the perovskite structure, thus increasing the exposure of the active site Fe. At the operating temperature of 200 °C, the response of etched LFO for 20 ppm acetone reaches 50, which is almost 12 times higher than that of pristine LFO sample. Meanwhile, the etched LFO samples also exhibit low detection limits (50 ppb), good selectivity, and stability. The enhanced gas sensitivity is attributed to near‐perfect surface metal ion ratio (La/Fe atomic ratio = 0.97) and abundant oxygen species concentration. This work provides an avenue to enhance the acetone sensing properties and beyond by intentional structural modification, which not only has great scientific meaning, but also valuable potential for industrial and domestic applications.