Oxygen vacancy defects engineering on Ce-doped α-Fe2O3 gas sensor for reducing gases

Surface oxygen vacancy defects (OV) are regarded to be beneficial to the gas sensing behavior by significantly improving the carrier density and providing more oxygen adsorption sites. In this work, Ce-doped α-Fe2O3 composites with abundant OV defects were synthesized using an oil bath method assisted with annealing treatment. Morphological characterization results indicate that the lamellar architecture of α-Fe2O3 is transformed to nanospheres composed of massive nanoparticles with small sizes (7–9 nm) after introducing Ce elements. Gas sensing results show that the FeCe10 (Fe/Ce = 10:1) sensors exhibit enhanced acetone sensing response of 26.3–100 ppm gas at the operating temperature of 220 °C toward that of pure α-Fe2O3. Most importantly, X-ray photoelectron spectroscopy and electron spin resonance spectroscopy results confirm that the sensing responses of Ce-doped α-Fe2O3 sensors are directly related to the OV defects, that is, the larger the quantity of the OV defects, the higher the sensing response. The unpaired electrons trapped in OV defects can provide more active sites for adsorption of oxygen and acetone molecules, resulting in a thicker depletion layer and a higher potential barrier. Our work highlights the decisive role of OV defects in gas sensors, which can also provide a rational approach to boost the sensing performance.