Pr-Doped Three-Dimensionally Ordered Macroporous In₂O₃ for Highly Sensitive and Highly Selective Detection of Formaldehyde

Formaldehyde is a typical indoor toxic gas that can infect the human respiratory tract in excessive inhalation and even has the risk of causing cancer. In this work, Praseodymium (Pr)-doped 3-D ordered macroporous (3DOM) In2O3 nanomaterials were prepared by a one-step colloidal crystal template method. The In2O3/3% Pr-based sensor showed a high response value (~428), high sensitivity (3.37 ppm
$^{-{1}}$
), low detection limit (1.97 ppb), and high selectivity for 100 ppm formaldehyde gas at 240 °C with fast response/recovery in a short period of time (15 s/118 s). X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results show that Pr is successfully doped into the In2O3 lattice and inhibits In2O3 grain growth, causing lattice distortion and increasing the sensing material’s oxygen vacancy defects and adsorbed oxygen content. UV–Vis diffuse reflectance spectroscopy and Hall test results show that Pr doping narrows the bandgap energy and improves the Hall electron mobility of the sensing material. High adsorbed oxygen content and Hall electron mobility of In2O3/3% Pr contributed to the high-formaldehyde sensing performance.