Sm modulated oxygen and target gas adsorption for ppb-level formaldehyde detection in indoor environments

Developing highly sensitive, low detection limit, and stable formaldehyde (HCHO) sensors remains a key challenge in practical environmental health monitoring. LaFeO 3 -based sensors offer advantages such as good stability, sensitivity, and relatively low production costs. However, their response to HCHO need improvement to meet practical detection requirements. Herein, a series of Sm-doped LaFeO 3 perovskite oxides were prepared by a sol-gel method. Among these, 3 at% Sm-doped LaFeO 3 based sensor (3%Sm-LaFeO 3 ) exhibits the optimal response value (S = 115, 130 °C) to 40 ppm HCHO, along with a low detection limit (50 ppb), good selectivity, and long-term stability. Furthermore, 3%Sm-LaFeO 3 maintains reliable response (50 ppb, > 1.2) within a wide humidity range (≤ 70% RH), demonstrating its suitability for indoor HCHO detection. Density functional theory (DFT) calculations revealed two key mechanisms underlying the enhanced gas sensing performance by Sm doping. First, Sm enhances the adsorption of O 2 and promotes charge transfer, consequently increasing the amount of surface-adsorbed oxygen species. Second, Sm induces the d -band center of the local Fe 3d orbital to move upward, strengthening the bonds between the Fe 3d and the O 2p orbitals of HCHO, thereby improving HCHO adsorption. This study not only provides a highly sensitive and stable gas sensor for indoor HCHO monitoring, but also explains the dual roles of Sm species in the sensing process.