Intrinsic characteristic and mechanism in enhancing H₂S sensing of Cd-doped α-MoO₃ nanobelts

Pure and Cd-doped orthorhombic molybdenum trioxide (α-MoO ₃) nanobelts with width of 200-800 nm and length of several micrometers have been successfully synthesized by a facile and low temperature (120 °C) hydrothermal method without any surfactant or template. The crystal structure and morphology of the products were characterized by XRD and FESEM. The sensing measurements reveal that the synthesized samples not only exhibit high response to H₂S but also small cross-sensing to other reducing gases. The change of intrinsic defects in Cd-doped sample is responsible for the enhancement of the sensing properties, which has been confirmed by the room temperature PL, Raman and XPS. The response transients of the sensors under different gas concentrations were measured and modeled using L-H heterogeneous reaction mechanism. Origin and mechanism of the enhanced gas sensing for 5 wt% Cd-doped sample were analyzed in detail according to the characteristic of PL and XPS.