Ni-Doped SnO Microplates for Carbon Monoxide Gas Detection

Undoped and Ni-doped SnO were synthesized using a microwave-assisted hydrothermal method to analyze the influence of Ni-doped SnO nanostructures on CO detection. The scanning electron microscopy (SEM) analysis revealed a predominantly tetragonal SnO phase, with a minor proportion of the tetragonal SnO₂ phase. X-ray photoelectron spectroscopy (XPS) confirmed the SnO phase without the NiO_x phase on the microplate surfaces. The images showed micrometric plates with SnO (001) surfaces. The presence of Ni led to an increase in the carrier concentrations, resulting in enhanced conductivity. Additionally, density functional theory (DFT) calculations indicated that Ni doping in the outermost layer significantly enhanced CO affinity via carbon coordination, while oxygen-bound configurations became unstable. Electrical measurements showed a slight decrease in the activation energy (E_a) for the Ni-doped sample under a reductive atmosphere. This behavior facilitates the use of this material at room temperatures, which is technologically desirable for CO sensor devices.