[C12-2-C12mim][Br2]-assisted hydrothermal synthesis of hollow NiO microspheres for near-room temperature measurement of H2S

Hollow NiO microspheres were prepared using one-step hydrothermal method assisted by geminal dicationic ionic liquid (DIL) 1, 2-bis (N-dodecylimidazolyl) ethane bromide ([C₁₂-2-C₁₂mim][Br₂]). The structures of the prepared microspheres can be controlled by adjusting the concentration of ionic liquid and reaction temperature. Furthermore, the amount of ionic liquid residue in these microspheres can also be controlled by changing the calcination temperature. Among them, the NiO hollow microspheres prepared by calcining the precursor at 600 °C (Ni1–600) in air display the most excellent gas sensing performance, including high response (35.6–100 ppm H₂S) and low working temperature (50 °C). The excellent gas sensing performance of the Ni1–600 is attributed to the ionic liquid residue with appropriate content, which enhances the interaction between the analyte and the sensing material. The strong interaction effectively increases the sensitivity and reduces the working temperature of the sensor. The NiO hollow microspheres are expected to be a promising candidate material for the highly sensitive H₂S gas sensor at near room temperature.