One-pot solvothermal synthesis of hierarchical Co-doped NiO microspheres with enhanced hydrogen sulfide sensing performances

In this study we report, for the first time, the synthesis of Co-doped NiO microspheres assembled by two-dimension nanosheets using a facile solvothermal method. The H2S gas-sensing performance of the as-prepared samples was systematically investigated. The result demonstrates that the Co–NiO sensor with Co/Ni molar ratio of 1% (1% Co–NiO) exhibits high response (12.9) and rapid response speed (110 s) to 20×10−6 H2S at 200 °C in comparison with the pure NiO sensor. Moreover, excellent selectivity, repeatability, and stability were achieved. The sensing mechanism illustrates that the superior gas-sensing properties can be attributed to two factors. (1) The hierarchical microspherical construction with an ultrahigh specific surface area of 163.1 m2 g−1 provides adequate active sites for H2S gas adsorption, porous structures, and an interlayer gap that accelerates the diffusion of H2S gas, resulting in improved sensitivity and response speed of the sensor. (2) Co-doping results in a decrease in the particle sizes (ca. 4 nm) and increase in the number of adsorbed ionized oxygen species, which improves sensitivity and selectivity. Therefore, this study provides a facile approach for the synthesis of hierarchical Co–NiO microspheres with enhanced H2S gas-sensing performance.