Surface-directed modulation of MOF-templated Ni-doped CeO2 mesoporous spheres for ultrasensitive H2S detection at ppb level

The continuous release of harmful gases and increased industrial activities has made environmental monitoring essential for evaluating their impact on human health and ecosystem. In this study, a spherical nanostructure of Nickel (Ni) doped CeO 2 was derived from hydrothermally synthesized cerium-based metal-organic framework (Ce-MOF) via MOF encapsulation-calcination method for ultrasensitive detection of H 2 S at ppb level. The physical characterizations and microstructure of the Ni-CeO 2 composite revealed porous surface with a hollow spherical framework structure. The H 2 S gas-sensing performance of CeO 2 increased with Ni doping and exhibited remarkable sensitivity up to 100 ppb at low operational temperature. Notably, Ni-CeO 2 -6 composite shows an improved response of 108 (R a /R g ) at an operational temperature of 100°C. Furthermore, NC-6 displays good linearity (R 2 =0.998) towards H 2 S concentration with a low detection limit (8.68 ppb). The composite nanostructure shows good humid tolerance with minimum response deviation (6 %), on increasing the relative humidity (RH) from 15 % to 60 % at room temperature. In addition to this, the composite nanostructure shows excellent selectivity towards H 2 S, combined with good repeatability, and sustained stability. The enhanced response of Ni-doped CeO 2 can be correlated with increased surface area, porous morphology, and reactive oxygen sites on the surface. The study reveals the synergistic interplay of MOF-derived framework and Ni doping for increasing oxygen vacancies and enhancing the surface reactivity for improved gas-sensing performance.