Low-temperature H2S sensor based on in situ growth of hierarchical CuO/NiO microspheres and the sensing mechanism

In situ growth of nanomaterials combined with well-defined hierarchical structure may endow a gas sensor with superior sensing capability. Herein, the hierarchical CuO/NiO microspheres were in situ grown on ceramic tubes via a facile one-step ionic liquid (IL)-assisted solvothermal process with subsequent calcination. The resultant CuO/NiO composites demonstrated the interlaced nanosheets-supported microspheres, polycrystalline nature and mesoporous structure. Compared with pristine NiO deposited film sensors, the 4.49 at% CuO modified NiO microspheres sensors exhibited enhanced H₂S sensing performances at 92 °C. The response (1157.4) to 100 ppm H₂S gas was 7.5 times as high as that of pristine NiO (154.2), and the detection limit was further decreased from 0.1 ppb of the pristine NiO sensor to 0.05 ppb. The dominant H₂S sensing mechanism was elaborated from the view of p-p heterojunction, hierarchical architecture as well as the synergistic effect of CuO decorated NiO microspheres. Thus, the in situ deposited sensors based on hierarchical CuO/NiO microspheres presented high selectivity, rapid response and recovery speed, and good stability towards ppm and ppb levels of H₂S gas, making it suitable for real-time monitoring of H₂S gas in complex environments.