| Summary: | A high-performance zinc oxide/tin dioxide (ZnO/SnO<sub>2</sub>) humidity sensor was developed using a simple solvothermal method. The sensing mechanism of the ZnO/SnO<sub>2</sub> humidity sensor was evaluated by analyzing its complex impedance spectra. The experimental results prove that the ZnO/SnO<sub>2</sub> composite material has a larger specific surface area than pure SnO<sub>2</sub>, which allows the composite material surface to adsorb more water to enhance the response of the ZnO/SnO<sub>2</sub> humidity sensor. ZnO can also contribute to the generation of oxygen-rich vacancies on the ZnO/SnO<sub>2</sub> composite material surface, allowing it to adsorb a large amount of water and rapidly decompose water molecules into conductive ions to increase the response and recovery speed of the ZnO/SnO<sub>2</sub> humidity sensor. These characteristics allowed the Z/S-2 humidity sensor to achieve a higher response (1,225,361%), better linearity, smaller hysteresis (6.6%), faster response and recovery speeds (35 and 8 s, respectively), and long-term stability at 11–95% relative humidity. The successful preparation of the ZnO/SnO<sub>2</sub> composite material also provides a new direction for the design of SnO<sub>2</sub>-based resistance sensors with high humidity-sensing performance.
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