Noble Metal-Free SnO₂/Nanoporous Zn-Based Hydroquinone Thin Film Sensor for Ultrasensitive Hydrogen Detection

Developing high-performance hydrogen sensors without noble metals remains challenging for green hydrogen energy industry applications. In this paper, a kind of simple-architecture and high-performance hydrogen sensor based on SnO₂/porous zinc hydroquinone (Zn-HQ) hybrid thin film has been developed on a Si substrate by atomic/molecular layer deposition (ALD/MLD). By introducing a 20 nm thick mesoporous Zn-HQ thin film, a 14 nm thick SnO₂/Zn-HQ sample shows excellent hydrogen-sensing performance and selectivity without noble metal modification. The response value reaches 112.54@30 ppm of H₂ at 125 °C with a response time of 26 s and a recovery time of 222.5 s, respectively. The mechanism for improved hydrogen sensitivity based on the SnO₂/porous Zn-HQ structure is proposed. On the one hand, Zn-HQ hybrid film can extract oxygen from SnO₂, while the porous structure in the film also provides channels for the diffusion of oxygen ions, thereby generating more oxygen vacancy active sites in SnO₂ films. On the other hand, the mesoporous Zn-HQ film induces the formation of numerous shallow nanopores on the SnO₂ surface by ALD conformal deposition, increasing the specific surface area for gas adsorption. Simultaneously, density functional theory (DFT) calculations confirm that H₂ has the highest adsorption energy compared with several interfering gases of CO, CH₄, NH₃, H₂S, and C₂H₅OH in the SnO₂ model containing oxygen vacancies. In summary, this work provides a new strategy for the construction of highly sensitive, selective, and reliable noble metal-free thin film hydrogen sensors at relatively low working temperature. Furthermore, the versatile ALD/MLD technology compatible with silicon technology also opens more possibilities and opportunities for the miniaturization and integration of thin film hydrogen sensors in microelectro-mechanical and artificial intelligent systems.