Noble Metal-Free SnO 2 /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 SnO 2 /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 SnO 2 /Zn-HQ sample shows excellent hydrogen-sensing performance and selectivity without noble metal modification. The response value reaches 112.54@30 ppm of H 2 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 SnO 2 /porous Zn-HQ structure is proposed. On the one hand, Zn-HQ hybrid film can extract oxygen from SnO 2, while the porous structure in the film also provides channels for the diffusion of oxygen ions, thereby generating more oxygen vacancy active sites in SnO 2 films. On the other hand, the mesoporous Zn-HQ film induces the formation of numerous shallow nanopores on the SnO 2 surface by ALD conformal deposition, increasing the specific surface area for gas adsorption. Simultaneously, density functional theory (DFT) calculations confirm that H 2 has the highest adsorption energy compared with several interfering gases of CO, CH 4, NH 3, H 2 S, and C 2 H 5 OH in the SnO 2 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.