Pd nanoparticles decorated SnO2 ultrathin nanosheets for highly sensitive H2 sensor: Experimental and theoretical studies

This study is attempted to improve the hydrogen sensing performance of SnO2 based sensors by simultaneously employing two strategies of morphology control and noble metal loading. Therefore, SnO2 ultrathin nanosheets with thickness not exceeding 3.5 nm were successfully synthesized by a hydrothermal method and then different content of Pd nanoparticles were uniformly loaded onto SnO2 surface by in situ reduction with ascorbic acid. The gas sensing properties demonstrated that the introduction of Pd not only altered the selectivity of the SnO2 sensor from ethanol to hydrogen, but also significantly improved the gas sensitivity and reduced the working temperature. And the optimal 1.0%Pd/SnO2 sensor owned the highest sensitivity (75), fastest response-recovery property (21 s/13 s) to 20 ppm of hydrogen at 220 °C, and the actual detection limit is as low as 0.1 ppm. Furthermore, 1.0%Pd/SnO2 sensor exhibited excellent repeatability, reproducibility and acceptable anti-interference of humidity. The DFT studies suggest that the physisorption of the hydrogen molecules on the surface of SnO2, but chemisorption on the surface of Pd/SnO2. The improved H2 sensing performance of Pd/SnO2 sensor attributes its ultrathin thickness of SnO2 and catalytic dissociation of Pd to O2 and H2.