High response and selectivity toward hydrogen gas detection by In₂O₃ doped Pd@ZnO core-shell nanoparticles

An efficient hydrogen gas sensor comprising 5 wt% In₂O₃ doped in Pd@ZnO core-shell nanoparticles (Pd@ZnO–In₂O₃ CSNPs) was synthesized via a facile hydrothermal approach. The obtained material has a higher Brunauer-Emmett-Teller surface area (80 m² g⁻¹) compared to Pd@ZnO (56 m² g⁻¹) and pure ZnO (40 m² g⁻¹). The Pd@ZnO–In₂O₃ sensor achieved the maximal response (42) to 100 ppm hydrogen at 300 °C. Whereas, Pd@ZnO and pure ZnO sensors exhibited lower responses (17 and 9) to 100 ppm hydrogen at a higher optimal temperature (350 °C). It also demonstrated faster response and recovery time (0.4 and 4.0 min) than those obtained from Pd@ZnO (1.4 and 14 min) and pure ZnO (6.0 and 18.0 min) sensors. The hydrogen sensing enhancement of Pd@ZnO–In₂O₃ materials could be largely attributed to the synergistic electronic and chemical activities of Pd, ZnO and In₂O₃ parts, and its large surface area. Especially, due to the ability to adsorb hydrogen of the core, Pd based sensors exhibited high selectivity to hydrogen with respect to Pd-free sensors.