Room-Temperature Selective Detection of H₂ by Pd Nanoparticle-Decorated SnO₂@WO₃ Core-Shell Hollow Structures

Sensitive H₂ sensors play key roles in the large-scale and safe applications of H₂. In this study, we developed novel ternary Pd-loaded SnO₂@WO₃ core-shell structures by hydrothermal and in situ reduction methods. The compositions of the optimized ternary core-shell structures (Pd-SW-2) are prepared on the basis of the optimal binary core-shell structures (SW-X) according to the sensing performances to H₂. Gas sensing tests reveal that the sensing performances (e.g., sensing response and response/recovery time) to H₂ are gradually improved after the formation of core-shell structures and the modification of Pd nanoparticles. 10Pd-SW-2 exhibits the highest response (370 times and 204 times higher than those of SnO₂ and SW-2, respectively) and the shortest response and recovery time (19/53 s) to 100 ppm of H₂ at 25 °C among the as-prepared ternary and binary composites. Combined with the morphology, XPS, electrochemical, H₂-TPR, and O₂-TPD analyses, the underlying reasons for the improved sensing performance of 10Pd-SW-2 are attributed to (1) the unique core-shell hollow structure and appropriate Pd particle sizes and distribution, (2) abundant oxygen vacancies, (3) the electron sensitization resulting from the energy band structure, and (4) the excellent chemical sensitization originated from the interaction between Pd/PdHx/PdO and H₂.