Pd-Doping-Induced Oxygen Vacancies in One-Dimensional Tungsten Oxide Nanowires for Enhanced Acetone Gas Sensing.

Abstract

Metal oxide semiconductors (MOS) with different nanostructures have been widely used as gas sensing materials due to the tunable interface structures and properties. However, further improvement of the sensing sensitivity and selectivity is still challenging in this area. Constructing appropriate heterogeneous interface structures and oxygen vacancies is one of the important strategies to tune the sensing properties of MOS. In the present study, interfacial heterostructures in PdxW18O49 nanowires (PdxW18O49 NWs) were fabricated and manipulated by doping different Pd contents through a simple hydrothermal process. Relevant characterization proved that the structure and composition of the one-dimensional (1D) nanomaterial can be effectively changed by Pd doping. It was found that the oxygen vacancy concentration increases first with the increase of Pd content, and when the Pd content increases to 7.18% (Pd7.18%W18O49 NWs), the oxygen vacancy content reaches the maximum (52.5%). If the Pd content continues to increase, the oxygen vacancy ratio decreases. The gas sensing investigations illustrated that the PdxW18O49 NWs exhibited enhanced sensing properties than pure W18O49 NWs toward acetone. Among the as-prepared catalysts, the Pd7.18%W18O49 NWs showed the best sensing response and the fastest response-recovery speeds (5 and 10 s, respectively) at a working temperature of 175 °C. In addition, this 1D nanostructure with fabricated heterostructures also delivers a good sensing selectivity and a wide detection range from 100 ppb to 300 ppm, with maintaining excellent performance in the presence of high concentrations of ethanol and carbon dioxide. The excellent gas sensing behavior could be attributed to the generated oxygen vacancies and the heterostructures upon Pd doping. This study offers a novel strategy for the design of high-performance gas sensors for ppb-level acetone sensing.