Metal

Catalysis

Engineering

Oxide

Nanoparticle

Metallurgy

Materials science

Operating temperature

Semiconductor

Chemical engineering

Nanowire

Thermodynamics

Physics

Nanotechnology

Organic chemistry

Hydrothermal circulation

Microstructure

Surface modification

Composite material

Chemistry

Selectivity

Optoelectronics

Sensors and Actuators B Chemical

The application of NO2 sensor based on metal oxide semiconductor is limited due to high operating temperature and poor selectivity. In this work, a low-temperature and high-performance NO2 sensor based on Pd-functionalized ZnO nanowires (Pd-ZNWs) prepared by a facile one-pot hydrothermal method was reported. The Pd was formed and self-assembled onto the surface of ZnO nanowires (ZNWs) during this one-pot hydrothermal process. Microstructure characterization of Pd-ZNWs indicated that the obtained ZNWs with diameter of 100–250 nm and length of 2–10 μm had a single crystal hexagonal structure, and Pd/PdO nanoparticles of approximately 2–5 nm in diameter were distributed on their surface. Gas sensing measurement showed that Pd-ZNWs exhibited higher response, lower optimal operating temperature, and faster response/recovery speeds towards NO2 than those of pure ZNWs. The maximum responses of 1 mol%, 2 mol%, and 5 mol% Pd-ZNWs towards 1 ppm NO2 were 13.5, 9.4, and 9.4, respectively, which were obtained at a low operating temperature of 100 °C and 30% RH. Pd-ZNWs also showed a significant improvement in sensing selectivity towards NO2. At a high RH condition of 60%, the sensors based on pure and Pd-ZNWs still exhibited noticeable responses, fast response/recovery speeds, and good long-term stability to NO2 gas. The sensing mechanism of Pd-ZNWs towards NO2 was discussed by the combination of electronic and chemical sensitization.

NO2 sensing properties of one-pot-synthesized ZnO nanowires with Pd functionalization