Microwave Intercalation Synthesis of WO3 Nanoplates and Their NO-Sensing Properties

Tungsten(VI) oxide (WO3) nanoplates were successfully synthesized by microwave intercalation. Through microwave processing, an intermediate product H2W2O7·xH2O was prepared quickly to greatly decrease the time used to prepare WO3 nanoplates. The crystal structure and morphology of WO3 were characterized by x-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, and selected-area electron diffraction. The morphology of WO3 changed with an increase in calcining temperature. A mixed-potential NO x sensor using planar yttria-stabilized zirconia and WO3 as the sensing electrode (SE) was fabricated, and its performance in NO x detection at high temperature was examined. It was determined that at 500 °C, the sensor with the WO3-nanoplate SE had higher sensitivity to NO than the sensor with a SE consisting of WO3 microparticles. The response of the NO sensor with a WO3-nanoplate SE was linear with the logarithm of NO concentration in the range of 100-1000 ppm. The electrochemical impedance measurements indicate that the electrode reaction that occurred at the triple-phase boundary (TPB) of the sensor with WO3-nanoplate SE was stronger than the reaction that occurred at the TPB of the sensor with WO3-microparticle sensing electrode.