Guohui Cai

Synthesis of highly dispersed ceria–zirconia supported on ordered mesoporous alumina

Highly dispersed ceria-zirconia supported on ordered mesoporous alumina, showing higher thermal stability up to 900 °C, has been successfully synthesized via a sol-gel process associated with P123 as the template in ethanol solvent.

Highly efficient Pd/Al2O3-Ce0.6Zr0.4O2 catalyst pretreated by H2 for low-temperature methanol oxidation

We report an interesting finding that the catalytic performance of Pd/Al2O3-Ce0.6Zr0.4O2 catalyst toward complete oxidation of methanol at low temperature could be greatly enhanced by prereduction in hydrogen. The light-off temperature (T50) could be reached rapidly at 67 °C. TPR patterns showed that the reducibility is highly increased due to the formation of stronger interactions between PdOx and CeO2 after hydrogen pretreatment. It was confirmed by XPS analysis, and the generation of higher charged Pdδ+ (δ > 2) species were discovered. As a result, it was induced that the presence of stronger interactions between PdOx and CeO2 after prereduction mainly contributes to the remarkably enhanced activity.

Sulfur Resistance and Activity of Pt/CeO2-ZrO2-La2O3 Diesel Oxidation Catalysts

Three Pt/CeO2-ZrO2-La2O3 diesel oxidation catalysts were prepared by two different routes and characterized by X-ray diffraction, N2 adsorption, temperature-programmed reduction, temperature-programmed desorption, X-ray photoelectron spectroscopy, and infrared spectroscopy. The synthesis procedure affected the structure, texture, sulfur resistance, and catalytic activity of the catalysts. Sulfur poisoning increased the light-off temperature of all the catalysts, but the Pt/CeO2-ZrO2-La2O3 catalyst prepared by depositing ZrO2 and La2O3 on the surface of CeO2 nanoparticles exhibited better sulfur tolerance and catalytic activity with simulated diesel emission due to the high dispersion of Pt on CeO2-ZrO2-La2O3 oxide with a Zr-rich surface.

A GdAlO3 Perovskite Oxide Electrolyte-Based NOx Solid-State Sensor.

NOx is a notorious emission from motor vehicles and chemical factories as the precursor of acid rain and photochemical smog. Although zirconia-based NOx sensors have been developed and showed high sensitivity and selectivity at a high temperature of above 800 °C, they fail to show good performance, and even don’t work at the typical work temperature window of the automotive engine (<500 °C). It still is a formidable challenge for development of mild-temperature NOx detector or sensor. Herein, a novel amperometric solid-state NOx sensor was developed using perovskite-type oxide Gd1−xCaxAlO3−δ(GCA) as the electrolyte and NiO as the sensing electrode. NOx sensing properties of the device were investigated at the temperature region of 400–500 °C. The response current value at −300 mV was almost linearly proportional to the NOx concentration between 300 and 500 ppm at 500 °C. At such a temperature, the optimal sensor gave the highest NO2 sensitivity of 20.15 nA/ppm, and the maximum response current value reached 5.57 μA. Furthermore, a 90% response and 90% recover time to 500 ppm NO2 were about 119 and 92 s, respectively. The excellent selectivity and stability towards NOx sensing showed the potential application of the sensor in motor vehicles.

A Novel Highly Sensitive NO 2 Sensor Based on Perovskite Na 0.5+x Bi 0.5 TiO 3−δ Electrolyte

NOx is one of dangerous air pollutants, and the demands for reliable sensors to detect NOx are extremely urgent recently. Conventional fluorite-phase YSZ used for NOx sensor requires higher operating temperature to obtain desirable oxygen ion conductivity. In this work, perovskite-phase Na0.5Bi0.5TiO3 (NBT) oxygen conductor was chosen as the solid electrolyte to fabricate a novel highly sensitive NO2 sensor with CuO as the sensing electrode and Pt as reference electrode. Na dopped Na0.5Bi0.5TiO3 greatly improved the sensing performance of this sensor. The optimal sensor based on Na0.51Bi0.50TiO3−δ exhibited good response-recovery characteristics to NO2 and the response current values were almost linear to NO2 concentrations in the range of 50–500 ppm at 400–600 °C. The response current value towards NO2 reached maximum 11.23 μA at 575 °C and the value on NO2 is much higher than other gases (CH4, C2H4, C3H6, C3H8, CO), indicating good selectivity for detecting NO2. The response signals of the sensor were slightly affected by coexistent O2 varying from 2 to 21 vol% at 575 °C. The response current value decreased only 4.9% over 2 months, exhibiting the potential application in motor vehicles.