Fang Jia,Xu Xilong,Yang Yi,Han Zhiqiang,Zuo Zinong,Han Weiqiang,Lin Bin
Effective removal of soot deposited in diesel particulate filter by catalysts has attracted great attention in the aftertreatment field to achieve environment protection, but the problem is short by incomplete and poor soot combustion. Herein, an integrated ZnO–SnO 2 semiconductor n–n heterostructure strategy of catalysts and ash is proposed for promoting diesel soot combustion. The integrated effects of different catalysts and ZnO ash on soot oxidation are studied with thermogravimetric analysis and gas emission analysis. The diesel soot is simulated by Printex U (PU) particles, and the catalysts include SnO 2 , ZrO 2 , TiO 2 , CeO 2 and Pt/Al 2 O 3 nanoparticles. Compared with other catalysts, the best catalytic effect on soot oxidation is achieved when SnO 2 catalyst is mixed with PU/ZnO at 1:1:1 mass ratio in tight contact method. The S and R w indexes reach the largest values of 9.33 × 10 –8 % 2 min −2 ℃ −3 and 38.64 × 10 5 , and the CO 2 amount reaches the maximum value at 3462 ppm, which is correspondingly with the XRD and XPS spectrum results of PU/ZnO/SnO 2 with ZnO–SnO 2 heterojunction structure having more adsorbed oxygen. The excessive catalyst is negative to the heat and oxygen transfer among the nanoparticles. When the mass ratio of PU/ZnO/SnO 2 is 1:1:1, the soot combustion presents the comparatively superior state. The results of this study innovate the soot oxidation influenced by catalyst and ash, which benefits the optimization of passive regeneration strategy in DPF application.
The development of metal oxide semiconductor-based chemiresistive gas sensors with ultra-fast response/recovery for toxic and flammable gases is of great importance, but still challenging. Here, ZnO-SnO 2 heterojunction three-dimensional (3D) inverse opal photonic crystal balls (IOPBs) were fabricated based on rapid and liquid waste-free spray drying. The spherical three-dimensional (3D) ordered macroporous skeleton can provide more active sites and faster gas diffusion channels. Furthermore, the n-n heterojunction established by ZnO and SnO 2 is favorable for electron transport . The response (Ra/Rg) of IOPBs to 50 ppm acetone reaches 40.3 at an optimal operating temperature of 260 °C when the Zn/Sn atomic ratio is 1:4, which is 5 times higher than that of the pure SnO 2 sensor. Response/recovery time also reduces from 23/47 s for pure SnO 2 to 6/10 s. In addition, the IOPBs gas sensors also exhibit good selectivity and excellent long-term stability. This work provides a straightforward and versatile synthetic route for the preparation of 3D IOPBs to explore novel gas sensors with ultra-fast response speed.
Kelin Hu,Feipeng Wang,Zijia Shen,Hongcheng Liu,Wen Zeng,Yu Wang
In this study, ZnO–SnO 2 heterojunction nanofibers were fabricated using electrospinning and treated by Ar plasma. The post treatment demonstrated the ability to regulate adsorbed oxygen of nanofibers and thus affecting the gas sensing performance. The results revealed that the gas sensing performances increased with the increase of plasma treatment time at first, then showed a downward trend. The setting for the best H 2 gas performance was 20 min of plasma treatment, under which the response of the sample was 80% higher and the response time was two thirds shorter than those of the untreated sample. The explanation can be that appropriate plasma treatment can increase the oxygen vacancy on the surface of heterojunction nanofibers as well as the resistance modulation range in the air; however, excessive plasma treatment can result in the reduction of the resistance modulation range in the air by reducing the metal oxide to metal.
危险品化学品经营许可证（带存储）