Liu Shuang, Huang Yan, Li Shanshan, Lin Qingjin, Wang Jianli, Xie Shaohua, Liu Fudong, Xu Haidi, Chen Yaoqiang
Institute of New Energy and Low-Carbon Technology, Sichuan University, Chengdu 610207, Sichuan, China.
Sichuan Provincial Environmental Protection Environmental Catalytic Materials Engineering Technology Center, College of Chemistry, Sichuan University, Chengdu 610064, Sichuan, China.
Environ Sci Technol. 2023 Oct 31;57(43):16685-16694. doi: 10.1021/acs.est.3c05384. Epub 2023 Oct 21.
Selective catalytic reduction of NO by NH (NH-SCR) for diesel emission control at low temperatures is still a great challenge due to the limit of the urea injection threshold and inferior SCR activity of state-of-the-art catalyst systems below 200 °C. Fabricating bifunctional catalysts with both low temperature NO adsorption-storage capacity and medium-high temperature NO reduction activity is an effective strategy to solve the issues mentioned above but is rarely investigated. Herein, the WO/CeZrO (W/CZ) catalyst containing the CeZrO pyrochlore structure was successfully developed by a simple H reduction method, not only showing superior NO adsorption-storage ability below 180 °C but also exhibiting excellent NH-SCR activity above 180 °C. The presence of the pyrochlore structure effectively increased the oxygen vacancies on the CeZrO-containing W/CZ catalyst with enhanced redox property, which significantly promoted the NO adsorption-storage as active nitrate species below 180 °C. Upon NH introduction above 180 °C, the CeZrO-containing W/CZ catalyst showed greatly improved NO reduction performance, suggesting that the pyrochlore structure played a vital role in improving the NO adsorption-selective catalytic reduction (AdSCR) performance. This work provides a new perspective for designing bifunctional CeZrO-based catalysts to efficiently control the NO emissions from diesel engines during the cold-start process.
由于尿素喷射阈值的限制以及现有催化剂体系在200℃以下的选择性催化还原（SCR）活性较差，通过氨（NH₃-SCR）选择性催化还原NO以控制柴油发动机低温排放仍然是一个巨大的挑战。制备具有低温NO吸附存储能力和中高温NO还原活性的双功能催化剂是解决上述问题的有效策略，但很少有人对此进行研究。在此，通过简单的H₂还原方法成功开发了含有CeZrO₂烧绿石结构的WO₃/CeZrO₂（W/CZ）催化剂，该催化剂不仅在180℃以下表现出优异的NO吸附存储能力，而且在180℃以上表现出优异的NH₃-SCR活性。烧绿石结构的存在有效地增加了含CeZrO₂的W/CZ催化剂上的氧空位，增强了其氧化还原性能，这显著促进了180℃以下作为活性硝酸盐物种的NO吸附存储。在180℃以上引入NH₃后，含CeZrO₂的W/CZ催化剂的NO还原性能有了很大提高，这表明烧绿石结构在改善NO吸附-选择性催化还原（AdSCR）性能方面起着至关重要的作用。这项工作为设计双功能CeZrO₂基催化剂以有效控制柴油发动机冷启动过程中的NO排放提供了新的视角。
