Qikai Ren,Shuaishuai Wang,Haoyu Liu,Xing Zhang,Yanran Cui,Gui-Rong Zhang,Lei Nie,Donghai Mei
The dry reforming of methane (DRM) serves as a pivotal reaction for hydrogen generation and the simultaneous conversion of methane and carbon dioxide, two major greenhouse gases, into syngas that can further be converted into high-value fuels and chemicals. However, catalyst deactivation imposes a major challenge that prohibits the market penetration of DRM. Here we reported a series of bifunctional Ni-Ce catalysts supported on SSZ-13 (Ni-Ce-SSZ-13) and discovered that a small amount of Ce could significantly enhance the activity, selectivity, and stability for DRM. Optimal ratio of Ni to Ce has been identified to yield peak catalytic performance. The optimal performance is correlated with the maximum Ce 3+ /Ce 4+ ratio as revealed by XPS analysis, which implies an increased presence of oxygen vacancies in the catalysts. It played a crucial role in facilitating the oxidation of activated CH 4 species at Ni sites, thereby enhancing DRM activity and diminishing the detrimental coke formation. It is also disclosed that integrating proper amount of Ce fosters its interactions with Ni, effectively preventing the agglomeration of Ni sites. This work presents great implications for the rational design and catalytic synergy of bi-/multi-functional zeolite catalysts for other technological applications.
Yang Fei,Wu Xiaohong,Li Chen,Chen Yuxiao,Liu Shu,Zhang Cuiling,Xian Yuezhong
A new coordination polymer (Ce-Fe-GMP) with excellent catalytic activity was prepared by a facile route, which was further applied to the detection of F − with high sensitivity and selectivity. The simple doping of Fe 3+ into the coordination network can easily modulate the mixing ratio of Ce 3+ and Ce 4+ in the presence of H 2 O 2 , which can extremely improve the catalytic ability of Ce-Fe-GMP. Based on the synergistic effect, the Ce-Fe-GMP with dual-active sites shows better peroxidase activity than that of Ce-GMP. In addition, we found that F − can inhibit the peroxidase activity of Ce-Fe-GMP because of the coordination structure fragmentation and the regulation of Ce 3+ /Ce 4+ ratio. Therefore, different concentrations of F − can be detected by the colorimetric reaction based on this mechanism. The absorption at 652 nm displays a good linear relationship versus the concentration of F − over the range 2.0 to 100.0 μM. Furthermore, F − in real mineral-mixed samples can be measured with satisfactory results. The colorimetric strategy based on the peroxidase activity of Ce-Fe-GMP is simple and low-cost, which shows the potential applications in the field of on-site environment measurement. Graphical abstract
Although ceria-based catalysts serve as an appealing alternative to traditional V2O5-based catalysts for selective catalytic reduction (SCR) of NOx with NH3, the inevitable deactivation caused by SO2 at low temperatures severely hampers the ceria-based catalysts to efficiently control NOx emissions from SO2-containing stack gases. Here, we rationally design a strong sulfur-resistant ceria-based catalyst by tuning the electronic structures of ceria highly dispersed on acidic MoO3 surfaces. By using Ce L3-edge X-ray absorption near edge structure spectra in conjunction with various surface and bulk structural characterizations, we report that the sulfur resistance of the catalysts is closely associated with the electronic states of ceria, particularly expressed by the Ce3+/Ce4+ ratio related to the size of the ceria particles. As the Ce3+/Ce4+ ratio increases up to or over 50%, corresponding to CeO2/MoO3(x %, x ≤ 2.1) with the particle size of approximately 4 nm or less, the non-bulk electronic states of ceria appear, where the catalysts start to show strong sulfur resistance. This work could provide a new strategy for designing sulfur-resistant ceria-based SCR catalysts for controlling NOx emissions at low temperatures.
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