Ji Feng,Lin Liu,Xiaohua Ju,Qike Jiang,Jiemin Wang,Jianping Guo,Teng He,Ping Chen
Utilization of promoters to improve the catalytic performance of supported metal catalysts is an important strategy for the design of efficient catalysts. However, it is difficult to detect the relationship between the promoters and the structure of main catalysts. Herein, we firstly develop an efficient Ru-based ammonia synthesis catalyst by decorating Ru nanoparticles (NPs) on γ-alumina with sub-nanometer ceria (CeO2) species (Ce–Ru/Al2O3). In comparison with neat Ru/Al2O3, Ce–Ru/Al2O3 exhibits up to 10-fold activity enhancement at 400 °C and 1.0 MPa. Our characterization results show that such an activity increment is relevant to the function of the sub-nanometer CeO2 species on the Ru NPs. The sub-nanometer CeO2 species will aggregate around the Ru nanoparticles, leading to a clear electron transfer from sub-nanometer CeO2 species to Ru nanoparticles. At the same time, the introduction of CeO2 species can not only weaken the hydrogen poisoning effect on the Ru nanoparticles but also facilitate nitrogen adsorption and hydrogenation of dissociated N* atoms according to the kinetic test results. This work highlights the important role of highly dispersed rare earth oxide promoter species in modulating the structure and catalytic performance of supported Ru NPs for ammonia synthesis.
Xianghui Meng,Yuanjie Zhang,Zhiqiang Wang,Zihan Wang,Huiqing Zhao,Ting Wang,Zongge Li,Wenjun Kang,Haibo Li
A defect-rich carbon catalyst with highly dispersed Fe/Zn/Ce species (FeZnCe-NC-1000) is synthesized via a controllable high-temperature pyrolysis strategy. Electrochemical characterizations reveal that FeZnCe-NC-1000 exhibits enhanced oxygen reduction reaction activity in 0.1 M KOH, featuring favorable kinetics and a dominant 4-electron transfer pathway. It also shows excellent durability with minimal performance degradation after 5000 cycles and strong methanol tolerance. When integrated into zinc-air batteries, FeZnCe-NC-1000 outperforms commercial Pt/C, delivering superior open-circuit voltage, discharge rate performance, specific capacity, and maximum power density. These results demonstrate that FeZnCe-NC-1000 is a promising non-precious metal catalyst with great potential for practical applications in energy conversion and storage systems.
A core–shell catalyst composed of mCeO 2 shell and Pd metal core was prepared by one-pot wet chemical method and used for the hydrogenation of phenol to cyclohexanone. The phenol conversion and cyclohexanone selectivity were 96.3 % and 95.3 % at reaction conditions of 50 min, 80 °C and 1 MPa H 2 . The effects of Ce species and Br species in the preparation of catalysts was studied, and the synthesis mechanism of core–shell Pd@mCeO 2 catalysts was preliminarily revealed. By discussing the phenol adsorption mechanism and the redox properties of the catalyst, the activation of H 2 by Pd sites and phenol by cerium oxide (CeO 2 ) sites of the surface were studied. H 2 -TPR and XPS characterization were used to explain the effect of Ce species and Br species for the catalytic performance. These results indicated that the electronic structure of Pd was regulated by the interaction between Pd and Ce, and different O sites were generated around the Pd sites. In situ IR spectra indicated that phenol was adsorbed and dissociated on cerium to form phenoxy species and water, this synergistic catalytic pattern of carrier activated substrate and hydrogenation site promoted the hydrogenation of phenol and improved the catalytic efficiency.
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