Yi Jing Jia,Jin Quan Tao,Hao Ran Liu,Wen Bin Huang,Rongpeng Yao,Miaomiao Niu,Rongrong Li,Qiang Wei,Ya Song Zhou
To enhance the CO 2 hydrogenation activity and low-carbon olefin selectivity of Fe-based catalysts, a strategy involving the use of metal promoters to modulate the structure of active metal centers in catalyst preparation was proposed. The incipient wetness impregnation method was used to introduce modifying agents K and/or Co into the Fe/Al 2 O 3 catalyst. Characterization techniques such as XRD, BET, SEM, HRTEM, H 2 -TPR, XPS, CO 2 -TPD, NH 3 -TPD, and TG were employed to investigate the effects of the modifying agents on the dispersion, reducibility, electronic properties, and acid–base properties of active metal species. Furthermore, the influence of K and Co modification on the CO 2 hydrogenation activity and low-carbon olefin selectivity of Fe/Al 2 O 3 catalysts was explored. The results revealed that the introduction of K generated more basic sites and electron-rich active metal centers in the catalyst, facilitating the adsorption and activation of CO 2 , while suppressing the hydrogenation of olefins and the formation of methane, thus improving the selectivity towards low-carbon olefins. Co promoter facilitated the dispersion of Fe species, exposing more active sites and enhancing the FTS reaction activity, leading to more CO being converted into C 2+ hydrocarbon products. Under the synergistic effect of K and Co, the CO 2 conversion activity of the Fe-based catalyst significantly increased, achieving a CO 2 conversion rate of 37%, while the selectivity towards C 2 -C 4= increased to 31.9%.
Porous ceria nanorods modified with Fe or Co were prepared via a hydrothermal method. The structural properties, catalytic activities for the total oxidation of propane, and catalytic mechanisms of these materials were systematically investigated by X-ray diffraction, Raman spectroscopy, N 2 adsorption–desorption, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, catalytic activity measurements and in situ Fourier transform infrared spectroscopy. Co-modified ceria exhibited the best catalytic activity during propane oxidation as well as enhanced reducibility due to the synergistic interactions between the Co and the CeO 2 support. Variations in the activating ability and reducibility of the catalysts resulted in the formation of distinctive intermediates during the catalytic process, and this explained the observed differences in catalytic performance.
Improving the utilization of platinum in proton-exchange membrane (PEM) fuel cells is critical to reducing their cost. In the past decade, numerous Pt-based oxygen reduction reaction catalysts with high specific and mass activities have been developed. However, the high activities are mostly achieved in rotating disk electrode (RDE) measurement and have rarely been accomplished at the membrane electrode assembly (MEA) level. The failure of these direct translations from RDE to MEA has been well documented with several key reasons having been previously identified. One of them is the resistance caused by complex mass transport pathways in the MEA. Herein, we improve the proton and oxygen transportations in the MEA by building a thin and uniform distribution of ionomer on the catalyst surface. As a result, a PEM fuel cell design is capable of showing a current density improvement of 38% at the same voltage (0.6 V) under the H2/air operation.
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