The burgeoning interest in single atom catalysts (SACs) stems from their exceptional oxidase-mimicking capabilities, driving substantial advancements in this field. Nevertheless, a critical knowledge gap remains regarding the influence of Zn incorporation on the oxidase-like activity of atomically dispersed Fe-N-C catalysts. This study successfully synthesized and comprehensively characterized three distinct SACs (FeZn SAC-N@C, Fe SAC-N@C, and Zn SAC-N@C) using TEM, HAADF-STEM, XRD, XPS, BET, ICP-MS, and XAFS techniques. Activity assays revealed that FeZn SAC-N@C exhibited the highest oxidase-mimicking activity, with Fe SAC-N@C displaying moderate activity, whereas Zn SAC-N@C did not exhibit oxidase-like behavior. The superior oxidase-like activity of FeZn SAC-N@C is attributed to its enhanced O 2 activation capacity, characterized by a high free energy of 0.90 eV in the rate-determining reaction step, surpassing those of Fe SAC-N@C (0.85 eV) and Zn SAC-N@C (0.71 eV). EPR and DFT calculations elucidated the catalytic mechanism of FeZn SAC-N@C, involving the generation of O 2 − radicals. As a proof-of-concept, FeZn SAC-N@C demonstrates potential as a colorimetric sensor for detecting ascorbic acid and nitrite, achieving a limit of detection of 0.77 μM for ascorbic acid and 0.16 μM for nitrite. These findings open a new avenue for configuring bimetallic atomically dispersed catalysts with oxidase-like activity in future research.
Jianbo Wang,Jianteng Yan,Qingyan Cui,Tiesen Li,Jie Shi,Tinghai Wang,Yuanyuan Yue,Xiaojun Bao
In order to gain insight into the influence of SiO 2 support particle size on the vacuum residue (VR) slurry-phase hydrocracking performance of Fe-based catalysts, a series of FeZn/SiO 2 catalysts with varying SiO 2 particle sizes were prepared. Characterization results show that the surface area and pore volume of the FeZn/SiO 2 catalysts increase with the reduction of SiO 2 particle sizes. The metals Fe and Zn species on FeZn/SiO 2 -S catalyst are more readily reducible via H 2 -TPR analysis. Notably, FeZn/SiO 2 -S catalyst presents higher metal dispersion and a greater degree of sulfurization compared to the other catalysts by XRD and XPS characterizations. Hydrocracking results demonstrate that the FeZn/SiO 2 -S catalyst achieves the lowest coke and gas yields (11.9 wt% and 0.4 wt%), respectively, and the highest VR conversion among these catalysts. The superior performance of the FeZn/SiO 2 -S catalyst in VR slurry-phase hydrocracking is ascribed to its enhanced hydrogenation activity, deriving from the higher dispersion and sulfurization of metals species. This suppressed the aggregation of polycyclic aromatic hydrocarbons in VR and the over-cracking of intermediate products. Additionally, the increased mesopore associated with smaller SiO 2 particles facilitates to the diffusion of large VR molecules, further promoting the hydrocracking reaction.
Generally, incorporating different metals in a catalyst can provide a synergistic effect for enhancing the catalytic performance. However, the interaction between the two metals and the effect on the catalytic performance seem elusive. In this work, a bimetallic metal–organic framework (MOF) is synthesized, and then, a novel bimetallic catalyst is prepared for Fischer–Tropsch synthesis (FTS). The combination of these different metals and a MOF-derived porous carbon supporter offers a unique active surface structure that may lead to improved catalytic performance. Herein, alloy-type structures were observed in FeCo and FeNi bimetallic MOF-derived catalysts, while a solid solution with a spinel structure were observed in FeMn and FeZn bimetallic MOF-derived catalysts. The bimetallic catalysts supported on MOF-derived porous carbon display stable and excellent catalytic performance during 100 h compared with a single-metal Fe catalyst. X-ray diffraction measurement, X-ray photoelectron spectroscopy, and H2 temperature-programed reduction were employed to study the synergistic effect of bimetallic components on surface composition and electronic and reduction properties accordingly. The relationship between catalytic performance and catalyst composition was deeply studied. These research work results will provide a new approach to design novel bimetallic FT catalysts.
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