Liyun Huang,Kui Wu,Qian He,Chao Xiong,Tao Gan,Xiaohui He,Hongbing Ji
Single atom catalysts (SACs), featured with atomically dispersed metal species, have been considered as one of the most promising catalytic materials because of the excellent performance in various high-value-added reactions. However, the large-scale and continuous-type production of such SACs is still challenging. Herein, a novel and facile microcapsule strategy for the quasi-continuous synthesis of iron SACs supported on S, N co-doped carbon (Fe/SNC) is developed, and the Fe species are presented as isolated active sites and stabilized as the FeN 3 S-like structure. The as-prepared Fe/SNC catalysts exhibit excellent catalytic properties for selective oxidation of arylalkanes, which followed pseudo-first-order kinetics with an E a = 41.5 kJ/mol. More importantly, the two Fe/SNC catalysts synthesized at different continuous times showed essentially identical catalyst structure and catalytic performance, demonstrating the superior reliability of our microcapsule strategy for the quasi-continuous production of SACs, which can be easily scaled up to industrial application.
The poor performance and severe metal leaching of iron-based Fenton-like catalysts during reaction are the main bottlenecks that suppress their practical applications. Herein, a well-defined structure was achieved by confining catalytically active but unstable sulfur-containing iron species within S/N co-doped porous carbon (Fe-S@SNC) through a simple pyrolysis route. The hierarchically porous and highly conductive carbon host not only provided abundant exposed active sites and fast mass/electron-transfer, but also prohibited the aggregation of iron composites during catalysis. The synergistic effects of confined iron nano-composites and heteroatoms (S/N) significantly elevated the activation of peroxymonosulfate (PMS). As a result, the Fe-S@SNC/PMS system exhibited excellent catalytic degradation performance for various contaminants including dyes, phenolic compounds, and antibiotics. Importantly, a low iron leaching was detected during usage due to the nano-confinement effect of carbon layers, and therefore solves the long-term issue of secondary pollution caused by metal leaching. Furthermore, the underlying degradation mechanism of Fe-S@SNC/PMS system was systematically investigated by radical quenching tests, EPR analysis, and chronoamperometry experiments. It was found that the superoxide anion radical (O 2 − ) was the predominant free radicals that contributed to the radical oxidation of organic pollutants, while the electron transfer mediation on Fe-S@SNC resulted in the non-radical oxidation. Additionally, the LC-MS results coupled with time-dependent HPLC spectra validated that the degradation efficiency and intermediate products were significantly dependent on solution pH and background species. This work provides new insight into the design and activation mechanism of iron-based PMS activators.
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