Li Fang,Qionghao Xu,Yanyan Qi,Xiaoxue Wu,Yanghe Fu,Qiang Xiao,Fumin Zhang,Weidong Zhu
The preparation of efficient and recyclable solid catalysts exhibiting high activity and selectivity toward the target product is a prerequisite to enhance the overall efficiency of a catalytic process. Herein, we study a series of Fe/Fe 3 C-containing nitrogen-doped porous carbon microspindles (Fe/Fe 3 C@NC–x, where x stands for the pyrolysis temperature), which are core-/shell-structured hybrids, constructed by the pyrolysis of a metal–organic framework precursor as highly selective catalysts for the oxidation of sulfides to the corresponding sulfoxides under mild conditions. The Fe/Fe 3 C@NC–x microspindles comprising Fe and Fe 3 C nanocrystals inlaid in nitrogen-doped porous carbon shells are fabricated by the direct carbonization of NH 2 –MIL–88B(Fe) polyhedra at 500 °C–800 °C and under nitrogen atmosphere. Among the various investigated catalysts, the Fe/Fe 3 C@NC–600 microspindles exhibit the best catalytic activity, higher than those exhibited by the analogue Fe/Fe 3 C@C–600 without N doping and the commercial Fe 2 O 3 , Fe 3 O 4 , and Fe 3 C used for the catalytic oxidation of sulfides owing to the synergistic contribution of the Fe 3 C sites and adequate nitrogen doping in the porous carbon support. Furthermore, the magnetically separable properties of the Fe/Fe 3 C@NC–600 microspindles enable their convenient isolation from the reaction system using an external magnet, and they can be repeatedly used for six cycles without any loss in catalytic efficiency.
Ternary metal oxide , such as ZnCo 2 O 4 has attracted widespread attention as electrode material for supercapacitors owing to its high theoretical activity and rich redox reactions arising from the synergistic effects between two different metal species. However, the compromised electrochemical performance due to low electronic conductivity and deficient active sites of ZnCo 2 O 4 impedes its practical applications. Herein, S-doped ZnCo 2 O 4 microspindles (denoted as S-ZnCo 2 O 4 ) have been obtained by simple hydrothermal synthesis followed by calcining and sulfurization treatments. It is indicated that the doping of S results in the formation of defects and disorders without altering the crystalline structure of ZnCo 2 O 4 , which is beneficial for charge transfer, and exposing more active sites. Taking advantage of the desired structure and composition, the S-ZnCo 2 O 4 displays superior electrochemical properties when acting as an electrode material for supercapacitors. It delivers a high specific capacity of 214.1C g −1 (522 F/g) at the current density of 0.5 A g −1 , which is almost 8.5 times that of the ZnCo 2 O 4 (25 C g −1 , 61 F/g). Moreover, the S-ZnCo 2 O 4 also shows good rate capability (82% at 10 A g −1 ) and excellent electrochemical stability (78% retention after 5000 cycles). This work demonstrates that anion doping can be an efficacious strategy of boosting electrochemical performance.
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