Sprinkling MnFe2O4 quantum dots on nitrogen-doped graphene sheets: the formation mechanism and application for high-performance supercapacitor electrodes
Sprinkling MnFe2O4 quantum dots on nitrogen-doped graphene sheets: the formation mechanism and application for high-performance supercapacitor electrodes
复制标题
氮掺杂石墨烯片上喷洒MnFe2O4量子点：高性能超级电容器电极的形成机制及应用
DOI：
10.1039/c8ta02982b
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发表时间：
2018
影响因子：
11.9
通讯作者：
Yan Xingbin
中科院分区：
文献类型：
--
作者：
Su Lijun;Lei Shulai;Liu Li;Liu Lingyang;Zhang Yuefei;Shi Siqi;Yan Xingbin
量子点（QD）/石墨烯复合材料作为高性能超级电容器的有前景的电极材料很有趣，因为它们可以很好地整合量子点和石墨烯的互补特性。在此，我们展示了通过可控溶剂热合成制备的MnFe2O4量子点/氮掺杂石墨烯（NG）材料，其中超小的MnFe2O4量子点均匀地锚定在NG表面上。第一性原理计算表明，氧化石墨烯的含氧基团在产生这种结构中起着至关重要的作用，首先形成铁氧体八面体骨架，然后插入Mn原子。粉状 MnFe2O4 QDs/NG 在 KOH 电解质中的负电势窗口 (−1 ∼ 0 V) 内表现出 517 F g−2 的高比电容。当下截止电压扩展至-1.2 V时，比电容可增加至905 F g-1。而具有惊人负载质量18 mg cm−2的凝聚态MnFe2O4 QDs@NG电极（形成与火龙果片类似的结构）可以实现高面积和体积电容（5.3 F cm−2和277.6 F cm−3）。此外，碳封装有利于提高倍率和循环性能，即使在 200 A g−1 下也能实现 150 F g−1 的令人满意的电容，以及高达 65 000 次循环的优异寿命。这些结果使得此类材料与超级电容器电极具有竞争力，并可能加速用于储能应用的基于量子点的电极的开发。
Quantum dots (QDs)/graphene composites are interesting as promising electrode materials for high-performance supercapacitors because they can well integrate the complementary features of QDs and graphene. Herein, we demonstrate a MnFe2O4 QDs/nitrogen-doped graphene (NG) material prepared by a controllable solvothermal synthesis, in which ultra-small MnFe2O4 QDs are uniformly anchored on NG surfaces. First-principles calculations elucidate that the oxygen-containing groups of graphene oxide play a crucial role in generating such a structure, and a ferrite octahedral skeleton is firstly formed followed by Mn atom insertion. Powdery MnFe2O4 QDs/NG exhibits a high specific capacitance of 517 F g−2 within a negative potential window (−1 ∼ 0 V) in KOH electrolyte. When the lower cut off voltage is extended to −1.2 V, the specific capacitance can be increased to 905 F g−1. And the condensed MnFe2O4 QDs@NG electrode (forming a similar structure to pitaya slices) with an astonishing loading mass of 18 mg cm−2 can achieve high areal and volumetric capacitances (5.3 F cm−2 and 277.6 F cm−3). Moreover, carbon encapsulation is favorable for the improvement of rate and cycling performance, allowing a satisfactory capacitance of 150 F g−1 even at 200 A g−1 as well as a superior lifetime up to 65 000 cycles. These results make such materials competitive with supercapacitor electrodes and may speed up the development of QD-based electrodes for energy storage applications.