N-rGO负载的α-MnO2复合材料作为铝空气电池的高效氧还原催化剂

N-rGO-supported α-MnO2 composites as Efficient Oxygen Reduction Reaction Catalyst in Aluminum-Air Battery

  • 摘要: MnO2由于其高电催化活性、环境友好、低成本、丰富的地球储量等,是碱性介质中氧还原反应(ORR)最为常见的催化剂材料之一。然而,MnO2用作ORR催化剂时往往存在着导电性较差、速率性能差和容量快速恶化等问题。基于此,本文通过将高导电的N掺杂还原石墨烯(N-rGO)作为MnO2纳米棒的良好载体,设计了一种新型N掺杂还原石墨烯负载的α-MnO2(α-MnO2@N-rGO)复合材料。通过场发射扫描电镜(FESEM)、透射电镜(TEM)、X射线衍射(XRD)、比表面积测量(BET)、X射线光电子能谱(XPS)、傅里叶红外光谱(FTIR)和拉曼光谱(Raman)对制备的α-MnO2@N-rGO复合材料进行了系统地表征。实验结果表明,水热过程后,棒状形态的MnO2均匀分散在N-rGO片上。在ORR过程中,α-MnO2@N-rGO展现出最佳的催化活性和稳定性(起始电位为0.918 V,半波电位为0.784 V,电子转移数为3.45,电流衰减率为2.16% h−1),这些相比于单一的N-rGO和α-MnO2均有明显提升。表征结果进一步证实分散良好的N-rGO与α-MnO2之间形成共价偶联作用促进α-MnO2@N-rGO催化剂催化活性和稳定性的有效提升。此外,α-MnO2@N-rGO催化剂在铝空气电池展现出优异的电化学性能(能量密度为1230.7 mW·h·g−1-Al,功率密度为135.8 mW·cm−2)和力学性能(5000次弯曲后96%以上的电流保持率)。综上所述,通过引入N-rGO来调整MnO2的电子和化学状态,并建立两种组分之间的共价界面,可为开发高效稳定的二氧化锰基ORR催化剂提供了一种有效策略。

     

    Abstract: MnO2 is one of the most common catalyst materials for oxygen reduction reaction (ORR) in alkaline media due to their high electrocatalytic activity, environmental friendliness, low cost, and abundant earth reserves. However, MnO2, as an ORR catalyst, suffered from poor conductivity, poor rate performance, and rapid capacity deterioration. Herein, a novel N-doped reduced graphene-supported α-MnO2 (α-MnO2@N-rGO) composite was designed by using highly conductive N-doped reduced graphene oxide (N-rGO) as a good carrier for MnO2 nanorods to obtain superior ORR performance. The prepared α-MnO2@N-rGO composites were systematically characterized by Field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), specific surface area measurement (BET), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy (Raman). The experimental results shows that the rod-like MnO2 is evenly dispersed on the N-rGO sheet after the hydrothermal process. In the ORR process, α-MnO2@N-rGO exhibits excellent catalytic activity and stability (onset potential of 0.918 V, half-wave potential of 0.784 V, electron transfer number of 3.45, current attenuation rate of 2.16% h−1), which are significantly improved compared with single N-rGO and α-MnO2. The characterization results further confirms that the covalent coupling between the well-dispersed N-rGO and α-MnO2 jointly promotes the effective improvement of the catalytic activity and stability of the α-MnO2@N-rGO catalyst. In addition, the α-MnO2@N-rGO catalyst displays excellent electrochemical properties (energy density of 1230.7 mW·h·g−1-Al, power density of 135.8 mW·cm−2) and mechanical properties (current retention of >96% after 5000 bending) in aluminum-air battery. In conclusion, the introduction of N-rGO to adjust the electronic and chemical states of MnO2 and establish covalent interface between the N-rGO and α-MnO2 can provide an effective strategy for the development of efficient and stable manganese dioxide-based ORR catalysts.

     

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