Behera Nibedita, Mantry Swarna P, Mohapatra Biswaranjan D, Behera Rajesh K, Varadwaj Kumar S K
Department of Chemistry, Ravenshaw University Cuttack Odisha 753003 India
RSC Adv. 2019 Sep 4;9(48):27945-27952. doi: 10.1039/c9ra04677a. eCollection 2019 Sep 3.
In this work, we systematically followed the growth of MnO nanostructures on trimesic acid (TMA)/benzoic acid (BA) functionalised nitrogen doped graphene (NG) and studied their electrocatalytic activity towards oxygen reduction reaction (ORR). In these hybrid materials the MnO phase, their morphology and Mn surface valency were guided by the functional molecules, their concentration and the duration of reaction, which in turn significantly affected the ORR activity. During the growth in the presence of TMA, agglomerated nanostructures were formed at 2 h reaction, which transformed to well dispersed 4-7 nm particles at 6 h over a large area of NG. However, in the presence of BA, MnOOH nano-flecks were formed at 2 h and transformed to MnOOH nanowires and oval shaped MnO particles at 8 h of reaction. The valency of surface Mn on the different MnO nanostructures was ascertained by X-ray photoelectron spectroscopy (XPS). The ORR activity of samples were studied by cyclic voltammetry (CV) and rotating disc electrode (RDE) in alkaline medium. Among all the studied samples, the highest ORR activity with most efficient 4e transfer process is observed for TMA modified NG-MnO obtained at 6 h of reaction, which is due to its well dispersed nanostructure morphology.
在这项工作中，我们系统地追踪了三嗪酸（TMA）/苯甲酸（BA）功能化氮掺杂石墨烯（NG）上MnO纳米结构的生长情况，并研究了它们对氧还原反应（ORR）的电催化活性。在这些混合材料中，MnO相、其形态和Mn表面价态受功能分子、其浓度和反应持续时间的引导，这反过来又显著影响了ORR活性。在TMA存在下生长时，反应2小时形成团聚的纳米结构，6小时时在大面积的NG上转变为分散良好的4 - 7纳米颗粒。然而，在BA存在下，反应2小时形成MnOOH纳米斑点，反应8小时时转变为MnOOH纳米线和椭圆形MnO颗粒。通过X射线光电子能谱（XPS）确定不同MnO纳米结构上表面Mn的价态。在碱性介质中，通过循环伏安法（CV）和旋转圆盘电极（RDE）研究了样品的ORR活性。在所有研究的样品中，反应6小时得到的TMA修饰的NG - MnO表现出最高的ORR活性和最有效的4e转移过程，这归因于其良好分散的纳米结构形态。
