Division of Chemistry & Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371 Singapore.
Chem Asian J. 2012 Apr;7(4):759-70. doi: 10.1002/asia.201100852. Epub 2012 Feb 1.
Graphene research is currently at the frontier of electrochemistry. Many different graphene-based materials are employed by electrochemists as electrodes in sensing and in energy-storage devices. Because the methods for their preparation are inherently different, graphene materials are expected to exhibit different electrochemical behaviors depending on the functionalities and density of defects present. Electrochemical treatment of these "chemically modified graphenes" (CMGs) represents an easy approach to alter surface functionalities and consequently tune the electrochemical performance. Herein, we report a preliminary electrochemical characterization of four common chemically modified graphenes, namely: graphene oxide, graphite oxide, chemically reduced graphene oxide, and thermally reduced graphene oxide. These CMGs were compared with graphite as a reference material. Cyclic voltammetry was used to ascertain the chemical functionalities present and to understand the potential ranges in which the materials were electroactive. Electrochemical treatment with either an oxidative or a reductive fixed potential were then carried out to activate these chemically modified graphenes. The effects of such electrochemical treatments on their electrocatalytic properties were then investigated by cyclic voltammetry in the presence of well-known redox probes, such as Fe(CN)(6), Fe(3+/2+), Ru(NH(3))(6), and ascorbic acid. Thermally reduced graphene oxide exhibited the best electrochemical behavior amongst all of the CMGs, with the fastest rate of heterogeneous electron transfer (HET) and the lowest overpotentials. These findings will have far-reaching consequences for the evaluation of different CMGs as electrode materials in electrochemical devices.
石墨烯研究目前处于电化学前沿。电化学工作者将许多不同的基于石墨烯的材料用作传感和储能器件中的电极。由于其制备方法本质上不同，因此石墨烯材料预计会根据存在的官能团和缺陷密度表现出不同的电化学行为。对这些“化学改性石墨烯”（CMGs）进行电化学处理是一种改变表面官能团并进而调整电化学性能的简便方法。在此，我们报告了对四种常见的化学改性石墨烯，即氧化石墨烯、石墨氧化物、化学还原氧化石墨烯和热还原氧化石墨烯的初步电化学表征。将这些 CMGs 与石墨作为参考材料进行了比较。使用循环伏安法确定了存在的化学官能团，并了解了材料电活性的潜在范围。然后，使用氧化性或还原性固定电势对这些化学改性石墨烯进行电化学处理，以激活它们。然后通过在存在已知氧化还原探针（如[Fe(CN)(6)]（4-/3-）、Fe（3+/2+）、[Ru(NH(3))(6)]（2+/3+）和抗坏血酸）的情况下进行循环伏安法来研究这种电化学处理对其电催化性能的影响。在所有 CMGs 中，热还原氧化石墨烯表现出最佳的电化学行为，具有最快的非均相电子转移（HET）速率和最低的过电势。这些发现对于评估电化学器件中不同 CMGs 作为电极材料的性能将具有深远的影响。
