Division of Chemistry & Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371 (Singapore), Fax: (+65) 6791-1961.
Chemistry. 2013 Sep 16;19(38):12673-83. doi: 10.1002/chem.201301889. Epub 2013 Aug 9.
Graphene and graphene oxides are materials of significant interest in electrochemical devices such as supercapacitors, batteries, fuel cells, and sensors. Graphene oxides and reduced graphenes are typically prepared by oxidizing graphite in strong mineral acid mixtures with chlorate (Staudenmaier, Hofmann) or permanganate (Hummers, Tour) oxidants. Herein, we reveal that graphene oxides pose inherent electrochemistry, that is, they can be oxidized or reduced at relatively mild potentials (within the range ±1 V) that are lower than typical battery potentials. This inherent electrochemistry of graphene differs dramatically from that of the used oxidants. Graphene oxides prepared using chlorate exhibit chemically irreversible reductions, whereas graphene oxides prepared through permanganate-based methods exhibit very unusual inherent chemically reversible electrochemistry of oxygen-containing groups. Insight into the electrochemical behaviour was obtained through cyclic voltammetry, chronoamperometry, and X-ray photoelectron spectroscopy experiments. Our findings are of extreme importance for the electrochemistry community as they reveal that electrode materials undergo cyclic changes in charge/discharge cycles, which has strong implications for energy-storage and sensing devices.
石墨烯和氧化石墨烯是电化学器件（如超级电容器、电池、燃料电池和传感器）中具有重要意义的材料。氧化石墨烯和还原石墨烯通常通过在强矿酸混合物中用氯酸盐（斯塔登迈尔，霍夫曼）或高锰酸盐（Hummers，Tour）氧化剂氧化石墨来制备。在此，我们揭示了氧化石墨烯具有固有的电化学性质，即在比典型电池电势低的相对温和的电势（在±1 V 范围内）下可以被氧化或还原。这与所用氧化剂的石墨烯的电化学性质有很大的不同。使用氯酸盐制备的氧化石墨烯表现出化学不可逆的还原，而通过高锰酸盐方法制备的氧化石墨烯表现出非常不寻常的含氧基团的固有化学可逆电化学性质。通过循环伏安法、计时安培法和 X 射线光电子能谱实验获得了对电化学行为的深入了解。我们的发现对电化学界具有极其重要的意义，因为它们揭示了电极材料在充放电循环中经历循环的电荷/放电变化，这对储能和传感设备具有很强的影响。
