电弧放电法制备石墨烯的硝酸改性及其电化学性能增强

采用电弧放电法大规模制备了层数少, 导电率高, 结晶性好的石墨烯纳米片(GNSs). 通过扫描电镜(SEM)和透射电镜(TEM)表征发现制得的石墨烯形貌良好. 然而电化学测试表明GNSs作为电极材料的电容性能不好. 为了增加材料表面电化学反应活性点, 促进GNSs在水系电解液中的润湿性, 我们对所制备的GNSs表面进行了硝酸改性处理. 结果显示硝酸处理后的石墨烯纳米片(H-GNSs)表面新增了较多的含氧氮官能团,其亲水性得到了显著提高. 对H-GNSs的电化学研究表明: 硝酸改性处理后的GNSs在2 mol·L^-1 KOH溶液中电流密度为0.5 A·g^-1时, 比电容可达65.5 F·g^-1, 约为改性前的30 倍; 此外, H-GNSs作为电极材料连续进行2000次充放电测试后还展示出了良好的循环稳定性, 是一种潜在的超级电容器电极材料.

Nitric Acid Modification of Graphene Nanosheets Prepared by ArcDischarge Method and Their Enhanced Electrochemical Properties

Large-scale synthesis of few-layer graphene nanosheets (GNSs) with high crystallinity and electrical conductivity (1680 S · m -1 ) is achieved by an arc-discharge method. The GNSs exhibited good morphologies as observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). However, electrochemical testing showed that the performance of the graphene (GNS) electrodes in supercapacitors was poor. To increase the surface active sites for electrochemical reactions and promote the wettability by aqueous electrolyte of the GNSs, a nitric acid treatment was used to chemically modify their surface. The acid treatment introduced more oxygen/nitrogen-containing functional groups onto the GNS surface, and clearly enhanced the hydrophilicity. The nitric-acid-modified GNSs (H-GNSs) showed vastly better electrode performance, with a maximum specific capacitance of 65.5 F · g -1 (about 30 times that of original GNSs) at a current density of 0.5 A · g -1 in 2 mol · L -1 KOH electrolyte. In addition, the H-GNS electrode showed good cycling stability and lifetime after running 2000 cycles. Therefore, H-GNSs may be an attractive candidate as electrode materials for supercapacitors.