硫氮共掺杂石墨烯的制备及其电化学性能
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摘要
采用改进的Hummers方法经冷冻干燥制备氧化石墨烯(GO),以硫脲作为还原剂和掺杂剂,按GO与硫脲的质量比为1∶10、1∶20、1∶30、1∶40的用量分别加入硫脲,采用一步水热法合成硫氮共掺杂石墨烯。通过X射线粉末衍射(XRD)、场发射扫描电子显微镜(FESEM)、拉曼光谱(Raman)、X射线光电子能谱(XPS)、氮气吸脱附分析等手段表征了样品的微观结构和形貌,通过循环伏安、电化学交流阻抗、恒流充放电技术对样品进行电化学性能测试。结果表明:当GO∶硫脲=1∶30(质量比)时,得到的硫氮共掺杂石墨烯(SNG)中硫掺杂量最高为1.86%(质量分数)、氮掺杂质量分数最高为7.73%,比表面积达175.8m2/g,且具有较窄的孔径分布,集中在3~5nm。在电流密度为1A/g时,SNG的比电容最高达197.2F/g,经过2000次充放电循环后,比电容为177.3F/g,电容保持率达90%。
The modified Hummers method was used to prepare graphite oxide(GO) through freeze drying. The sulfur-nitrogen co-doped graphene samples were then synthesized by one-step hydrothermal method using thiourea as dopant and reductant,with mass ratios of GO to thiourea of 1∶10, 1∶20, 1∶30, 1∶40 respectively. The microstructure and morphology of the as-produced graphene were characterized by X-ray diffraction, field emission scanning electron microscope, Raman spectroscopy, X-ray photoelectron spectroscopy and nitrogen adsorption-desorption analysis. The electrochemical performances of the samples were investigated by cyclic voltammetry(CV), electrochemical impedance spectroscopy(EIS) and galvanostatic charge/discharge(GCD) technology. The results showed that the sulfur-nitrogen co-doped graphene had the highest sulfur content of 1.86% and nitrogen content of 7.73%, with a specific surface area of 175.8 m2/g and the pore sizes were narrowly distributed in between 3—5 nm when the mass ratio of GO∶thiourea is 1∶30. At 1 A/g current density, SNG had a specific capacitance of 197.2 F/g, and only 10% were lost after 2000 charge and discharge cycles.
The modified Hummers method was used to prepare graphite oxide(GO) through freeze drying. The sulfur-nitrogen co-doped graphene samples were then synthesized by one-step hydrothermal method using thiourea as dopant and reductant,with mass ratios of GO to thiourea of 1∶10, 1∶20, 1∶30, 1∶40 respectively. The microstructure and morphology of the as-produced graphene were characterized by X-ray diffraction, field emission scanning electron microscope, Raman spectroscopy, X-ray photoelectron spectroscopy and nitrogen adsorption-desorption analysis. The electrochemical performances of the samples were investigated by cyclic voltammetry(CV), electrochemical impedance spectroscopy(EIS) and galvanostatic charge/discharge(GCD) technology. The results showed that the sulfur-nitrogen co-doped graphene had the highest sulfur content of 1.86% and nitrogen content of 7.73%, with a specific surface area of 175.8 m2/g and the pore sizes were narrowly distributed in between 3—5 nm when the mass ratio of GO∶thiourea is 1∶30. At 1 A/g current density, SNG had a specific capacitance of 197.2 F/g, and only 10% were lost after 2000 charge and discharge cycles.
引文
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[8]QU L,LIU Y,BAEK J B,et al.Nitrogen-doped graphene as efficient metal-free electrocatalyst for oxygen reduction in fuel cells[J].ACS Nano,2010,4(3):1321-1326.
[9]NAGAIAH T C,KUNDU S,BRON M,et al.Nitrogen-doped carbon nanotubes as a cathode catalyst for the oxygen reduction reaction in alkaline medium[J].Electrochemistry Communications,2010,12(3):338-341.
[10]PARK J,JANG Y,KIM Y,et al.Sulfur-doped graphene as a potential alternative metal-free electrocatalyst and Pt-catalyst supporting material for oxygen reduction reaction[J].Physical Chemistry Chemical Physics,2014,16:103-109.
[11]POH H,SIMEK P,SOFER Z,et al.Sulfur-doped graphene via thermal exfoliation of graphite oxide in H2S,SO2,or CS2 gas[J].ACS Nano,2013,7:5262-5272.
[12]GAO H.Synthesis of S-doped graphene by liquid precursor[J].Nanotechnology,2012,23:275-605.
[13]WANG R,HIGGINS D,HOQUE M.Controlled growth of platinum nanowire arrays on sulfur doped graphene as high performance electrocatalyst[J].Scientific Reports,2013,3:2431.
[14]GONG K,DU F,XIA Z,et al.Nitrogen-doped carbon nanotube arrays with high electrocatalytic activity for oxygen reduction[J].Science,2009,323:760-764.
[15]QU L,LIU Y,BAEK J,et al.Nitrogen-doped graphene as efficient metal-free electrocatalyst for oxygen reduction in fuel cells[J].ACS Nano,2010,4:1321-1326.
[16]LIANG J,YAN J,MIETEK J,et al.Sulfur and nitrogen dual-doped mesoporous graphene electrocatalyst for oxygen reduction with synergistically enhanced performance[J].International Edition,2012,124:11664-11668.
[17]MIAO Q H,WANG L D,LIU Z Y,et al.Magnetic properties of N-doped graphene with high Curie temperature[J].Scientific Reports,2016,6:21832.
[18]CHEN S,BI J,ZHAO Y,et al.Nitrogen-doped carbon nanocages as efficient metal-free electrocatalysts for oxygen reduction reaction[J].Advanced Materials,2012,24(41):5593-5597.
[19]CHOI C H,PARK S H,WOO S I.Binary and ternary doping of nitrogen,boron,and phosphorus into carbon for enhancing electrochemical oxygen reduction activity[J].ACS Nano,2012,6(8):7084-7091.
[20]WEHLING T,NOVOSELOV K,MOROZOV S,et al.Molecular doping of graphene[J].Nano Letters,2008,8(1):173-177.
[21]WUNSCH B,STAUBER T,SOLS F,et al.Dynamical polarization of graphene at finite doping[J].New Journal of Physics,2006,8(12):318-323.
[22]NAGAIAH T C,KUNDU S,BRON M,et al.Nitrogen-doped carbon nanotubes as a cathode catalyst for the oxygen reduction reaction in alkaline medium[J].Electrochemistry Communications,2010,12(3):338-341.
[23]XU J,DONG G,JIN C,et al.Sulfur and nitrogen co-doped,few-layered graphene oxide as a highly efficient electrocatalyst for the oxygen-reduction reaction[J].Chem.Sus.Chem.,2013,6(3):493-499.
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[26]ZHANG M Y,SUN Y Y,SHI J J,et al.Selective glycerol oxidation using platinum nanoparticles supported on multi-walled carbon nanotubes and nitrogen-doped graphene hybrid[J].Chinese Journal of Catalysis,2017,38(3):537-544.
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