微波固相法合成掺杂石墨烯担载钯钨合金催化剂及其在锂空气电池中的性能研究

发布时间：2018-03-04 11:37

本文选题：微波辅助加热　切入点：电催化剂　出处：《深圳大学》2017年硕士论文　论文类型：学位论文

【摘要】：石油资源的日益匮乏和温室气体排放所引起的地球暖化的加剧,使绿色环保的新型能源与技术的开发和利用成为十分迫切需要研究的课题。有机体系锂空气电池因具有巨大的比容量而有着重要的应用前景。空气电极是电池反应的主要场所,不仅提高电极反应(氧还原和氧析出反应)效率,而且可降低电极过电位,所以提高电池的能量效率和循环性能已经成为了有机体系锂空气电池发展和应用的过程中亟待解决的关键问题。研究表明,在电池正极中加入合适的电催化剂能够有效地降低电化学反应极化,提高电池充放电与循环性能。石墨烯材料具有结构规整、制备可控等优点,不但可以作为载体来制备担载型电催化剂,而且还可以作为一个理想的模型体系来研究担载型催化剂的活性、稳定性及催化机理等。(1)采用微波辐射技术,将氧化石墨烯与固相硫源及氮硫源的混合物加热,一步实现氧化石墨烯的还原及异质原子的掺杂。实验结果表明,通过微波加热能够在很短的时间内制备出掺杂的石墨烯,异质原子掺杂后石墨烯的(002)衍射峰发生了偏移,其强度也随着氮硫前驱体加入量的增加而逐渐增强。石墨烯掺杂前后的形貌并无大的变化,说明采用固相法也能够得到比表面积大、层数较少的石墨烯,而掺杂后石墨烯中缺陷度有所增加,当氧化石墨与硫脲的质量比为3:1时,其拉曼谱图的D峰与G峰的强度比约为0.99,大于未掺杂石墨烯(0.81),此时掺杂石墨烯表现出最好的氧还原催化活性。利用微波加热与化学还原相结合,可以在短时间内还原合金并负载在掺杂或未掺杂石墨烯上。结果发现,当钯钨物质的量之比为3:1,且钯钨合金负载在石墨烯上的量为20%时,表现出最优的催化性能。(2)采用微波辅助与化学还原相结合方法制备硫掺杂石墨烯担载钯钨合金(Pd3W-SG)电催化剂。实验表明:1、合成的钯钨合金杂质相少、结晶度高,并且合金颗粒均匀分散在硫掺杂石墨烯表面;2、在碱性电解液中进行氧还原反应(ORR)循环伏安(CV)测试,Pd3W-SG相对于其他样品来说,表现出更正的起始电位(-0.02 V),而其它样品起始电位分别为Pd-SG(-0.12 V)、Pd-G(-0.12 V)、SG(-0.19 V)与G(-0.21 V),表明掺杂石墨烯担载钯钨合金电催化剂具有更高的ORR催化活性。3、旋转圆盘电极(RDE)与旋转环盘电极(RRDE)测试中,该电催化剂表现出接近4的转移电子数,与商业铂碳(Pt/C)催化剂相当;4、Pd3W-SG与商业Pt/C的抗毒化性测试中,在加入甲醇后其电流密度仅改变0.04706 mA/cm2,而商业铂碳则改变0.09094mA/cm2;5、Pd3W-SG与商业Pt/C的稳定性测试中,Pd3W-SG的峰值电位电流密度仅改变0.01854 mA/cm2,而铂碳则改变0.07669 mA/cm2;6、在放电电流密度为100 mA/g时,使用Pd3W-SG催化剂为正极的锂空气电池具有更高的比容量(5660.8 mAh/g)及循环寿命。(3)采用微波辅助与化学还原相结合方法制备了氮硫掺杂石墨烯担载钯钨合金(Pd3W-NSG)样品。实验表明:1、掺杂石墨烯中引入的异质原子或缺陷能够改善担载颗粒的生长,使钯钨合金颗粒能够匀分散在NSG上;2、Pd-G、Pd-NSG与Pd3W-NSG样品的合金颗粒大小分别为14.33、32.8及20.3 nm,小尺寸的纳米颗粒具有更大的比表面积,能够有效提高催化剂的电化学反应活性面积,从而提高其催化活性;3、在碱性条件下进行ORR的CV测试,Pd3W-NSG表现出比其他样品更正的起始电位(-0.014 V),而其它样品分别为Pd-NSG(-0.126 V)、Pd-G(-0.143 V)、NSG(-0.187 V)与G(-0.204V)。RDE与RRDE测试,Pd3W-NSG电催化剂表现出接近4的转移电子数;4、进行抗毒化性测试时,Pd3W-NSG表现出比商业Pt/C要强的耐毒化性,加入甲醇后Pt/C的电流密变化比Pd3W-NSG要高0.06592 mA/cm2;5、进行10000次的CV循环稳定性测试时,Pd3W-NSG的峰值电位电流密度只改变了0.01819 mA/cm2;6、在放电电流密度为100 mA/g时,使用Pd3W-NSG催化剂正极的锂空气电池表现出高的比容量(7441.1mAh/g);这些结果都证明Pd3W-NSG具有降低氧还原活化能及锂空气电池中充电产物分解活化能,从而提高电极反应催化性能的作用;7、进行扫描电化学显微镜(SECM)测试中,Pd3W-NSG表现出最高的催化活性。
[Abstract]:The growing shortage of oil resources and greenhouse gas emissions caused by global warming intensifies, the development of new energy technology and green environmental protection and utilization is an urgent need to study. The organic system lithium air battery because of its huge capacity and have important application prospect. The air electrode is the main place for cell reaction that not only improve the electrode reaction (reduction of oxygen and oxygen evolution reaction) efficiency, but also reduce the overpotential, so to improve the energy efficiency and the cycle performance of the battery has become the key problem to be solved in the process of organic system lithium air battery development and application. The results show that adding suitable catalysts in battery anode can effectively reduce the electrochemical polarization, improve the battery charge and discharge cycle performance. The graphene material has a regular structure, controllable preparation etc., but can not As a carrier for the preparation of supported catalysts, but also can be used as an ideal model system to study the supported catalyst activity, stability and catalytic mechanism. (1) using the technique of microwave radiation, graphene oxide and solid sulfur sources and sulfur and nitrogen source mixture heating step to achieve reduction of graphene oxide and hetero atoms. The experimental results show that the prepared graphene doped in a very short period of time can be heated by microwave, the graphene doped (002) after the shift of diffraction peaks, the intensity is increased with the amount of nitrogen and sulfur precursor increases there is no change. The morphology of graphene doped before and after the show by solid state method can obtain a large surface area, the graphene layers less, and doped in graphene defects increased, when the graphite oxide and thiourea mass ratio was 3:1, The ratio of the intensity of the Raman spectrum of D peak and G peak figure of 0.99, higher than the undoped graphene (0.81), the doped graphene exhibits the best catalytic activity for oxygen reduction. The use of microwave heating and chemical reduction combined with alloy can be reduced in a short period of time and load in doped or undoped graphene. The results showed that when the molar ratio of tungsten palladium and palladium tungsten alloy is 3:1, load on the Shi Moxi quantity was 20%, showed the optimal catalytic performance. (2) by microwave assisted chemical reduction combined with preparation method of sulfur doped graphene supported palladium tungsten alloy (Pd3W-SG) catalysts the experiment shows: 1. The synthesis of palladium, tungsten alloy impurity phase, high crystallinity, and alloy particles uniformly dispersed in the sulfur doped graphene surface; 2 of the oxygen reduction reaction in alkaline electrolyte (ORR) cyclic voltammetry (CV) test, Pd3W-SG compared to the other samples, showing more The initial potential positive (-0.02 V), while the other samples were Pd-SG (-0.12 initial potential V), Pd-G (-0.12 V), SG (-0.19 V) and G (-0.21 V), showed that doped graphene supported palladium tungsten alloy electrocatalyst has higher catalytic activity of ORR.3, a rotating disc electrode (RDE) and rotating ring disk electrode (RRDE) test, the electro catalyst showed near the number of electron transfer 4, and commercial carbon platinum (Pt/C) catalyst; 4, test of Pd3W-SG and anti drug commercial Pt/C, the current density in methanol after changing only 0.04706 mA/cm2, while the commercial platinum carbon changing 0.09094mA/cm2; 5, the stability test of Pd3W-SG and commercial Pt/C, the peak potential Pd3W-SG current density change only 0.01854 mA/cm2, and 0.07669 mA/cm2 platinum carbon change; 6, the discharge current density of 100 mA/g, using Pd3W-SG as catalyst is the lithium air battery has higher specific capacity (5660.8 mAh/ G) and cycle life. (3) by microwave assisted chemical reduction method and combination of nitrogen and sulfur doped graphene supported palladium tungsten alloy prepared (Pd3W-NSG) samples. Experimental results show that: 1, the introduction of doped graphene in heterogeneous atoms or defects can improve the loading of particle growth, the palladium particles of tungsten alloy can be evenly dispersed in NSG; 2, Pd-G, Pd-NSG and Pd3W-NSG alloy particle size samples were 14.33,32.8 and 20.3 nm, the small size of the nanoparticles has larger specific surface area, can effectively improve the electrochemical active area of catalyst, so as to improve its catalytic activity; 3, ORR CV test in alkaline under the condition of Pd3W-NSG showed the initial potential than other samples (-0.014, V) corrections and other samples were Pd-NSG (-0.126 V), Pd-G (-0.143 V), NSG (-0.187 V) and G (-0.204V).RDE and RRDE test, Pd3W-NSG electrocatalyst showed near transfer electric 4 Number 4, of antivenom; test, Pd3W-NSG showed stronger resistance to poisoning than commercial Pt/C, methanol Pt/C after current density variation is 0.06592 higher than the Pd3W-NSG mA/cm2; 5, CV test cycle stability 10000 times, the peak potential current density Pd3W-NSG only changed 0.01819 mA/cm2; 6 in the discharge, the current density is 100 mA/g, using the Pd3W-NSG catalyst electrode of lithium air battery shows high specific capacity (7441.1mAh/g); these results show that Pd3W-NSG can reduce the activation energy for oxygen reduction and lithium air battery charging product decomposition activation energy, so as to improve the catalytic performance of electrode reaction; 7, scanning electrochemical microscope (SECM) test, Pd3W-NSG exhibited the highest catalytic activity.

【学位授予单位】：深圳大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;TM912

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