材料化学翻译

1、Journal of Materials Chemistry A材料化学杂志PAPERView Article OnlineView Journal | View IssueSynthesis and lithium-storage properties of MnO/ reduced graphene oxide composites derived from graphene oxide plus the transformation of Mn(VI) to Mn(II) by the reducing power of graphene oxide一氧化锰的合成和锂存储特性减少了氧化石

2、墨烯的复合材料，而后者源于氧化石墨烯以及Mn（VI)转化Mn(II)过程中，通过降低氧化石墨烯能量生出的转化物In this report, a novel method is proposed to prepare MnO/reduced graphene oxide (rGO) composites via calcining the precursors (i.e. d-MnO2/graphene oxide composites) at 500 C in Ar using no external reducing gas, in which graphene oxide (GO) su

3、ccessfully serves as a reductant by releasing CO during its thermolysis for the first time.By controlling the initial ratios of GO to KMnO4, dierently composed precursors can be obtained via the redox reaction between GO and KMnO4, then leading to the formation of composites with dierent MnO/rGO rat

4、ios and dispersion of MnO on the rGO surface (denoted as MGC1 and MGC2). When applied as an active material in lithium ion batteries, MGC1 shows excellent cycling performance and capacity retention. Under 100 and 200 mA g -1, MGC1 could deliver reversible capacities as high as 900 and 750 mA h g 1,

5、respectively, after more than 100 cycles. Considering the simple operation and low energy consumption in the whole material synthesis processes, the present strategy is feasible and eective for practical application. Even more importantly, the reductibility of graphene oxide upon thermolysis is util

6、ized for the first time, which is meaningful for its extension in synthesis of functional nanomaterials.在这份报告中，提出了制备一氧化锰/还原氧化石墨烯复合材料的一种新方法，.通过在氩气中，500 的条件下 使用没有外部的还原性气体，煅烧前驱体（i.e .d-二氧化锰/氧化石墨烯复合材料）,在此过程中，氧化石墨烯完全可以胜任还原剂的功能，首次热解，释放一氧化碳.控制氧化石墨烯（GO）和KMnO4的初始比KMnO4，通过氧化石墨烯（GO）和KMnO4氧化还原反应获得不同组成的前体，形成的复合材

7、料具有不同MnO / rGO比率和MnO，rGO表面不同的色散(用MGC1和MGC2表示)。当应用于锂离子电池的活性材料时，MGC1具有优异的循环性能和容量保持率。在100和200 mA g-1下，MGC1可以提供可逆容量高达900和750 mA h g-1 ，分别在100次以上。考虑到在整个材料合成工艺操作简单、能耗低，目前的策略是可行的和有效的实际应用。更重要的是，氧化石墨烯对热解还原是首次利用，这是其在功能纳米材料的合成延伸意义。With the increasing power and energy demand in portable electronic vehicles and

8、devices, great eort has been made in developing new high-performance electrode materials for high-power rechargeable lithium-ion batteries (LIBs).15 Transition metal oxides, such as SnO2,68 TiO2,9 MoOx,10,11 and MnO2,12,13 have been widely studied as anode materials in LIBs since rst proposed in 200

9、0 by Poizot et al.14 Among these transition metal oxides, manganese oxides (MnOx) were a promising candidate series because of their relatively low thermodynamic equilib-rium voltage versus Li/Li+,1517 and low electromotive force,1820 as well as their environmental benignity and low cost. However, t

10、here are still several drawbacks such as: (1) the large volume change and gradual agglomeration of metal grains21,22 during the discharge/charge reaction and (2) intrinsically low elec-tronic conductivity, both of which result in the rapid fading of capacities during the cycling process.23 To overco

11、me these challenges, many research studies were focused on the incor-poration of carbon nanomaterials such as carbon nano-tubes2426 and carbon nano bers27 into MnOx to suppress the pulverization and capacity fading.随着便携式电子车辆和设备对功率和能源的需求，努力开发新的高性能的电极材料为高功率可充电的锂离子电池（LIBS）。一些过渡金属氧化物，如SnO2 ，MoOx，和MnO2，在

12、作为锂离子电池的阳极材料被广泛研究，锰氧化物（MnOx）是一种很有前途的候选系列, 因为其相对于 Li/Li+相对较低的热力学平衡电压，和低电势，以及其环境友好、成本低。然而，仍有一些缺点如：（1）大的体积变化和充放电反应过程中金属颗粒逐渐集聚，（2）本质上低的电子电导率，这两者导致在循环过程中迅速衰败的能力，为克服这些挑战，许多研究都集中在碳纳米材料如把碳纳米管和碳纳米纤维加到MnOx中抑制粉化和容量衰减.After the discovery of gra-phene, much interest was paid to graphene/MnOx nano-composites for

13、LIBs with high capacity and long-life.23,2830 However, many of these composites were synthesized under severe conditions and usually needed higher cost for calcina-tion. For example, in Sun et al.s report, by mixing Mn(CH3-COO)2 and GO solutions, and adding hydrazine hydrate, a Mn-precursor/graphene

14、 intermediate was obtained, which was then annealed at 500 C in a 5% H2/Ar atmosphere for 5 h to obtain the nal MnO/graphene composite.31 A similar strategy was used for a N-doped MnO/graphene hybrid by calcining a precursor, i.e. Mn3O4/graphene, at 800 for 5 h under a NH3 atmosphere.32 In Qians gro

15、up, the precursors MnOOH nano-wires were rst synthesized through a hydrothermal procedureand a er the following calcination in air, Mn2O3 nanowires were obtained. The final MnOC coreshell nanowires were produced by exposing these Mn2O3 nanowires to argon and an acetylene/argon gas mixture at 500 .石墨

16、烯被发现后，更多的关注放在石墨烯/氧化锰纳米复合材料具有高容量、长寿命的锂离子电池上。然而，这些复合材料的合成需要在苛刻条件下，通常需要更高的成本。例如，在太阳等人的报告，通过混合Mn(CH3-COO)2和氧化石墨烯来解决，加入水合肼，Mn前驱体/石墨烯得到中间物，然后在5005% H2Ar气流中煅烧5小时得到复合材料，类似的方法被用于掺杂一氧化锰/石墨烯混合煅烧前驱体获得最终的一氧化锰/石墨烯复合材料，即Mn3O4 /石墨烯，在8005 h下氨气流中.在前组，前体MnOOH纳米线首先通过水热法合成了33和一个二以下在空气中煅烧，得到纳米三氧化二锰。最后的MnO C核壳纳米线的暴露这些Mn2O

17、3纳米线在500时在氩气和乙炔/氩气混合气体中产生.Dierent from many of the reported studies, we herein introduce MnO/rGO composites via a quite dierent synthesis approach. As reported in many publications,34,35 theoretical and experimental proof has proved that thermal reduction of graphene oxide would release CO and CO2,

18、and the COCO2 ratios were dependent on the thermal conditions. Therefore, in this work, we tried to utilize the reductive CO released from GO to in situ reduce MnO2 in the MnO2/GO composites to obtain MnO/rGO composites without using any external reductive gases, such as H2 and CO, which makes the s

19、ynthesis process with less cost and more safety. What is more important, GO is utilized as a solid reductant for the frist time and this valuable nding will arouse much interest in the GO research for material synthesis.不同于许多研究报道,我们这里介绍MnO / rGO复合材料通过一个完全不同的合成方法。在许多出版物报道,理论和实验证明热还原氧化石墨烯会释放CO和CO2.CO-

20、CO2的比率依赖于热条件。因此,在这项工作中,我们试图利用氧化石墨烯释放的还原CO去原地减少MnO2/GO 复合材料中的二氧化锰去获得MnO / rGO复合材料不使用任何外部还原气体,如H2和CO等,使合成工艺成本更低和更安全。更重要的是,去作为一个固体还原剂.这宝贵的首次发现会引起很大的兴趣去研究材料的合成In our previous research, it has been proven that the mild redox reaction between graphene oxide and KMnO4 would result in highly active d-MnO2 n

21、anosheets.36 In the present work, by adjusting the ratio of graphene oxide and KMnO4, dierent contents of graphene oxide can be retained in the d-MnO2/graphene oxide composites. As shown in Fig. 1, we typically tried three dierent weight ratios between KMnO4 and graphene oxide. The redox reaction be

22、tween the two reactants resulted in three precursors, P-MNP, P-MGC2 and P-MGC1. Through the further calcination under Ar at 500 C, d-MnO2 in the precursors (P-MGC2 and P-MGC1) can be reduced to MnO due to the reductive gas (CO) release from the thermolysis of graphene oxide, resulting in the formati

23、on of MGC2 and MGC1. No graphene oxide was found in the P-MNP, so that afer the calcination under Ar at 500 C, d-MnO2 was transferred to a-MnO2 nanoparticles (denoted as MNP). The general synthesis process for these manganese oxides and their hybrids with graphene is illustrated in Fig. 1 (see more

24、experimental details in the ESI).在我们之前的研究中,已经证明石墨烯之间的轻微的氧化还原反应和氧化KMnO4会导致d-MnO2 纳米片的高度活跃。在目前的工作,通过调整氧化石墨烯和高锰酸钾的比例,可以让不同含量的氧化石墨烯保留在d-MnO2 /氧化石墨烯复合材料。如图1所示,我们通常试着三种不同的重量比率的高锰酸钾和氧化石墨烯。两个反应物之间的氧化还原反应导致三个前前驱体,P-MNP,P-MGC2 P-MGC1。通过在500氩气中进一步煅烧 ,由于氧化石墨烯热解可以生成还原气体CO,所以d-MnO2的前体(P-MGC2和P-MGC1)可以还原为MnO.导致MGC

25、2和MGC1的形成。无氧化石墨烯在P-MNP中发现，所以，在500氩气中煅烧下，d-MnO2被转移到 - MnO2纳米粒子（记为MNP）。图1所示的是这些锰氧化物和石墨烯的合成及其杂交的一般过程（更多的实验细节请参阅ESI）View Article OnlinePaperResults and discussion结果与讨论The precursors resulting from the redox reaction between graphene oxide and KMnO4 were found to contain d-MnO2 with a monoclinic birnessi

26、te (containing K) phase from the XRD (Fig. SI1, ESI), similar to our reported results. And the TGA results in air (Fig. SI2ac, ESI) showed that no graphene oxide remained in P-MNP, while for P-MGC2 and P-MGC1, it can be implied that the remaining graphene oxide contents were about 14% and 37%, respe

27、ctively, by calculating the mass loss during heating in air. After annealing these precursors at 500 C for 90 min under an Ar atmosphere, dierent manganese oxides were obtained. Fig. 2 shows the XRD patterns of MGC1, MGC2 and MNP. It is obvious that MNP (Fig. 2c) is indexed to a pure -MnO2 phase wit

28、h a tetragonal crystal system (JCPDS no. 44-0141), while MGC2 (Fig. 2b) and MGC1 (Fig. 2a) readily correspond to a cubic phase of MnO (JCPDS no. 07-0230), and their TGA analysis in air indicates that rGO contents are about 18% and 39%, respectively (Fig. SI2df, ESI).与我们的报告结果相似，从氧化石墨烯和高锰酸钾氧化还原反应产生的前体

29、发现含有d-MnO2与水钠锰矿单斜晶系（含钾）从XRD相（图1，ESI）。用热量分析法分析空气（图si2aC，ESI）表明， 在P-MNP没有氧化石墨烯，而P-MGC2 和P-MGC1，可以暗含着氧化石墨烯的含量分别为约14%和37%，计算在空气中加热质量损失。这些前驱体退火后在500Ar气流下90分钟，获得了不同锰氧化物。图2显示了MGC1, MGC2 和 MNP的X射线衍射曲线。很明显，MNP（图2c）是由一个四方晶系的纯 - MnO2相，而MGC2（图2b）和MGC1（图2a）符合立方相的MnO，对它们在空气中进行热重量分析表明所含的氧化石墨烯分别约18%和39%，（图SI2dF，ESI

30、）。The high-resolution X-ray photoelectron spectroscopy (XPS) analysis is shown in Fig. 3a. The peaks at around 640 and 651 eV for MGC2 and MGC1 are attrib uted to Mn(II) 2p3/2 and 2p1/2, respectively,37 which are quite different from the peaks for MNP located at about 642 and 653 eV, the characteris

31、tics of Mn(IV).38 Raman spectra were obtained to further identify the structure and constituent of MNP, MGC2 and MGC1, as presented in Fig. 3b. The characteristic D band and G band of carbon materials are present in MGC2 and MGC1, but absent in MNP, further indicating that there is no graphene in MN

32、P. Addi-tionally, the peaks at around 580 and 650 cm 1 for MGC2 are assigned to manganese oxide.3941 In the sample MGC1, there is only one peak around 650 cm 1 for MnO, which may be due to the fact that the signal intensity for the metaloxygen bond is usually lower than that of the D and G bands for

33、 rGO. And in MGC1, the graphene content is higher than that in MGC2, so that the D and G peak intensities are even much higher than that for the metaloxygen bond. As a result, the peak at 580 cm 1 is not as obvious as that at 650 cm 1 in MGC1.高分辨率X射线光电子能谱（XPS）分析如图3a所示。在640和651 ev下MGC2 和 MGC1 的顶峰将属性造

34、成Mn（II）分别为2p3 / 2和2P1 / 2，这是完全不同于大约在642和653 eV MNP的顶峰峰位于Mn(IV)的特点，用拉曼光谱进一步识别得到MNP ,MGC2 和MGC1的结构和组成，如图3b给出。特征D带和G带碳材料，出现在MGC2 和MGC1，但没有在MNP，进一步表明在MNP没有石墨烯。在此基础上，峰值在580和650cm-1 MGC2被分配到氧化锰。样品中的MGC1，只存在一个峰值约650cm-1MnO，这可能是由于对金属氧键的信号强度通常低于该D和G带氧化石墨烯。在MGC1，石墨烯的含量高于MGC2，所以D和G的峰值强度甚至高于金属氧键。因此，在MGC1中580cm-

35、1的峰值不如在650cm-1的明显。Fig. 4, 5 and 6 show the typical SEM and TEM images of MNP, MGC2 and MGC1, respectively. Evidently, -MnO2 nano-particles in MNP are dispersed well with the size of about 50 nm with a narrow size distribution (Fig. 4a and c). For MGC2 and MGC1 as shown in Fig. 5 and 6, MnO nanoparti

36、cles are both with a size of ca. 50 nm, and it is also obvious to note that the graphene content in MGC2 is lower than that in MGC1, which leads to more aggregation of MnO in MGC2 while MnO nano-particles in MGC1 are dispersed well on the surface of rGO. The high-resolution TEM (HRTEM) images of MGC

37、2 (Fig. 5d) and MGC1 (Fig. 6d) show the interplanar distance of ca. 0.25 nm, corresponding to the (111) plane of cubic MnO. The FFT (Fast Fourier Transform) patterns in the inset in the HRTEM images also show the spot pattern representative of the crystalline phase, although the intensity is quite l

38、ow due to the low crys-tallinity of MnO nanoparticles. However, MNP showed a dierent lattice spacing of ca. 0.48 nm (Fig. 4d), which corre-sponds to the (200) plane of -MnO2. The N2 adsorption desorption isotherms (see Fig. SI3, ESI) also showed a higher BET specific surface area of MGC1 (46.3 m2 g

39、1) than that of MGC2 (27.4 m2 g 1)图4，5和6分别显示MNP，MGC2 和 MGC1的典型标准电子组件。显然，MNP中的 - MnO2纳米颗粒在分散粒度分布窄的大小约为50 nm（图4a和c）。对于MGC2和MGC1如图5和6所示，MnO纳米颗粒大小都约为50 nm，在MGC2中石墨烯的含量名显低于MGC1，导致MGC2中更多的MnO纳米颗粒聚集而MGC1中的MnO分散在氧化石墨烯表面。MGC2的高分辨透射电镜（HRTEM）图像（图5d）和MGC1的（图6d）显示面立方MnO的晶面间距约为0.25nm。FFT（快速傅里叶变换）在高分辨透射电子显微镜图像在嵌入模

40、式也表明结晶相的点模式的代表，虽然低结晶度的纳米MnO的强度很低。然而，MNP显示不同的晶格间距约0.48 nm（图4d），其对应的平面 - MnO2。N2吸附脱附等温线（见图SI3）也表现出MGC1（46.3 m2 g -1的BET特定表面积高于MGC2（27.4m2 g -1)The energy-dispersive spectra (EDS) also indicate the exis-tence of Mn, O and C in MGC1 and MGC2. The rough atom ratio of Mn to O is about 1 : 1 and the atom r

41、atios of C to Mn are also consistent with the previous analysis. For MNP, the rough atom ratio of Mn to O is about 1 : 2 and the little signal (about 1.5 atom%) for carbon may come from the environment or adsorbed CO2. From the above analysis, by increasing the initial ratio of graphene oxide to KMn

42、O4 in the redox reaction, the more graphene oxide can be remained in the resulting -MnO2/ GO composites (pure d-MnO2, i.e. P-MNP was obtained when the weight ratio of KMnO4 to GO was 4 : 1). During further heating treatment under an Ar atmosphere, the carbon in graphene skeleton cannot reduce MnO2 s

43、ince the temperature is only 500 C.42 The remaining graphene oxide undergoes thermolysis to release CO and CO2, as reported by many researchers.34,35 Thus, even in the inert atmosphere, MnO2 can be reduced to MnO, which is decorated on the graphene support and the remaining graphene oxide is also re

44、duced to rGO at the same time. This is quite different from results reported by Sun et al.,31 where Mn2+ was used as the Mn source and H2/Ar was used as the reductive gas for graphene oxide. For P-MNP, the absence of graphene oxide means the absence of CO release, so a-MnO2 nanoparticles were obtain

45、ed because of the phase change of d-MnO2 into a-MnO2 during high-temperature treatment. In summary, in this work, the reducing power of graphene oxide has been successfully proven and used to prepare MnO from MnO2 without any extra reductants.能量色散谱（EDS）也表明MGC1 和 MGC2中存在锰，氧和碳 。锰和氧的原子比率为11，碳和锰的原子比率还有待

46、分析，。MNP，Mn 和O粗略的原子比率约为1：2，小的误差（约1.5原子%）碳可能来自环境或吸附CO2。从以上的分析中，通过增加氧化石墨烯和高锰酸钾在氧化还原反应的初始比，氧化石墨烯更多的可以保持在产生的d-MnO2 /石墨复合材料（纯-mno2，当KMnO4和石墨烯的重量比为41可以得到P- MNP）。在进一步加热处理氩气下，,由于温度只有500，所以石墨烯的碳骨架不能减少MnO2,根据很多研究人员的报告，剩余的氧化石墨烯进行热解释放CO和CO2。因此，即使在惰性气体中，MnO2可以还原成MnO，装饰支持作用的石墨烯和剩余的石墨烯同时转化为氧化石墨烯。这和Sun等人报道结果有很大的不同，M

47、n2+作为锰源，氢气/氩气作为氧化石墨烯的还原气体。对于P-MNP，氧化石墨烯的缺乏意味着CO释放的情况下，由于相变为高温处理-MnO2， - MnO2得到 - MnO2纳米颗粒。总之，在这项工作中，总之,在这个工作中,氧化石墨烯的还原能力已经成功地证明,用于准备MnO没有用任何额外的还原剂。 The electrochemical lithium-storage performance of the as-prepared MnO/rGO composites was also investigated. The galvanostatic discharge/charge cycling

48、performance was tested at a current of 100 mA g 1 with a voltage window of 0.053.5 V. As shown in Fig. 7a, for a current density of 100 mA g 1, the first discharge capacity of MGC1 was over 1800 mA h g 1, and the initial capacity loss is about 50%, which is believed due to the disordered rGO and the

49、 trap sites for Li on its surface to form SEI. Interestingly, in the following cycling, the capacity increased gradually and stabilized at 900 mA h g-1 after 85 cycles. The capacity rise has been reported in many published studies and was considered to be attributed to a possible activation process

50、in the electrode.31,33 The initial capacity has a significant irreversible component; however, capacity in subsequent cycles is of similar order to that expected for Mn2+/ Mn0 conversion. On a number of cycles, the capacity exceeded than that expected for just the Mn couple and may possibly reflect

51、a component due to the organic polymeric/gel like films formed reversibly by decomposition at low potential., According to the theoretical overall reaction between lithium and graphene nanosheets, 2C + Li+ + e- LiC2 (with a capacity of 1116 mA h g 1)4446 and the theoretical conversion of MnO and Li,

52、 MnO + 2Li+ + 2e-Li2O + Mn (with a capacity of 756 mA h g 1),47 as well as the content analysis of the composite through TGA shown in Fig. SI2df, the theoretical capacity for MGC1 is about 896 mA h g 1, which is in good agreement with the stable capacity of 900 mA h g 1 after 85 cycles at a low curr

53、ent density of 100 mA g -1.对所制备的二氧化锰/石墨烯复合物的电化学储锂性能进行了研究。在电流100mAg-1与电压0.053.5 V下，测试恒电流充/放电的循环性能，在电流密度为100mAg-1，MGC1首次放电容量超过1800 mA h g -1，初始容量损失约50%，这被认为是由于无序的氧化石墨烯和陷阱的网站里在其表面形成SEI。有趣的是，在以下循环中，在循环85次后，容量逐渐增加并稳定在900mA h g -1。在许多已发表的研究报告中认为，能力的上升，可能是由于电极中的一个激活过程。初始容量有显著的不可逆的成分；然而，在随后的循环中，预计Mn2+ / Mn0

54、转换是类似的命令。在一个周期数，容量超过了预期只是Mn结合和可能反映组件，由于有机高分子/凝胶薄膜在低电位可以被分解， 根据锂和石墨烯之间的理论总反应，2C + Li+ + e- LiC2（容量为1116mAg-1）,以及MnO和Li的理论转换，MnO + 2Li+ + 2e-Li2O + Mn （容量为756 mA h g-1）、通过热重量分析法对复合材料的内容进行分析，MGC1的理论容量是896mAhg-1，这与900 mA h g-1在100 mAg-1低电流密度下循环85次 后的稳定容量一致。View Article OnlinePaper In the following rate

55、capability test at various current densities, discharge capacities of 750 mA h g -1, 580 mA h g 1, 400 mA h g 1 and 160 mA h g 1 were retained at current densities of 200 mA g 1, 400 mA g -1, 800 mA g 1 and 1.6 A g 1, respectively. It seems that the rate performance is not as high as that of other r

56、eported carbonMnO materials.31,33 For the MnO/ graphene prepared by Sun et al., the reversible capacity is high up to 2014.1 mA h g 1 at a current of 200 mA g 1 and 625.8 mA h g 1 at a current of 3000 mA g 1.31 Also according to Li et al., the MnOC electrode delivered a capacity of 861 mA h g 1 at a

57、 current of 100 mA g 1 and 462 mA h g 1 at a current of 2000 mA g 1.33 The relatively low rate capability may be ascribed to the relatively low electronic conductivity of reduced graphene oxide in the active material that results in the incomplete discharge/ charge process at high current densities.

58、 However, importantly, the capacity was able to recover to more than 900 mA h g -1 after 120 cycles when the current density was returned to 100 mA g 1. More details of the discharge/charge process can be seen from the discharge/charge voltage profile in Fig. 7b, which shows a discharge plateau at ca. 0.31 V in the 1st cycling and a shifted plateau at ca. 0.42 V in the later cycling. It also shows a chargin