Subscriber access provided by Gothenburg University Library
Article
Laser Reduction of Nitrogen-rich Carbon Nanoparticles@Graphene Oxide Composites for High Rate Performance Supercapacitors Xiu-Yan Fu, Dong-Lin Chen, Yan Liu, Hao-Bo Jiang, Hong Xia, Hong Ding, and Yong-Lai Zhang ACS Appl. Nano Mater., Just Accepted Manuscript • DOI: 10.1021/acsanm.7b00225 • Publication Date (Web): 09 Jan 2018 Downloaded from http://pubs.acs.org on January 10, 2018
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
ACS Applied Nano Materials is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Applied Nano Materials
Laser Reduction of Nitrogen-rich Carbon Nanoparticles@Graphene Oxides Composites for High Rate Performance Supercapacitors Xiu-Yan Fu,a Dong-Lin Chen,a Yan Liu,b Hao-Bo Jiang,b Hong Xia,a Hong Ding,c and Yong-Lai Zhanga* a. State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China. b. Key Laboratory of Bionic Engineering (Ministry of Education), Jilin University, Changchun 130022, China. c. State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun130012, China. KEYWORDS: direct laser reduction, egg albumen, nitrogen-rich carbon nanoparticles, solidstate doping agent, graphene oxides composites, supercapacitors
ACS Paragon Plus Environment
1
ACS Applied Nano Materials 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 2 of 26
ABSTRACT Nitrogen doped graphene or graphene derivatives have been proven superior electrode materials for high performance supercapacitors. Synchronous N doping and reduction of graphene oxides (GO) is an effective approach to prepare such electrode materials. However, current strategies are limited to the use of liquid or vapor doping agents, making the preparation process complex and less environmentally friendly. We here report a facile way to prepare nitrogen-rich carbon nanoparticles (NCNPs), which can be employed as a solid-state doping agent for efficient N-doping of GO through direct laser writing photoreduction. The doping degree has been tuned by varying the mass ratios of the NCNPs in the composites. After laser treatment, the composites show N concentration as high as 7.78 at%. Using the N doped graphene composites as electrodes, the as-fabricated supercapacitors show high rate performance and obvious enhanced capacitance, revealing great potential for energy storage and conversion devices.
INTRODUCTION In recent years, enormous research interests have been paid to the development of effective and sustainable energy supply systems which require not only high energy density but high power density. Thus, high-quality energy storage systems become more and more important. As is well known, batteries1 and supercapacitors are two kinds of typical energy storage devices. The former always have higher energy density but lower power density; whereas the latter exhibit higher power density but suffer from much lower energy density. Such limitation more or less restricts their applications as independent energy storage devices.2-3 To fully utilize the superior properties of supercapacitors, such as high rate capabilities and long cycle lives which
ACS Paragon Plus Environment
2
Page 3 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Applied Nano Materials
benefit from their electrical double layers (EDLs) ions storage mechanism, issues with respect to insufficient capacitance have to be solved first. In this regard, developing efficient electrode materials is of critical importance. Many strategies have been performed to enhance the device performance, such as designing layered porous structure, 4-5 especially by choosing suitable precursors. Nowadays, graphene and its derivatives emerge as appealing electrode materials for highperformance supercapacitors, since graphene that possesses excellent electrical conductivity, flexibility, mechanical strength and high surface area (over 2600m2g-1) is an ideal electrode material.6 However, at present, it’s still a big challenge to realize mass production of graphene through a cost effective manner, although a number of studies have proven the preparation of graphene at lab conditions, including mechanical exfoliation of graphite,7-8 solvent exfoliation of graphite 9-10 and chemical vapor deposition (CVD) growth on metal substrates (e.g., Cu, Ni).11-14 As an alternative, GO prepared by simple chemical oxidation of graphite have been considered a potential precursor for mass production of graphene-related materials.15-16 Yet, due to the chemical oxidation treatments, GO has a lot of oxygen-containing groups (OCGs), and thus it is insulating, which make it unsuitable for applications as electrodes. Nevertheless, it is possible to remove the OCGs on GO sheets and recover the conductivity by using suitable reduction treatments. Generally, GO could be effectively reduced by chemical reduction, thermal annealing and photoreduction, or a combination of the two methods, among which the photoreduction strategies have been considered a promising route to prepare graphene-related materials since photoinduced deoxygenizations of GO not only permits effective removal of OCGs, but also enables the formation of highly porous structures, revealing great potential for the development of
ACS Paragon Plus Environment
3
ACS Applied Nano Materials 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 4 of 26
electrode materials. As typical examples, Gao at al. reported direct laser writing of microsupercapacitors on hydrated GO films, and the resulting devices showed good cycling stability and energy storage capability;17 EI-Kady et al. reported the flexible graphene-based electrochemical capacitors by laser scribing technology.18 To further improve the capacitance of such reduced graphene oxide (RGO)-based supercapacitors, doping with heteroatoms has been proven to be a simple but useful approach,19-24 since the presence of heteroatoms may introduce additional heteroatomic defects and functional groups, which can alter the electronic structure and electrochemical properties, leading to better conductivity, stability, chemical reactivity and sheet-to-sheet separation compared to pristine materials. Among of the numerous doping methods, doping with nitrogen seems a preferred choice for its comparable atomic size and five valence electrons available to form strong valence bonds with carbon atoms. It has been reported that the specific capacity of graphene can be increased four times after nitrogen doping.25 Despite the fact that heteroatom doping could be easily realized through traditional chemical/thermal approaches, for instance hydrothermal/solvothermal treatments and hightemperature anneal, the doping source is generally limited to liquid and gas phase chemicals, which is not suitable for photoreduction treatments. In our previous work, we have reported a femtosecond laser induced photoreduction and simultaneous N doping of GO in ammonia atmosphere.26 Despite ~10% doping concentration of nitrogen was achieved, the doping efficiency is quite low and self-made ammonia chamber was very complex. To facilitate the heteroatom doping during photoreduction treatments, solid doping agents are highly desired. However, considering the problems with respect to the homogeneous distribution of doping agents, the dissociation of heteroatoms and the influences of the solid residuals, relative works are still rare.
ACS Paragon Plus Environment
4
Page 5 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Applied Nano Materials
In this study, we demonstrated the preparation of NCNPs as a solid-state doping agent for efficient N-doping of GO in the process of direct laser writing photoreduction. By simply hydrothermal treatment of egg albumen, NCNPs with N concentration of 8.03% and a size distribution of 14-21 nm have been successfully prepared. Since both the NCNPs and GO could be well dispersed in water, a composite with tunable contents of the two materials could be easily obtained. Then the composites were dried in air at ambient condition and a solid film formed. Direct laser reduction of the NCNPs and GO (NCNPs@GO) composite leads to the formation of a porous composites. NCNPs serve as solid doping agent for nitrogen source, and the same time, they prevent the stacking of graphene layer during laser reduction. N content of the resultant R-NCNPs@GO composites can reach ~7.78 at%. Finally, we have also demonstrated that supercapacitors using the R-NCNPs@GO composites as electrodes showed much higher rate performance and relatively better specific capacitance value as compared with that of bare RGO-based supercapacitors (4.27 mF/cm2) prepared in the same way. After 1000 cycles, the specific capacitance retention was at least 95.45%, which indicates that the supercapacitors based on R-NCNPs@GO composites showed significantly improved capacitance and without sacrificing their cycle stability. EXPERIMENTAL METHODS Preparation of GO: GO was prepared from purified natural graphite (Aldrich,
