Vertically Aligned Carbon Nanotubes Grown on Graphene Paper as Electrodes in Lithium‐Ion Batteries and Dye‐Sensitized Solar Cells

Abstract

Vertically aligned carbon nanotubes (VACNTs) possess the advantages of a high degree of order, good controllability, and easy manipulation. Thus, their synthesis, properties, and potential for applications have been intensively investigated. [1][2][3][4][5] VACNTs are usually grown by chemical vapor deposition (CVD) on substrates with pre-deposited catalysts. Due to the rigorous CVD synthesis conditions, substrates employed for VACNT growth should be thermally and chemically stable materials, such as SiO 2 /Si, Al 2 O 3 , or quartz. A problem thus arising is that these substrates are usually insulators, which hampers the direct application of VACNTs in those areas that require desirable integrated electrical and thermal conductivities. [ 6 ] For example, a mismatching problem often emerges when assembling devices based on VACNTs due to the rigidity and poor conductivity of the substrates. To solve this problem, some researchers have developed multiform but complicated methods to transfer VACNTs from the insulating substrates to conducting substrates by post-synthesis processing, which facilitates the application of VACNTs in some electronic devices, such as fi eld emitters. [ 7,8 ] On the other hand, Tatsuki et al. reported direct growth of VACNTs on Ni-based alloy foils. [ 9 ] Although excellent fi eld emission homogeneity was demonstrated, the 30 nm thick alumina buffer layer deposited between the metal substrate and catalyst fi lm weakens the electrical contact and mechanical adhesion between the VACNTs and the metal substrate. The incompatible thermal expansion coeffi cients of alumina and metal may also lead to detaching of the VACNTs and the alumina buffer layer from the metal substrate.Graphene is a newly discovered 2D carbon material with excellent conductivity, mechanical properties, [ 10,11 ] and more importantly, compatibility with CNTs. Therefore, graphene can be an ideal substrate for VACNT growth. Recently, Lee et al. demonstrated the growth of VACNTs on a ∼ 7 nm thick reduced graphene fi lm supported by silicon wafer. The VACNT/ graphene hybrid fi lm infi ltrated with a poly(dimethyl siloxane) (PDMS) elastomer displayed good mechanical properties, electrical conductivity, and fi eld emission performance. [ 12 ] Nitrogendoped VACNTs grown on mechanically compliant graphene fi lm for a fl exible fi eld emitter were also demonstrated by Lee et al. [ 13 ] Jeong et al. reported a flexible room temperature NO 2 gas sensor consisting of a VACNT/reduced graphene hybrid film supported by a polyimide substrate. [ 14 ] Paul et al. prepared a 3D pillared graphene nanostructure comprising graphene and aligned carbon nanotubes by a one-step CVD method. [ 15 ] Zhang et al. demonstrated desirable visible light photocatalytic performance for a 3D pillared CNT/reduced graphene oxide composite material. [ 16 ] Fan et al. prepared a 3D CNT/graphene sandwich with short CNT pillars ( ∼ 100 nm in length) grown between graphene layers or by ultrasonicating purifi ed, shortcut CNTs in a graphene oxide suspension followed b...

Critical Insight into the Relentless Progression Toward Graphene and Graphene‐Containing Materials for Lithium‐Ion Battery Anodes

“…[ 60 ] Despite previous papers claimed a certain fragility of bare RGO paper electrodes, [ 35 ] these last two research efforts clearly demonstrated that the introduction of defects, or the direct functionalization of RGO's surface with other electroactive species, could enable fl exible graphene-based electrodes. Similarly, other research efforts on N-doped RGO [ 61 ] and RGO paper functionalized with CNT [ 62,63 ] were reported, but no substantial improvement in terms of electrochemical performance could be observed (Table 1 ). Moreover, a chemically activated RGO paper was also tested as LIB anode [ 64 ] but, unfortunately, it showed very poor performance (i.e., 1 st cycle irreversible capacity of about 86% and a lithiation capacity retention of about 16% after 10 cycles at 20 mA g −1 ) ( Table 1 ).…”

High lithium anodic performance of highly nitrogen-doped porous carbon prepared from a metal-organic framework

“…13), graphene (approximately 568 mA h g À 1 ) (ref. 14) and carbon nanotube and graphene composites 15,16 . In addition, partially graphitized porous carbon is a class of emerging materials with promising chemical properties for LIBs due to their relatively low cost, high conductivity and porous structure, which make them very attractive materials.…”

Carbon-Based Metal-Free Electrocatalysis for Energy Conversion, Energy Storage, and Environmental Protection

“…[197], Copyright 2017, Nature Group aligned SWCNT array also displayed a high conversion efficiency of 5.5%, comparable to 5.6% obtained with a Pt-based DSSC tested under the same conditions [195]. In addition, carbon catalysts comprised of CNTs coated onto a flexible graphene paper achieved 83% conversion efficiency of that of a Pt electrode [196].…”