Sustainable catalytic graphitization of biomass to graphitic porous carbon by constructing permeation network with organic ligands

Common strategies for catalytic graphitization of biochar into graphitic porous carbon(GPC)still face great challenges,such as the realization of simple procedures,energy conservation,and green processes.Controlling over the graphitization degree and pore structure of biochar is the key to its structural diversification.Herein,a clean and energy-efficient method is developed to synthesize adjustable graphitic degree and structure porosity GPC from rice husk-based carbon(RHC)at a relatively low temperature of 800–1000°C with environment-benign organometallic catalyst ethylenediaminetetraacetic acid ferric sodium salt(EDTA-iron)and the recovery ratio of catalyst is as high as 97%.The formed by the organic ligands of EDTA-iron facilitates the etching of RHC surface and pore by iron,resulting in highly graphitized and developed porous GPCs.The pore structure and graphitization degree of GPCs can be adjusted by altering the catalyst loading,temperature,and holding time.The catalyst EDTA-iron with a lower concentration mainly plays the role of etching,which promotes the formation of porous carbon with larger surface area(SBET=1187.2 m^(2)·g^(-1)).The catalyst with higher concentration mainly plays the role of catalyzing graphitization and promotes the obtaining of graphitic carbon with high graphitization degree(ID/IG=0.19).The mechanism of EDTA-iron catalyzed graphitization of RHC is explored by the comprehensive analysis of BET,XRD,Raman,TEM and TGA.This research not only provides an efficient method for the preparation of high-quality biomass-based graphite carbon,but also provides a feasible method for the preparation of biomass-based porous carbon.

Effect of praseodymium on catalytic graphitization of furan resin carbon

We introduced a new catalyst,rare earth element praseodymium,for the catalytic graphitization of furan resin carbon.The extent of graphitization of the furan resin carbon was examined by X-ray diffraction and Raman spectroscopy.The morphology of furan resin carbon was characterized by scanning electron microscopy.The effects of the praseodymium content and the heat-treatment temperature on the catalytic graphitization of furan resin carbon were also investigated.The results indicated that the praseodymium c...

Catalytic graphitization of Mo-B-doped polyacrylonitrile(PAN)-based carbon fibers

A novel carbon fiber pretreatment was proposed.Polyacrylonitrile(PAN)-based carbon fibers were first anodized in H3PO4 electrolyte to achieve an active surface,and then coated with Mo-B catalysts by immersed the carbon fibers in a uniformly dispersed Mo-B sol.The as-treated carbon fibers were then graphitized at 2 400 ℃ for 2 h.The structural changes were characterized by X-ray diffractometry(XRD),Raman spectroscopy,scanning electron microscopy(SEM) and high-resolution transmission electronic microscopy(HRTEM).The results show that much better graphitization can be achieved in the presence of Mo-B,with an interlayer spacing(d002) of 0.335 8 nm and a crystalline size(Lc) of 28 nm.

Catalytic graphitization of polyacrylonitrile(PAN)-based carbon fibers with Fe-Cr_2O_3 composite coating

The process of electrodepositing Fe-Cr2O3 composite coating on polyacrylonitrile （PAN）-based carbon fibers and its catalytic graphitization were studied. Carbon fibers with and without electrodeposited Fe-Cr2O3 composite coating were heat treated at different temperatures and the structural changes were characterized by XRD, Raman spectroscopy and SEM. The results indicate that Fe-Cr2O3 composite coating exhibits a significant catalytic effect on graphitization of carbon fibers at low temperatures. When the Fe-Cr2O3-coated carbon fibers were heat treated at 1 300℃ the interlayer spacing （doo2） and ratio of relative peak area （AD/AG） reach 3.364/k and 0.34, respectively. Whereas, the extent of graphitization of pristine carbon fibers is comparatively low even after heat treatment at 2 800℃ and the values of doo2 and AD/AG are 3.414 A and 0.68, respectively. The extent of graphitization of carbon fibers increases not only with the increase of the catalyst gross but also the Cr2O3 content in Fe-Cr2O3 coating. The catalytic effect of Fe-Cr2O3 composite coating accords with the dissolution-precipitation mechanism.

Catalytic graphitization of carbon/carbon composites by lanthanum oxide

Graphitized carbon/carbon composites were prepared by the process of catalytic graphitization with the rare-earth catalyst, lantha-num oxide （La2O3）, in order to increase the degree of graphitization and reduce the electrical resistivity. The modified coal tar pitch and coal-based needle coke were used as carbon source, and a small amount of La2O3 was added to catalyze the graphitization of the disordered carbon materials. The effects of La2O3 catalyst on the graphitization degree and microstructure of the carbon/carbon composites were investi-gated by X-ray diffraction, scanning electron microscopy, and Raman spectroscopy. The results showed that La2O3 promoted the formation of more perfect and larger crystallites, and improved the electrical/mechanical properties of carbon/carbon composites. Carbon/carbon compos-ites with a lower electrical resistivity （7.0 ？？？m） could be prepared when adding 5 wt.% La2O3 powder with heating treatment at 2800 oC. The catalytic effect of La2O3 for the graphitization of carbon/carbon composites was analyzed.

Highly electrically conductive graphene papers via catalytic graphitization

The highly electrically conductive graphene papers prepared from graphene oxide have shown promising perspectives in flexible electronics,electromagnetic interference(EMI)shielding,and electrodes.To achieve high electrical conductivity,the graphene oxide precursor usually needs to be graphitized at extremely high temperature(~2,800°C),which severely increases the energy consumption and production costs.Here,we report an efficient catalytic graphitization approach to fabricate highly conductive graphene papers at lower annealing temperature.The graphene papers with boron catalyst annealed at 2,000°C show a high conductivity of~3,400 S·cm^(-1),about 47%higher than pure graphene papers.Boron catalyst facilitates the recovery of structural defects and improves the degree of graphitization by 80%.We further study the catalytic effect of boron on the graphitization behavior of graphene oxide.The results show that the activation energy of the catalytic graphitization process is as low as 80.1 kJ·mol^(–1)in the temperature ranges studied.This effective strategy of catalytic graphitization should also be helpful in the fabrication of other kinds of highly conductive graphene macroscopic materials.

High-performance porous carbon foams via catalytic pyrolysis of modified isocyanate-based polyimide foams for electromagnetic shielding

Porous carbon skeletons(PCSs)derived from isocyanate-based aromatic polyimide foams(PIFs)by high-temperature pyrolysis are very promising in the fabrication of high-performance polymer composite foams for electromagnetic interference(EMI)shielding due to their efficient conductive networks and facile preparation process.However,severe volumetric shrinkage and low graphitization degree is not conducive to enhancing the shielding efficiency of the PCSs.Herein,ferric acetylacetonate and carbon-nanotube coating have been introduced in isocyanate-based PIFs to greatly suppress the serious shrinkage during pyrolysis and improve the graphitization degree of the final carbon foams through the Fe-catalytic graphitization process,thereby endowing them with better EMI-shielding performance even at lower pyrolysis temperature compared to the control samples.Moreover,compressible polydimethylsiloxane(PDMS)composite foams with the as-prepared carbon foams as prefabricated PCSs have also been fabricated,which could provide not only stable shielding effectiveness(SE)performance even after a thousand compressions,but also multiple functions of Joule heating,thermal insulation and infrared stealth.This study offers a feasible route to prepare high-performance PCSs in a more energy-efficient manner via PIF pyrolysis,which is very promising in the manufacture of multifunctional conductive polymer composite foams.

Ultrathin porous graphitic carbon nanosheets activated by alkali metal salts for high power density lithium-ion capacitors

Graphitic carbons with reasonable pore volume and appropriate graphitization degree can provide efficient Li+/electrolyte-transfer channels and ameliorate the sluggish dynamic behavior of battery-type carbon negative electrode in lithium-ion capacitors(LICs).In this work,onion-like graphitic carbon materials are obtained by using carbon quantum dots as precursors after sintering,and the effects of alkali metal salts on the structure,morphology and performance of the samples are focused.The results show that alkali metal salts as activator can etch graphitic carbons,and the specific surface area and pore size distribution are intimately related to the description of the alkali metal salt.Moreover,it also affects the graphitization degree of the materials.The porous graphitic carbons(SGCs)obtained by NaCl activation exhibit high specific surface area(77.14 m^(2)·g^(-1))and appropriate graphitization degree.It is expectable that the electrochemical performance for lithium-ions storage can be largely promoted by the smart combination of catalytic graphitization and pores-creating strategy.High-performance LICs(S-GCs//AC LICs)are achieved with high energy density of 92 Wh·kg^(-1)and superior rate capability(66.3 Wh·kg^(-1)at10 A·g^(-1))together with the power density as high as10020.2 W·kg^(-1).

Graphitic nanorings for super-long lifespan lithium-ion capacitors

Porous graphitic carbon nanorings(PGCNs)are proposed by smart catalytic graphitization of nano-sized graphene quantum dots(GQDs).The as-prepared PGCNs show unique ring-like morphology with diameter around 10 nm,and demonstrate extraordinary mesoporous structure,controllable graphitization degree and highly defective nature.The mechanism from GQDs to PGCNs is proven to be a dissolution-precipitation process,undergoing the procedure of amorphous carbon,intermediate phase,graphitic carbon nanorings and graphitic carbon nanosheets.Further,the relationship between particles size of GQDs precursor and graphitization degree of PGCNs products is revealed.The unique microstructure implies PGCNs a broad prospect for energy storage application.When applied as negative electrode materials in dual-carbon lithium-ion capacitors,high energy density(77.6 Wh·kg^(−1))and super long lifespan(89.5%retention after 40,000 cycles at 5.0 A·g^(−1))are obtained.The energy density still maintains at 24.5 Wh·kg^(−1)even at the power density of 14.1 kW·kg^(−1),demonstrating excellent rate capability.The distinct microstructure of PGCNs together with the strategy for catalytic conversion from nanocarbon precursors to carbon nanorings opens a new window for carbon materials in electrochemical energy storage.