The preparation of a synthetic pitch from aromatic monomers could easily regulate structure orientation at the molecu-lar level,which would be useful in fabrication.An isotropic synthetic pitch was prepared by a chlor...The preparation of a synthetic pitch from aromatic monomers could easily regulate structure orientation at the molecu-lar level,which would be useful in fabrication.An isotropic synthetic pitch was prepared by a chlorine-and/or nitrogen-induced sub-stitution polymerization reaction method using aromatic hydrocarbon precursors containing Cl and N,which for this study were chloromethyl naphthalene and quinoline.This method was verified by investigating the structural changes under different synthesis conditions,and the synthesis mechanism induced by aromatics containing Cl was also probed.The result shows that the pyridinic N in quinoline contains a lone pair of electrons,and is an effective active site to induce the polymerization reaction by coupling with aromatic hydrocarbons containing Cl.The reaction between such free radicals causes strong homopolymerization and oligomeriza-tion.A higher reaction temperature and longer reaction time significantly increased the degree of polymerization and thus increased the softening point of the pitch.A linear molecular structure was formed by the Cl substitution reaction,which produced a highly spinnable pitch with a softening point of 258.6℃,and carbon fibers with a tensile strength of 1163.82 MPa were obtained.This study provides a relatively simple and safe method for the preparation of high-quality spinnable pitch.展开更多
Lignin-derived porous carbons have emerged as promising electrode materials for supercapacitors.However,the challenge remains in designing and controlling their structure to achieve ideal electrochemical performance d...Lignin-derived porous carbons have emerged as promising electrode materials for supercapacitors.However,the challenge remains in designing and controlling their structure to achieve ideal electrochemical performance due to the complex molecular structure of lignin and its intricate chemical reactions during the activation process.In this study,three porous carbons were synthesized from lignin by spray drying and chemical activation with vary-ing KOH ratios.The specific surface area and structural order of the prepared porous carbon continued to increase with the increase of the KOH ratio.Thermogravimetric-mass spectrometry(TG-MS)was employed to track the molecular fragments generated during the pyrolysis of KOH-activated lignin,and the mechanism of the thermochemical conversion was investigated.During the thermochemical conversion of lignin,KOH facili-tated the removal of H2 and CO,leading to the formation of not only more micropores and mesopores,but also more ordered carbon structures.The pore structure exhibited a greater impact than the carbon structure on the electrochemical performance of porous carbon.The optimized porous carbon exhibited a capacitance of 256 F g-1 at a current density of 0.2 A g-1,making it an ideal electrode material for high-performance supercapacitors.展开更多
The chemical activation of various precursors is effective for creating additional closed pores in hard carbons for sodium storage.However,the formation mechanism of closed pores under the influence of pore-forming ag...The chemical activation of various precursors is effective for creating additional closed pores in hard carbons for sodium storage.However,the formation mechanism of closed pores under the influence of pore-forming agents is not well understood.Herein,an effective chemical activation followed by a high-temperature self-healing strategy is employed to generate interconnected closed pores in lignin-derived hard carbon(HCs).By systematic experimental design combined with electron paramagnetic res-onance spectroscopy,it can be found that the content of free radicals in the carbon matrix influences the closure of open pores at high temperatures.Excessively high activation temperature(>700 C)leads to a low free radical concentration,making it difficult to achieve self-healing of open pores at high tempera-tures.By activation at 700°C,a balance between pore making and self-healing is achieved in the final hard carbon.A large number of free radicals triggers rapid growth and aggregation of carbon microcrys-tals,blocking pre-formed open micropores and creating additional interconnected closed pores in as-obtained hard carbons.As a result,the optimized carbon anode(LK-700-1300)delivers a high reversible capacity of 330.8 mA h g^(-1) at 0.03 A g^(-1),which is an increase of 86 mA h g^(-1) compared to the pristine lignin-derived carbon anode(L-700-1300),and exhibits a good rate performance(202.1 mA h g^(-1) at 1 A g^(-1)).This work provides a universal and effective guidance for tuning closed pores of hard carbons from otherprecursors.展开更多
Sustainable energy conversion and storage technologies are a vital prerequisite for neutral future carbon.To this end,carbon materials with attractive features,such as tunable pore architecture,good electrical conduct...Sustainable energy conversion and storage technologies are a vital prerequisite for neutral future carbon.To this end,carbon materials with attractive features,such as tunable pore architecture,good electrical conductivity,outstanding physicochemical stability,abundant resource,and low cost,have used as promising electrode materials for energy conversion and storage.Defect engineering could modulate the structures of carbon materials,thereby affecting their electronic properties.The presence of defects on carbons may lead to asymmetric charge distribution,change in geometrical configuration,and distortion of the electronic structure that may result in unexpected electrochemical performances.In this review,recent advances in defects of carbons used for energy conversion and storage were examined in terms of types,regulation strategies,and fine characterization means of defects.The applications of such carbons in supercapacitors,rechargeable batteries,and electrocatalysis were also discussed.The perspectives toward the development of defect engineering carbons were proposed.In all,novel insights related to improvement in high-performance carbon materials for future energy conversion and storage applications were provided.展开更多
In-situ MgO-doped ordered mesoporous carbon(OMC@MgO)was fabricated by formaldehyde-free self-assembly method,in which biomass-derived tannin was used as carbon precursor replacing fossil-based phenolics,Mg^(2+)as both...In-situ MgO-doped ordered mesoporous carbon(OMC@MgO)was fabricated by formaldehyde-free self-assembly method,in which biomass-derived tannin was used as carbon precursor replacing fossil-based phenolics,Mg^(2+)as both cross-linker and precursor of catalytic sites.Up to~20 wt% MgO could be doped in the carbon skeleton with good dispersion retaining well-ordered mesoporous structures,while more MgO content(35 wt%)led to the failing in the formation of ordered mesoporous structure.The OMC@MgO possessed a high specific surface area(298.8 m^(2) g^(-1)),uniform pore size distribution(4.8 nm)and small crystallite size of MgO(1.73 nm)due to the confinement effect of ordered mesoporous structure.Using OMC@MgO as the heterogeneous catalyst,a maximum fructose yield of 32.4% with a selectivity up to 81.1%was achieved from glucose in water(90℃,60 min),which is much higher than that obtained using the MgO doped active carbon via conventional post-impregnation method(26.5%yield with 58.3% selectivity).Higher reaction temperature(>90℃)resulted in decrease of selectivity due to the formation of humins.The designed OMC@MgO displayed tolerant to high initial glucose concentrations(10 wt%)and could remain good recyclability without significant loss of activity for three cycles.展开更多
We employed the previously developed micro porous activated carbon models of different pore sizes ranges of 9-11?,10-12?,and 13-16?that were constructed by molecular simulation method based on a random packing of plat...We employed the previously developed micro porous activated carbon models of different pore sizes ranges of 9-11?,10-12?,and 13-16?that were constructed by molecular simulation method based on a random packing of platelets of carbon sheets,functionalized with oxygen containing groups,to study the adsorption behavior of methane molecules.In studying methane adsorption behavior,we used Grand Canonical Monte Carlo and Molecular Dynamics methods at different temperatures of 273.15,298.15 and303.15 K.Adsorption isotherms,isosteric heats of adsorption,adsorption energy distributions and porosity changes of the models during adsorption process were analyzed and discussed.Furthermore,radial distribution Functions,relative distribution and diffusion coefficients of methane molecules in activated carbon models at different temperatures were studied.After the analysis,the main results indicated that large micro pores activated carbons were favorable for storing methane at lower temperatures and small micro pores were the most favorable for adsorbing methane molecules at higher temperatures.Interestingly,the developed model structures showed high capacities to store methane molecule at ambient temperatures and low pressure.展开更多
Suzuki-Miyaura reaction of aryl halides with phenylboronic acid using a heterogeneous palladium catalyst based on activated carbons(AC) was systematically investigated in this work. Two different reaction modes(batch ...Suzuki-Miyaura reaction of aryl halides with phenylboronic acid using a heterogeneous palladium catalyst based on activated carbons(AC) was systematically investigated in this work. Two different reaction modes(batch procedure and continuous-flow procedure) were used to study the variations of reaction processing. The heterogeneous catalysts presented excellent reactivity and recyclability for iodobenzene and bromobenzene substrates in batch mode, which can be attributed to stabilization of Pd nanoparticles by the thiol and amino groups on the AC supports. However, significant dehalogenation in the reaction mixture and Pd leaching from the heterogeneous catalysts were observed in continuous-flow mode.This unique phenomenon in continuous-flow mode resulted in a dramatic decline in reaction selectivity and durability of heterogeneous catalysts comparing with that of batch mode. In addition, the heterogeneous Pd catalysts with thiol-and amino-modified AC supports exhibited different reactivity and durability in batch and continuous-flow mode owing to the difference of interaction between Pd species and AC supports.展开更多
Catalytic hydrogenation of CO_(2) using renewable hydrogen not only reduces greenhouse gas emissions,but also provides industrial chemicals.Herein,a Co-Fe bimetallic catalyst was developed by a facile reactive ball-mi...Catalytic hydrogenation of CO_(2) using renewable hydrogen not only reduces greenhouse gas emissions,but also provides industrial chemicals.Herein,a Co-Fe bimetallic catalyst was developed by a facile reactive ball-milling method for highly active and selective hydrogenation of CO_(2) to value-added hydrocarbons.When reacted at 320℃,1.0 MPa and 9600 mL h^(-1) g_(cat)^(-1),the selectivity to light olefin(C_(2)^(=)-C_(4)^(=)) and C_(5)+ species achieves 57.3% and 22.3%,respectively,at a CO_(2) co nversion of 31.4%,which is superior to previous Fe-based catalysts.The CO_(2) activation can be promoted by the CoFe phase formed by reactive ball milling of the Fe-Co_(3)O_(4) mixture,and the in-situ Co_(2)C and Fe_(5)C_(2) formed during hydrogenation are beneficial for the C-C coupling reaction.The initial C-C coupling is related to the combination of CO species with the surface carbon of Fe/Co carbides,and the sustained C-C coupling is maintained by self-recovery of defective carbides.This new strategy contributes to the development of efficient catalysts for the hydrogenation of CO_(2) to value-added hydrocarbons.展开更多
Activated carbons calcined at 400˚C and 600˚C (AC-400 and AC-600), prepared using palm nuts, collected in the town of Franceville in Gabon, were used to study the dynamic adsorption of MnO<sub>4</sub>-<...Activated carbons calcined at 400˚C and 600˚C (AC-400 and AC-600), prepared using palm nuts, collected in the town of Franceville in Gabon, were used to study the dynamic adsorption of MnO<sub>4</sub>-</sup> ions in acidic media on fixed bed column and on the kinetic modeling of experimental data of breakthrough curves of MnO<sub>4</sub>-</sup> ions obtained. Results on the adsorption of MnO<sub>4</sub>-</sup> ions in fixed-bed dynamics obtained on AC-400 and AC-600 adsorbents beds indicated that the AC-400 bed appears to be the most efficient in removing MnO<sub>4</sub>-</sup> ions in acidic media. Indeed, the adsorbed amounts, the adsorbed capacities at saturation and the elimination percentage of MnO<sub>4</sub>-</sup> ions obtained with AC-400 (31.24 mg;52.06 mg·g<sup>-1</sup> and 41.65% respectively) were higher compared to those obtained with AC-600 (9.87 mg;16.45 mg·g<sup>-1</sup> and 17.79% respectively). The breakthrough curves kinetic modeling revealed that the Thomas model and the pseudo-first-order kinetic model were the most suitable models to describe the adsorption of MnO<sub>4</sub>-</sup> ions on adsorbents studied in our experimental conditions. The results of the intraparticle diffusion model showed that intraparticle diffusion was involved in the adsorption mechanism of MnO<sub>4</sub>-</sup> ions on investigated adsorbents and was not the limiting step and the only process controlling MnO<sub>4</sub>-</sup> ions adsorption. In contrast to AC-400, the intraparticle diffusion on AC-600 bed plays an important role in the adsorption mechanism of MnO<sub>4</sub>-</sup> ions.展开更多
文摘The preparation of a synthetic pitch from aromatic monomers could easily regulate structure orientation at the molecu-lar level,which would be useful in fabrication.An isotropic synthetic pitch was prepared by a chlorine-and/or nitrogen-induced sub-stitution polymerization reaction method using aromatic hydrocarbon precursors containing Cl and N,which for this study were chloromethyl naphthalene and quinoline.This method was verified by investigating the structural changes under different synthesis conditions,and the synthesis mechanism induced by aromatics containing Cl was also probed.The result shows that the pyridinic N in quinoline contains a lone pair of electrons,and is an effective active site to induce the polymerization reaction by coupling with aromatic hydrocarbons containing Cl.The reaction between such free radicals causes strong homopolymerization and oligomeriza-tion.A higher reaction temperature and longer reaction time significantly increased the degree of polymerization and thus increased the softening point of the pitch.A linear molecular structure was formed by the Cl substitution reaction,which produced a highly spinnable pitch with a softening point of 258.6℃,and carbon fibers with a tensile strength of 1163.82 MPa were obtained.This study provides a relatively simple and safe method for the preparation of high-quality spinnable pitch.
基金funding from the Key Research and Development Projects of Zhejiang Province(2022C01236)and the Ningbo Top Talent Project.
文摘Lignin-derived porous carbons have emerged as promising electrode materials for supercapacitors.However,the challenge remains in designing and controlling their structure to achieve ideal electrochemical performance due to the complex molecular structure of lignin and its intricate chemical reactions during the activation process.In this study,three porous carbons were synthesized from lignin by spray drying and chemical activation with vary-ing KOH ratios.The specific surface area and structural order of the prepared porous carbon continued to increase with the increase of the KOH ratio.Thermogravimetric-mass spectrometry(TG-MS)was employed to track the molecular fragments generated during the pyrolysis of KOH-activated lignin,and the mechanism of the thermochemical conversion was investigated.During the thermochemical conversion of lignin,KOH facili-tated the removal of H2 and CO,leading to the formation of not only more micropores and mesopores,but also more ordered carbon structures.The pore structure exhibited a greater impact than the carbon structure on the electrochemical performance of porous carbon.The optimized porous carbon exhibited a capacitance of 256 F g-1 at a current density of 0.2 A g-1,making it an ideal electrode material for high-performance supercapacitors.
基金supported by the National Natural Science Foundation of China (22379157,22179139)the Key Research and Development (R&D) Projects of Shanxi Province(202102040201003)+1 种基金the Research Program of Shanxi Province(202203021211203)the ICC CAS (SCJC-XCL-2023-10 and SCJC-XCL-2023-13)
文摘The chemical activation of various precursors is effective for creating additional closed pores in hard carbons for sodium storage.However,the formation mechanism of closed pores under the influence of pore-forming agents is not well understood.Herein,an effective chemical activation followed by a high-temperature self-healing strategy is employed to generate interconnected closed pores in lignin-derived hard carbon(HCs).By systematic experimental design combined with electron paramagnetic res-onance spectroscopy,it can be found that the content of free radicals in the carbon matrix influences the closure of open pores at high temperatures.Excessively high activation temperature(>700 C)leads to a low free radical concentration,making it difficult to achieve self-healing of open pores at high tempera-tures.By activation at 700°C,a balance between pore making and self-healing is achieved in the final hard carbon.A large number of free radicals triggers rapid growth and aggregation of carbon microcrys-tals,blocking pre-formed open micropores and creating additional interconnected closed pores in as-obtained hard carbons.As a result,the optimized carbon anode(LK-700-1300)delivers a high reversible capacity of 330.8 mA h g^(-1) at 0.03 A g^(-1),which is an increase of 86 mA h g^(-1) compared to the pristine lignin-derived carbon anode(L-700-1300),and exhibits a good rate performance(202.1 mA h g^(-1) at 1 A g^(-1)).This work provides a universal and effective guidance for tuning closed pores of hard carbons from otherprecursors.
基金the National Natural Science Foundation of China(52062012)Key Science&Technology Project of Hainan Province(ZDYF2020028)+2 种基金Key-Area Research and Development Program of Guangdong Province(2019B1102109003)the Innovation Team of Universities of Guangdong Province(2020KCXTD011)Guangdong Province Key Discipline Construction Project(2021ZDJS102).
文摘Sustainable energy conversion and storage technologies are a vital prerequisite for neutral future carbon.To this end,carbon materials with attractive features,such as tunable pore architecture,good electrical conductivity,outstanding physicochemical stability,abundant resource,and low cost,have used as promising electrode materials for energy conversion and storage.Defect engineering could modulate the structures of carbon materials,thereby affecting their electronic properties.The presence of defects on carbons may lead to asymmetric charge distribution,change in geometrical configuration,and distortion of the electronic structure that may result in unexpected electrochemical performances.In this review,recent advances in defects of carbons used for energy conversion and storage were examined in terms of types,regulation strategies,and fine characterization means of defects.The applications of such carbons in supercapacitors,rechargeable batteries,and electrocatalysis were also discussed.The perspectives toward the development of defect engineering carbons were proposed.In all,novel insights related to improvement in high-performance carbon materials for future energy conversion and storage applications were provided.
基金supported by the Natural Science Fund for Distinguished Young Scholars of Tianjin (17JCJQJC45500)the National Natural Science Foundation of China (NSFC,21876091 and 22178181)Tianjin Municipal Science and Technology Project (18PTZWHZ00150).
文摘In-situ MgO-doped ordered mesoporous carbon(OMC@MgO)was fabricated by formaldehyde-free self-assembly method,in which biomass-derived tannin was used as carbon precursor replacing fossil-based phenolics,Mg^(2+)as both cross-linker and precursor of catalytic sites.Up to~20 wt% MgO could be doped in the carbon skeleton with good dispersion retaining well-ordered mesoporous structures,while more MgO content(35 wt%)led to the failing in the formation of ordered mesoporous structure.The OMC@MgO possessed a high specific surface area(298.8 m^(2) g^(-1)),uniform pore size distribution(4.8 nm)and small crystallite size of MgO(1.73 nm)due to the confinement effect of ordered mesoporous structure.Using OMC@MgO as the heterogeneous catalyst,a maximum fructose yield of 32.4% with a selectivity up to 81.1%was achieved from glucose in water(90℃,60 min),which is much higher than that obtained using the MgO doped active carbon via conventional post-impregnation method(26.5%yield with 58.3% selectivity).Higher reaction temperature(>90℃)resulted in decrease of selectivity due to the formation of humins.The designed OMC@MgO displayed tolerant to high initial glucose concentrations(10 wt%)and could remain good recyclability without significant loss of activity for three cycles.
基金Funded by Natural Science Foundation of Shandong Province(No.ZR201702150018)China Postdoctoral Science Foundation Funding Scheme(No.2018M632747)+1 种基金the Fundamental Research Funds for the Central Universities(Nos.18CX02143A,17CX05017)New Faculty Start-up Funding from China University of Petroleum(No.YJ20170019).
文摘We employed the previously developed micro porous activated carbon models of different pore sizes ranges of 9-11?,10-12?,and 13-16?that were constructed by molecular simulation method based on a random packing of platelets of carbon sheets,functionalized with oxygen containing groups,to study the adsorption behavior of methane molecules.In studying methane adsorption behavior,we used Grand Canonical Monte Carlo and Molecular Dynamics methods at different temperatures of 273.15,298.15 and303.15 K.Adsorption isotherms,isosteric heats of adsorption,adsorption energy distributions and porosity changes of the models during adsorption process were analyzed and discussed.Furthermore,radial distribution Functions,relative distribution and diffusion coefficients of methane molecules in activated carbon models at different temperatures were studied.After the analysis,the main results indicated that large micro pores activated carbons were favorable for storing methane at lower temperatures and small micro pores were the most favorable for adsorbing methane molecules at higher temperatures.Interestingly,the developed model structures showed high capacities to store methane molecule at ambient temperatures and low pressure.
基金the support of the National Natural Science Foundation of China (20222809, 21978146)TsinghuaFoshan Innovation Special Fund (2021THFS0214)。
文摘Suzuki-Miyaura reaction of aryl halides with phenylboronic acid using a heterogeneous palladium catalyst based on activated carbons(AC) was systematically investigated in this work. Two different reaction modes(batch procedure and continuous-flow procedure) were used to study the variations of reaction processing. The heterogeneous catalysts presented excellent reactivity and recyclability for iodobenzene and bromobenzene substrates in batch mode, which can be attributed to stabilization of Pd nanoparticles by the thiol and amino groups on the AC supports. However, significant dehalogenation in the reaction mixture and Pd leaching from the heterogeneous catalysts were observed in continuous-flow mode.This unique phenomenon in continuous-flow mode resulted in a dramatic decline in reaction selectivity and durability of heterogeneous catalysts comparing with that of batch mode. In addition, the heterogeneous Pd catalysts with thiol-and amino-modified AC supports exhibited different reactivity and durability in batch and continuous-flow mode owing to the difference of interaction between Pd species and AC supports.
基金supported by the National Natural Science Foundation of China (22008098, 21978156, 42002040)the Program for Innovative Research Team (in Science and Technology) in University of Henan Province (21IRTSTHN004)+1 种基金the Program for Science & Technology Innovation Talents in Universities of Henan Province (22HASTIT008)the Foundation of State Key Laboratory of High-efficiency Utilization of Coal and Green Chemical Engineering (2022-K34)。
文摘Catalytic hydrogenation of CO_(2) using renewable hydrogen not only reduces greenhouse gas emissions,but also provides industrial chemicals.Herein,a Co-Fe bimetallic catalyst was developed by a facile reactive ball-milling method for highly active and selective hydrogenation of CO_(2) to value-added hydrocarbons.When reacted at 320℃,1.0 MPa and 9600 mL h^(-1) g_(cat)^(-1),the selectivity to light olefin(C_(2)^(=)-C_(4)^(=)) and C_(5)+ species achieves 57.3% and 22.3%,respectively,at a CO_(2) co nversion of 31.4%,which is superior to previous Fe-based catalysts.The CO_(2) activation can be promoted by the CoFe phase formed by reactive ball milling of the Fe-Co_(3)O_(4) mixture,and the in-situ Co_(2)C and Fe_(5)C_(2) formed during hydrogenation are beneficial for the C-C coupling reaction.The initial C-C coupling is related to the combination of CO species with the surface carbon of Fe/Co carbides,and the sustained C-C coupling is maintained by self-recovery of defective carbides.This new strategy contributes to the development of efficient catalysts for the hydrogenation of CO_(2) to value-added hydrocarbons.
文摘Activated carbons calcined at 400˚C and 600˚C (AC-400 and AC-600), prepared using palm nuts, collected in the town of Franceville in Gabon, were used to study the dynamic adsorption of MnO<sub>4</sub>-</sup> ions in acidic media on fixed bed column and on the kinetic modeling of experimental data of breakthrough curves of MnO<sub>4</sub>-</sup> ions obtained. Results on the adsorption of MnO<sub>4</sub>-</sup> ions in fixed-bed dynamics obtained on AC-400 and AC-600 adsorbents beds indicated that the AC-400 bed appears to be the most efficient in removing MnO<sub>4</sub>-</sup> ions in acidic media. Indeed, the adsorbed amounts, the adsorbed capacities at saturation and the elimination percentage of MnO<sub>4</sub>-</sup> ions obtained with AC-400 (31.24 mg;52.06 mg·g<sup>-1</sup> and 41.65% respectively) were higher compared to those obtained with AC-600 (9.87 mg;16.45 mg·g<sup>-1</sup> and 17.79% respectively). The breakthrough curves kinetic modeling revealed that the Thomas model and the pseudo-first-order kinetic model were the most suitable models to describe the adsorption of MnO<sub>4</sub>-</sup> ions on adsorbents studied in our experimental conditions. The results of the intraparticle diffusion model showed that intraparticle diffusion was involved in the adsorption mechanism of MnO<sub>4</sub>-</sup> ions on investigated adsorbents and was not the limiting step and the only process controlling MnO<sub>4</sub>-</sup> ions adsorption. In contrast to AC-400, the intraparticle diffusion on AC-600 bed plays an important role in the adsorption mechanism of MnO<sub>4</sub>-</sup> ions.