Three-dimensional (3D) nanoporous architectures, possessing high surface area, massive pores, and... more Three-dimensional (3D) nanoporous architectures, possessing high surface area, massive pores, and excellent structural stability, are highly desirable for many applications including catalysts and electrode materials in lithium ion batteries. However, the preparation of such materials remains a major challenge. Here, we introduce a novel method, instant gelation, for the synthesis of such materials. The as-prepared porous 3D MoS 2 @C nanocomposites, with layered MoS 2 clusters or strips ingrained in porous and conductive 3D carbon matrix, indeed showed excellent electrochemical performance when applied as anode materials for lithium ion batteries. Its interconnected carbon network ensures good conductivity and fast electron transport; the micro-, and mesoporous nature effectively shortens the lithium ion diffusion path and provides room necessary for volume expansion. The large specific surface area is beneficial for a better contact between electrode materials and electrolyte.
The success of polyacrylic acid (PAA) to suppress Li dendrite growth suggests that the mechanical... more The success of polyacrylic acid (PAA) to suppress Li dendrite growth suggests that the mechanical properties of polymer-based coatings, including the modulus, toughness, and interfacial adhesion are important design criteria. However, the measurement of the adhesion of thin PAA, as well as other polymer coatings to the reactive Li-metal anode surface is limited experimentally and challenging computationally. In this paper, a strategy was proposed to estimate the adhesion and delamination of the PAA(polymer)/Li interface, based on the bonding nature at the simpler PAA (oligomer)/Li interfaces using density functional theory calculations. It has been shown that the carboxylic acid groups in PAA reacted strongly with metallic Li, which significantly enhances the interfacial adhesion through the Li-O bonds formation, Li ionization and its incorporation into PAA, and -H or -OH termination of Li after decomposition of the COOH functional group. During delamination, it was found that the most likely PAA delamination route involved breaking partial Li-O bonds and lifting some ionized Li atoms from the Li-metal, especially for the Li atoms that showed a charge closer to +1 or are bonded with two O atoms from PAA. Based on the average bonding energies from PAA(oligomer)/Li interface delamination calculations, the work of separation, W sep , of the PAA(polymer)/Li interface was estimated to be ∼1.0 (J/m 2 ). The high W sep of PAA (polymer)/Li was comparable with the Li 2 O/Li interface and higher than Li 2 CO 3 /Li and LiF/Li interfaces. This order correlated well with the areal density of Li-O bonds, which can serve as a descriptor for the interfacial adhesion. This computational approach can be applied to other interfaces with polymer-based coatings.
h i g h l i g h t s g r a p h i c a l a b s t r a c t Hybrid Co x Ni 1Àx (OH) 2 nanosheets can be... more h i g h l i g h t s g r a p h i c a l a b s t r a c t Hybrid Co x Ni 1Àx (OH) 2 nanosheets can be prepared via a facile microwave-assisted route. The Co:Ni ratio depended size and crystal structure were demonstrated. The Co:Ni ratio depended electrochemical performance was proved. Co 0.2 Ni 0.8 (OH) 2 hexagonal nanosheets deliver a high specific capacitance of 1170 F g À1 at a current density of 4 A g À1 .
Precise control of structural parameters through nanoscale engineering to improve optical and ele... more Precise control of structural parameters through nanoscale engineering to improve optical and electronic properties of functional nanomaterials continuously remains an outstanding challenge. Previous work has been conducted largely at ambient pressure and relies on specific chemical or physical interactions such as van der Waals interactions, dipole-dipole interactions, chemical reactions, ligand-receptor interactions, etc. In this presentation, I will highlight our recent progress in development of a new Stress-Induced Fabrication method that uses mechanical compressive force applied to nanoparticles to induce structural phase transition and to consolidate new nanomaterials with precisely controlled structures and tunable properties. By manipulating nanoparticle coupling through external pressure, instead of through chemistry, a reversible change in their assemblies and properties can be achieved and demonstrated. In addition, over a certain threshold, the external pressure will force these nanoparticles into contact, thereby allowing the formation and consolidation of one-to three-dimensional nanostructures. Through stress induced nanoparticle assembly, materials engineering and synthesis become remarkably flexible without relying on traditional crystallization process where atoms/ions are locked in a specific crystal structure. Therefore, morphology or architecture can be readily tuned to produce desirable properties for practical applications.
In this project, we demonstrated the synthesis of polystyrene-polyvinylpyridyne (PS-PVP) micelles... more In this project, we demonstrated the synthesis of polystyrene-polyvinylpyridyne (PS-PVP) micelles, functionalization of these micelles to form organic/inorganic composite nanoparticles, and template directed assembly of dynamic PS-PVP micelles into features defined via soft nanoimprint lithography. We demonstrated unique assembly properties of dynamic micellar nanoparticles by combining a top down lithographic nanopatterning technique with a solutionbased bottom up self-assembly. The templates for the directed self-assembly of the micelles consisted of arrays of cylindrical recess features fabricated by nanoimprint lithography. Silica was coated on this patterned substrate and subsequently selectively functionalized with a positively charged molecular monolayer (N-(3-Trimethoxysilylpropyl) diethylenetriamine) to regulate the micelle-surface interactions. The self-assembled block co-polymer poly(styrene-b-4-vinyl pyridine), (PS 480k -PVP 145k ) micelles were approximately 325nm in diameter in aqueous solutions (pH = 2.5) and 50nm in diameter in the dry state. The average number of micelles assembled per feature increased from less than 1 to 12 with increasing feature diameter in the range of 200nm -1µm. Using a 2D model for maximum packing of circles in circular host features, the effective sphere size of the micelles during assembly was calculated to be 250nm in diameter. Thus, the micelles exhibited three characteristic sizes during assembly, 325nm in bulk solution, 250nm during assembly, and 50nm in the dry state. This dramatic variation in nanoparticle diameter during the assembly process offers unique opportunities for forming nanometer scale, multidimensional arrays not accessible using hard sphere building blocks.
The success of polyacrylic acid (PAA) to suppress Li dendrite growth suggests that the mechanical... more The success of polyacrylic acid (PAA) to suppress Li dendrite growth suggests that the mechanical properties of polymer-based coatings, including the modulus, toughness, and interfacial adhesion are important design criteria. However, the measurement of the adhesion of thin PAA, as well as other polymer coatings to the reactive Li-metal anode surface is limited experimentally and challenging computationally. In this paper, a strategy was proposed to estimate the adhesion and delamination of the PAA(polymer)/Li interface, based on the bonding nature at the simpler PAA (oligomer)/Li interfaces using density functional theory calculations. It has been shown that the carboxylic acid groups in PAA reacted strongly with metallic Li, which significantly enhances the interfacial adhesion through the Li-O bonds formation, Li ionization and its incorporation into PAA, and -H or -OH termination of Li after decomposition of the COOH functional group. During delamination, it was found that the most likely PAA delamination route involved breaking partial Li-O bonds and lifting some ionized Li atoms from the Li-metal, especially for the Li atoms that showed a charge closer to +1 or are bonded with two O atoms from PAA. Based on the average bonding energies from PAA(oligomer)/Li interface delamination calculations, the work of separation, W sep , of the PAA(polymer)/Li interface was estimated to be ∼1.0 (J/m 2 ). The high W sep of PAA (polymer)/Li was comparable with the Li 2 O/Li interface and higher than Li 2 CO 3 /Li and LiF/Li interfaces. This order correlated well with the areal density of Li-O bonds, which can serve as a descriptor for the interfacial adhesion. This computational approach can be applied to other interfaces with polymer-based coatings.
Porous structured silicon has been regarded as a promising candidate to overcome pulverization of... more Porous structured silicon has been regarded as a promising candidate to overcome pulverization of silicon-based anodes. However, poor mechanical strength of these porous particles has limited their volumetric energy density towards practical applications. Here we design and synthesize hierarchical carbon-nanotube@silicon@carbon microspheres with both high porosity and extraordinary mechanical strength (>200 MPa) and a low apparent particle expansion of ~40% upon full lithiation. The composite electrodes of carbon-nanotube@silicon@carbon-graphite with a practical loading (3 mAh cm−2) deliver ~750 mAh g−1 specific capacity, <20% initial swelling at 100% state-of-charge, and ~92% capacity retention over 500 cycles. Calendered electrodes achieve ~980 mAh cm−3 volumetric capacity density and <50% end-of-life swell after 120 cycles. Full cells with LiNi1/3Mn1/3Co1/3O2 cathodes demonstrate >92% capacity retention over 500 cycles. This work is a leap in silicon anode development...
Self-assembly techniques are powerful and efficient methods for the synthesis of nanoscale materi... more Self-assembly techniques are powerful and efficient methods for the synthesis of nanoscale materials. Using these techniques and their combination with other bottom-up fabrication processes, materials with hierarchical features can be produced with form and function in multiple length scales. We synthesize multifunctional nanoparticles through surfactant-assisted noncovalent interactions using nanoparticle building blocks. Self-assembly of these nano-building blocks results in functional materials that exhibit well-defined morphologies and hierarchical architectures for a wide range of applications. Hierarchically structured porphyrin nanocrystals can be synthesized through surfactant micelle-confined noncovalent interactions of photoactive porphyrins. We can amplify the intrinsic advantages of individual photoactive porphyrins by engineering them into well-defined active nanostructures. Through kinetic control, these nanocrystals exhibit precisely defined size, shape, and spatial arrangement of the individual porphyrins, which facilitates intermolecular mass and energy transfer. These self-assembly techniques provide remarkable flexibility to design morphologies and architectures that produce desirable properties for practical applications including photocatalysis, photodegradation, and phototherapy.
Lithium metal has great potential to become the anode for next generation of high-energy-density ... more Lithium metal has great potential to become the anode for next generation of high-energy-density batteries because of high capacity (3860 mAh g-1), lowest negative electrochemical potential, and low density. Low cycle efficiency and dendrite growth are two critical barriers for rechargeable batteries using Li metal as the anode, mainly due to the coupled mechanical/chemical degradation of the solid electrolyte interphase (SEI) layer formed on Li metal surface. In this work, we found a composite film of lithium aryl-silanolate with uniformly distributed sub-micron LiCldominant particles can in-situ form on Li metal surface by treating Li with a single phenyl substituted chlorosilane. The synergistic effect of the high modulus of the composite film resulted from both well dispersed LiCl particles and phenyl ring structures and the extra reinforcement by the π-π interaction of aryl silanolate molecules that coated on LiCl particles and Li electrode surface endows the artificial surface coating film with high modulus and stability, and thus suitable as an artificial SEI layer. The coin cells using the lithium metal electrodes with this Lithium silanolate/LiCl particle composite coating layer showed an improved cycle efficiency and the extended life in a relatively harsh cycling condition.
We report the hydrogen evolution reaction (HER) with molybdenum diselenide (MoSe 2) and its reduc... more We report the hydrogen evolution reaction (HER) with molybdenum diselenide (MoSe 2) and its reduced graphene oxide (rGO) hybrids synthesized by a microwave process followed by annealing at 400°C. The content of GO was varied to understand its role in the electrocatalytic activities. Electrochemical performance of the as-synthesized and the annealed catalysts underscores (i) a requirement of catalytic activation of the as-synthesized samples, (ii) an apparent shift in the onset potential as a result of annealing, and (iii) striking changes in the Tafel slope as well as the overpotential. The results clearly reveal that partially crystalline plain MoSe 2 is more elctroactive in comparison to its annealed counterpart, whereas annealing is advantageous to MoSe 2 /rGO. Improved HER performances of the annealed MoSe 2 /rGO hydrids arise from the synergistic effect between active MoSe 2 and rGO of improved conductivity. The annealed hybrid of MoSe 2 with rGO designated as MoSe 2 / rGO100_400°C demonstrated an excellent HER activity with a small onset potential of −46 mV vs reversible hydrogen electrode, a smaller Tafel slope (61 mV/dec), and a reduced overpotential of 186 mV at −10 mA/cm 2. As a result of a convenient synthetic process and the suitable electrocatalytic performance, this study would be beneficial to designing and fabricating other nanomaterials with/without a conductive support for their versatile applications.
Activated carbon (AC) with an extremely large specific surface area (2851m 2 /g) and large pore v... more Activated carbon (AC) with an extremely large specific surface area (2851m 2 /g) and large pore volume (2.68cm 3 /g) was derived from bio-waste oil tea shells by using ZnCl 2 as the activation agent. The porous carbon had a high amount of CO 2 adsorption (3.61mmol/g) at ambient conditions (25°C, 1bar). Comprehensive characterizations including XRD, Raman, SEM, TEM, and TGA proved graphite existed in the AC samples. However, the capacitance (146F/g @ 0.5A/g) was in the normal range of carbon materials. By coating with a thin layer of MnO 2 , the capacitance of MnO 2 /AC was enhanced significantly (1126F/g @ 0.5A/g) without sacrificing the rate capability and cycle stability, even though the surface area was reduced to 23m 2 /g and pore volume reduced to 0.05cm 3 /g. A twoelectrode (MnO 2 /AC//AC) supercapacitor cell was set up, the energy density reached 24Wh/kg with a power density of 275W/kg.
Three-dimensional (3D) nanoporous architectures, possessing high surface area, massive pores, and... more Three-dimensional (3D) nanoporous architectures, possessing high surface area, massive pores, and excellent structural stability, are highly desirable for many applications including catalysts and electrode materials in lithium ion batteries. However, the preparation of such materials remains a major challenge. Here, we introduce a novel method, instant gelation, for the synthesis of such materials. The as-prepared porous 3D MoS 2 @C nanocomposites, with layered MoS 2 clusters or strips ingrained in porous and conductive 3D carbon matrix, indeed showed excellent electrochemical performance when applied as anode materials for lithium ion batteries. Its interconnected carbon network ensures good conductivity and fast electron transport; the micro-, and mesoporous nature effectively shortens the lithium ion diffusion path and provides room necessary for volume expansion. The large specific surface area is beneficial for a better contact between electrode materials and electrolyte.
The success of polyacrylic acid (PAA) to suppress Li dendrite growth suggests that the mechanical... more The success of polyacrylic acid (PAA) to suppress Li dendrite growth suggests that the mechanical properties of polymer-based coatings, including the modulus, toughness, and interfacial adhesion are important design criteria. However, the measurement of the adhesion of thin PAA, as well as other polymer coatings to the reactive Li-metal anode surface is limited experimentally and challenging computationally. In this paper, a strategy was proposed to estimate the adhesion and delamination of the PAA(polymer)/Li interface, based on the bonding nature at the simpler PAA (oligomer)/Li interfaces using density functional theory calculations. It has been shown that the carboxylic acid groups in PAA reacted strongly with metallic Li, which significantly enhances the interfacial adhesion through the Li-O bonds formation, Li ionization and its incorporation into PAA, and -H or -OH termination of Li after decomposition of the COOH functional group. During delamination, it was found that the most likely PAA delamination route involved breaking partial Li-O bonds and lifting some ionized Li atoms from the Li-metal, especially for the Li atoms that showed a charge closer to +1 or are bonded with two O atoms from PAA. Based on the average bonding energies from PAA(oligomer)/Li interface delamination calculations, the work of separation, W sep , of the PAA(polymer)/Li interface was estimated to be ∼1.0 (J/m 2 ). The high W sep of PAA (polymer)/Li was comparable with the Li 2 O/Li interface and higher than Li 2 CO 3 /Li and LiF/Li interfaces. This order correlated well with the areal density of Li-O bonds, which can serve as a descriptor for the interfacial adhesion. This computational approach can be applied to other interfaces with polymer-based coatings.
h i g h l i g h t s g r a p h i c a l a b s t r a c t Hybrid Co x Ni 1Àx (OH) 2 nanosheets can be... more h i g h l i g h t s g r a p h i c a l a b s t r a c t Hybrid Co x Ni 1Àx (OH) 2 nanosheets can be prepared via a facile microwave-assisted route. The Co:Ni ratio depended size and crystal structure were demonstrated. The Co:Ni ratio depended electrochemical performance was proved. Co 0.2 Ni 0.8 (OH) 2 hexagonal nanosheets deliver a high specific capacitance of 1170 F g À1 at a current density of 4 A g À1 .
Precise control of structural parameters through nanoscale engineering to improve optical and ele... more Precise control of structural parameters through nanoscale engineering to improve optical and electronic properties of functional nanomaterials continuously remains an outstanding challenge. Previous work has been conducted largely at ambient pressure and relies on specific chemical or physical interactions such as van der Waals interactions, dipole-dipole interactions, chemical reactions, ligand-receptor interactions, etc. In this presentation, I will highlight our recent progress in development of a new Stress-Induced Fabrication method that uses mechanical compressive force applied to nanoparticles to induce structural phase transition and to consolidate new nanomaterials with precisely controlled structures and tunable properties. By manipulating nanoparticle coupling through external pressure, instead of through chemistry, a reversible change in their assemblies and properties can be achieved and demonstrated. In addition, over a certain threshold, the external pressure will force these nanoparticles into contact, thereby allowing the formation and consolidation of one-to three-dimensional nanostructures. Through stress induced nanoparticle assembly, materials engineering and synthesis become remarkably flexible without relying on traditional crystallization process where atoms/ions are locked in a specific crystal structure. Therefore, morphology or architecture can be readily tuned to produce desirable properties for practical applications.
In this project, we demonstrated the synthesis of polystyrene-polyvinylpyridyne (PS-PVP) micelles... more In this project, we demonstrated the synthesis of polystyrene-polyvinylpyridyne (PS-PVP) micelles, functionalization of these micelles to form organic/inorganic composite nanoparticles, and template directed assembly of dynamic PS-PVP micelles into features defined via soft nanoimprint lithography. We demonstrated unique assembly properties of dynamic micellar nanoparticles by combining a top down lithographic nanopatterning technique with a solutionbased bottom up self-assembly. The templates for the directed self-assembly of the micelles consisted of arrays of cylindrical recess features fabricated by nanoimprint lithography. Silica was coated on this patterned substrate and subsequently selectively functionalized with a positively charged molecular monolayer (N-(3-Trimethoxysilylpropyl) diethylenetriamine) to regulate the micelle-surface interactions. The self-assembled block co-polymer poly(styrene-b-4-vinyl pyridine), (PS 480k -PVP 145k ) micelles were approximately 325nm in diameter in aqueous solutions (pH = 2.5) and 50nm in diameter in the dry state. The average number of micelles assembled per feature increased from less than 1 to 12 with increasing feature diameter in the range of 200nm -1µm. Using a 2D model for maximum packing of circles in circular host features, the effective sphere size of the micelles during assembly was calculated to be 250nm in diameter. Thus, the micelles exhibited three characteristic sizes during assembly, 325nm in bulk solution, 250nm during assembly, and 50nm in the dry state. This dramatic variation in nanoparticle diameter during the assembly process offers unique opportunities for forming nanometer scale, multidimensional arrays not accessible using hard sphere building blocks.
The success of polyacrylic acid (PAA) to suppress Li dendrite growth suggests that the mechanical... more The success of polyacrylic acid (PAA) to suppress Li dendrite growth suggests that the mechanical properties of polymer-based coatings, including the modulus, toughness, and interfacial adhesion are important design criteria. However, the measurement of the adhesion of thin PAA, as well as other polymer coatings to the reactive Li-metal anode surface is limited experimentally and challenging computationally. In this paper, a strategy was proposed to estimate the adhesion and delamination of the PAA(polymer)/Li interface, based on the bonding nature at the simpler PAA (oligomer)/Li interfaces using density functional theory calculations. It has been shown that the carboxylic acid groups in PAA reacted strongly with metallic Li, which significantly enhances the interfacial adhesion through the Li-O bonds formation, Li ionization and its incorporation into PAA, and -H or -OH termination of Li after decomposition of the COOH functional group. During delamination, it was found that the most likely PAA delamination route involved breaking partial Li-O bonds and lifting some ionized Li atoms from the Li-metal, especially for the Li atoms that showed a charge closer to +1 or are bonded with two O atoms from PAA. Based on the average bonding energies from PAA(oligomer)/Li interface delamination calculations, the work of separation, W sep , of the PAA(polymer)/Li interface was estimated to be ∼1.0 (J/m 2 ). The high W sep of PAA (polymer)/Li was comparable with the Li 2 O/Li interface and higher than Li 2 CO 3 /Li and LiF/Li interfaces. This order correlated well with the areal density of Li-O bonds, which can serve as a descriptor for the interfacial adhesion. This computational approach can be applied to other interfaces with polymer-based coatings.
Porous structured silicon has been regarded as a promising candidate to overcome pulverization of... more Porous structured silicon has been regarded as a promising candidate to overcome pulverization of silicon-based anodes. However, poor mechanical strength of these porous particles has limited their volumetric energy density towards practical applications. Here we design and synthesize hierarchical carbon-nanotube@silicon@carbon microspheres with both high porosity and extraordinary mechanical strength (>200 MPa) and a low apparent particle expansion of ~40% upon full lithiation. The composite electrodes of carbon-nanotube@silicon@carbon-graphite with a practical loading (3 mAh cm−2) deliver ~750 mAh g−1 specific capacity, <20% initial swelling at 100% state-of-charge, and ~92% capacity retention over 500 cycles. Calendered electrodes achieve ~980 mAh cm−3 volumetric capacity density and <50% end-of-life swell after 120 cycles. Full cells with LiNi1/3Mn1/3Co1/3O2 cathodes demonstrate >92% capacity retention over 500 cycles. This work is a leap in silicon anode development...
Self-assembly techniques are powerful and efficient methods for the synthesis of nanoscale materi... more Self-assembly techniques are powerful and efficient methods for the synthesis of nanoscale materials. Using these techniques and their combination with other bottom-up fabrication processes, materials with hierarchical features can be produced with form and function in multiple length scales. We synthesize multifunctional nanoparticles through surfactant-assisted noncovalent interactions using nanoparticle building blocks. Self-assembly of these nano-building blocks results in functional materials that exhibit well-defined morphologies and hierarchical architectures for a wide range of applications. Hierarchically structured porphyrin nanocrystals can be synthesized through surfactant micelle-confined noncovalent interactions of photoactive porphyrins. We can amplify the intrinsic advantages of individual photoactive porphyrins by engineering them into well-defined active nanostructures. Through kinetic control, these nanocrystals exhibit precisely defined size, shape, and spatial arrangement of the individual porphyrins, which facilitates intermolecular mass and energy transfer. These self-assembly techniques provide remarkable flexibility to design morphologies and architectures that produce desirable properties for practical applications including photocatalysis, photodegradation, and phototherapy.
Lithium metal has great potential to become the anode for next generation of high-energy-density ... more Lithium metal has great potential to become the anode for next generation of high-energy-density batteries because of high capacity (3860 mAh g-1), lowest negative electrochemical potential, and low density. Low cycle efficiency and dendrite growth are two critical barriers for rechargeable batteries using Li metal as the anode, mainly due to the coupled mechanical/chemical degradation of the solid electrolyte interphase (SEI) layer formed on Li metal surface. In this work, we found a composite film of lithium aryl-silanolate with uniformly distributed sub-micron LiCldominant particles can in-situ form on Li metal surface by treating Li with a single phenyl substituted chlorosilane. The synergistic effect of the high modulus of the composite film resulted from both well dispersed LiCl particles and phenyl ring structures and the extra reinforcement by the π-π interaction of aryl silanolate molecules that coated on LiCl particles and Li electrode surface endows the artificial surface coating film with high modulus and stability, and thus suitable as an artificial SEI layer. The coin cells using the lithium metal electrodes with this Lithium silanolate/LiCl particle composite coating layer showed an improved cycle efficiency and the extended life in a relatively harsh cycling condition.
We report the hydrogen evolution reaction (HER) with molybdenum diselenide (MoSe 2) and its reduc... more We report the hydrogen evolution reaction (HER) with molybdenum diselenide (MoSe 2) and its reduced graphene oxide (rGO) hybrids synthesized by a microwave process followed by annealing at 400°C. The content of GO was varied to understand its role in the electrocatalytic activities. Electrochemical performance of the as-synthesized and the annealed catalysts underscores (i) a requirement of catalytic activation of the as-synthesized samples, (ii) an apparent shift in the onset potential as a result of annealing, and (iii) striking changes in the Tafel slope as well as the overpotential. The results clearly reveal that partially crystalline plain MoSe 2 is more elctroactive in comparison to its annealed counterpart, whereas annealing is advantageous to MoSe 2 /rGO. Improved HER performances of the annealed MoSe 2 /rGO hydrids arise from the synergistic effect between active MoSe 2 and rGO of improved conductivity. The annealed hybrid of MoSe 2 with rGO designated as MoSe 2 / rGO100_400°C demonstrated an excellent HER activity with a small onset potential of −46 mV vs reversible hydrogen electrode, a smaller Tafel slope (61 mV/dec), and a reduced overpotential of 186 mV at −10 mA/cm 2. As a result of a convenient synthetic process and the suitable electrocatalytic performance, this study would be beneficial to designing and fabricating other nanomaterials with/without a conductive support for their versatile applications.
Activated carbon (AC) with an extremely large specific surface area (2851m 2 /g) and large pore v... more Activated carbon (AC) with an extremely large specific surface area (2851m 2 /g) and large pore volume (2.68cm 3 /g) was derived from bio-waste oil tea shells by using ZnCl 2 as the activation agent. The porous carbon had a high amount of CO 2 adsorption (3.61mmol/g) at ambient conditions (25°C, 1bar). Comprehensive characterizations including XRD, Raman, SEM, TEM, and TGA proved graphite existed in the AC samples. However, the capacitance (146F/g @ 0.5A/g) was in the normal range of carbon materials. By coating with a thin layer of MnO 2 , the capacitance of MnO 2 /AC was enhanced significantly (1126F/g @ 0.5A/g) without sacrificing the rate capability and cycle stability, even though the surface area was reduced to 23m 2 /g and pore volume reduced to 0.05cm 3 /g. A twoelectrode (MnO 2 /AC//AC) supercapacitor cell was set up, the energy density reached 24Wh/kg with a power density of 275W/kg.
Uploads
Papers by binsong li