Porous Amorphous Carbon Research Articles

Coral–like Ni2P@C derived from metal–organic frameworks with superior electrochemical performance for hybrid supercapacitors

Transition metal phosphides (TMPs), used in hybrid supercapacitors (HSCs) as battery–type electrodes, have gain tractions for balancing the requirements for both power and energy; however, their poor structural integrity, inferior conductivity and low porosity restrict the achievable performance. Developing an elaborate material architecture for electrodes that endows mechanical robustness, superior conductivity and large surface area is a pressing need for TMPs to achieve boosted performance in supercapacitors. Here, we report a coral–like interconnected Ni2P nanoparticles dispersed on porous amorphous carbon matrix (Ni2P@C) as the electrode material with superior electrochemical performance. The Ni2P@C electrode exhibits a superior specific capacity of 3,631mC cm−2 at 1 mA cm−2 (979 C g−1 at 1 A g−1). Impressively, the assembly of Ni2P@C and active carbon (AC) electrodes result in an advanced HSC with energy density of 44.0 Wh kg−1 at 800 W kg−1 and cycling stability of 90.5% retention after 10,000 cycles, demonstrating this unique Ni2P@C structure is promising for developing practical HSC technology.

Recycling diesel soot nanoparticles for use as activated carbon in Li ion batteries

We report the successful capture and reuse of diesel exhaust soot particles as a conductive additive in lithium manganese oxide (LMO) and lithium iron phosphate (LFP) cathodes in Li-ion batteries. This approach enables an abundant toxic pollutant to be converted into a valuable material for energy storage devices. This study consists of an initial characterization of the diesel soot particles, a high-temperature annealing step to remove residual organics and unburned hydrocarbons, and characterization of the electrical performance in a Li-ion battery configuration. Here, composite electrodes are fabricated by mixing active materials (LFP or LMO) with conductive carbon and binders. The performance of the diesel soot particles as conductive additives is compared with that of commercially available activated carbon (i.e., Super P®). The current evolution of the composite electrode made with diesel soot particles demonstrates comparable performance to the electrodes containing the Super P® carbon. Based on high-resolution transmission electron microscope (HRTEM) images and scanning mobility particle sizer (SMPS) spectra, we find that these diesel soot nanoparticles follow a narrow log-normal distribution centered around 100 nm in diameter and consist of highly porous amorphous carbon, which provide a large surface-to-volume ratio, making them ideal candidates for electrode materials in Li ion batteries.

3D Bimodal Porous Amorphous Carbon with Self-Similar Porosity by Low-Temperature Sequential Chemical Dealloying

Synthesizing 3D porous carbon with atomic-scale control in geometry and topology of porous architectures is of great significance while it technically remains challenging. Dealloying, the selective...

Humic acid resin-based amorphous porous carbon as high rate and cycle performance anode for sodium-ion batteries

We developed amorphous porous carbon (i.e. humic acid resin-based amorphous porous carbon, HARC800) with the controlled porosity in the ordered structure as anode material for sodium-ion batteries (SIBs) through the optimized annealing process supported by functional lignite and sodium alginate precursors. HARC800 has well-developed interconnected mesoporous and micropores, accounting for 85.7% and 14.3%, respectively. The porous characteristic of amorphous carbon materials can curtail the diffusion path of Na+, and promote the penetration of electrolyte in the material, which is very instrumental in intensify the dynamic property of the material, thereby promoting the storage of Na+. When it is applied to the anode for SIBs, the HARC800 provides an initial reversible capacity of 260 mA h g−1 at 30 mA g−1. Even at 2000 mA g−1, it appears 99 mA h g−1, indicating that it has excellent rate performance. It could be yielded 133 mA h g−1 after 200 cycles at 500 mA g−1, and maintain 119 mA h g−1 after 1000 cycles at 1000 mA g−1, suggesting its outstanding long-life cycle performance. This research proposes that reasonable control of the ratio of mesoporous and micropores can promote the Na+ storage performance of amorphous porous carbon materials.

3C-SiC axis nanowires generated during the pyrolysis of diamond/SiC composite green body

3C-SiC axis nanowires were produced during the diamond/SiC composite green body pyrolysis. The morphology and microstructure of the 3C-SiC axis nanowires and diamond/SiC composite blank were observed by scanning electron microscope and transmission electron microscope. The compositions of the 3C-SiC axis nanowires and diamond/SiC composite blank were characterized by X-ray diffraction and X-ray photoelectron spectroscopy. The pore size and the pore size distribution of the green body and pyrolyzed body were measured using the mercury intrusion porosimeter (MIP) method. The results showed that the 3C-SiC axis nanowires were coated with a SiOx amorphous layer. The nanowires varied in length, and their diameters lied in the range of 25–35 nm. The pore diameters of the green body and pyrolyzed body are 10–26 μm and 0.5–25 μm, respectively. The generation of nanowires leads to a decrease in the pore size of the pyrolyzed body. The increase in porosity of the pyrolyzed body was caused by the formation of porous amorphous hard carbon by the pyrolysis of phenolic resin.

TiO2 decorated porous carbonaceous network structures offer confinement, catalysis and thermal conductivity for effective hydrogen storage of LiBH4

Lithium borohydride (LiBH4), with a high theoretical capacity of 18.4 wt%, is one of the most promising materials for solid–state hydrogen storage. However, it suffers from too high an operation temperature and poor reversibility. Here, a synergetic approach is developed to improve the properties. An active porous core–shell network structure is constructed as a scaffold for LiBH4–with carbon nanotube (CNT) as the core and nano–TiO2 decorated porous amorphous carbon as the shell (CNT@PC@TiO2) with an optimized fraction of TiO2. The hybrid scaffold possesses high porosity, large specific surface area and small pore sizes, for effective confinement of LiBH4 by a melt infiltration method and high loadings of LiBH4 up to 50–70 wt%, with enhanced interface diffusion and reaction without agglomeration; TiO2 reacts with LiBH4 during the infiltration process, to form LiTiO2 and TiB2 as the catalysts for LiBH4, and the CNTs facilitate heat management. The confined LiBH4 system shows considerable improvement of hydrogen sorption properties. At a LiBH4 loading of 60 wt%, the system releases 7.3 wt% H2 within 60 min at 320 °C, and a reversible capacity of 5.1 wt% is maintained even after 20 cycles. The present study provides further insight into the rational design and utilization of the synergetic effects of nanoconfinement, catalysis, surface interaction and thermal transfer to improve the overall hydrogen storage performance of LiBH4.

The Use of Mechanical Activation of Polyvinyl Chloride in the Presence of Alkalis for Synthesis of Porous Carbon Materials

The synthesis of porous carbon materials was carried out by mechanochemical dehydrochlorination of polyvinyl chloride in the presence of alkalis (KOH, LiOH) using a high-energy planetary mill and the subsequent two-stage heat treatment of the obtained polyvinylenes (polymers with a conjugated double bond system)—carbonization to 400°C and carbon dioxide at 850°C or alkaline activation and 800°C, respectively. The structure of the obtained products was studied by Raman spectroscopy and transmission electron microscopy, analysis of isotherms of low-temperature adsorption/desorption of nitrogen. The resulting products are (micro-, meso-) porous amorphous carbon materials with specific surface SBET from 460 to 605 m2/g, micropore volume from 0.09 to 0.21 cm3/g, and mesopore volume from 0.09 to 0.6 cm3/g

Onion Peel Based Porous Carbons As Cathode Components for LiS Battery

In recent years, lithium-sulfur (LiS) battery has emerged as promising energy storage systems to replace the conventional lithium ion battery. This battery system uses elemental sulfur as cathodes and Li metal as anodes and possess a higher specific capacity (1,675 mAh/g) compared to that of lithium ion battery. However, some technical problems such as the low conductivity of sulfur, huge volume expansion during cycling and the shuttle effect of polysulfide have prevented this kind of battery system to be commercialized. One method to solve those problems is by using carbon materials as cathode component together with sulfur to form Carbon-sulfur composite cathodes. Carbon materials could improve the electrochemical performance of LiS battery due to the electrical conductivity and highly porous structure. Biomass derived conductive carbon materials have attracted increasing attention on account of their abundance, sustainability, and easy accessibility. Here, onion peel waste has been utilized to synthesize amorphous porous carbon (OPWC) as cathode component for LiS battery. Porous carbons were prepared by using hydrothermal carbonization followed by the chemical activation process using KOH. The carbon-sulfur composites were then obtained after sulfur loading using the melt diffusion method. As obtained OPWC/S composite demonstrates stable cycle performance and a reversible specific capacity of 630 mAh/g after 100 cycles at current density of 0.1 C when used for LiS battery.

Multi-forks hierarchical porous amorphous carbon with N-Doping for high-performance potassium-ion batteries

Graphitic carbon with high electronic conductivity has been widespreadly reported as an anode material for potassium-ion batteries (PIBs). However, it cannot accommodate more K ions and alleviate huge volume variations during cycling due to a narrow interlayer spacing of 0.335 nm, resulting in poor electrochemical behavior. Herein, by rational design, N-doping multi-forks amorphous carbon with hierarchical pores (NCTS) was successfully fabricated. The obtained NCTS exhibited enlarged interlayer spacing (0.376 nm), high specific surface area (396.6 m2 g−1), and well developed unique porous structure. These features can reduce the diffusion distance for both ions and electrons, and maintain the stability of the electrode structure. Hence, the NCTS electrode exhibits remarkable electrochemical performance with high specific capacity of 350.3 mA h g−1 at 500 mA g−1, ultra-long lifespan (over 2000 cycles at 2000 mA g−1), and outstanding rate capability (292.3 mA h g−1 at 1000 mA g−1). This work provides efficient guidance for constructing high-performance carbon anode materials to storage potassium.

Effective Trapping of Polysulfides Using Functionalized Thin-Walled Porous Carbon Nanotubes as Sulfur Hosts for Lithium-Sulfur Batteries.

Owing to their high aspect ratios and structures of high-mechanical-strength conductive scaffolds, carbon nanotubes (CNTs) are considered to be one of the most promising hosts for sulfur in lithium-sulfur batteries (LSBs). However, traditional CNTs with impermeable walls are not conducive to the penetration of sulfur, resulting in a large number of sulfur exposures to the electrolyte. Therefore, it is difficult to effectively limit the shuttle effect of polysulfides. Here, a kind of thin-walled porous amorphous carbon nanotube (HCNT) is adopted as the host for sulfur in LSBs. To further alleviate the shuttle effect, oxygen-containing functional groups (OCFGs) are introduced to modify HCNTs to form HOCNTs. The S/HOCNT composite with the embedded structure is successfully constructed. The S/HOCNT cathode demonstrates glorious cycling and rate performance (798.5 mAh g-1 at 0.2 C after 100 cycles and 511.6 mAh g-1 at 1 C after 500 cycles). The excellent electrochemical performance of S/HOCNT can be attributed to the embedded structure of sulfur in HOCNTs, which avoids direct contact with the electrolytes and strong bonding action of OCFGs and polysulfides, effectively limiting the shuttle effect of polysulfides.

Onion Peel Based Porous Carbons As Cathode Components for Lis Battery

In recent years, Lithium-sulfur (LiS) battery has emerged as promising energy storage systems to replace the conventional lithium ion battery. This battery system uses elemental sulfur as cathodes and Li metal as anodes and possess a higher specific capacity (1675 mAh/g) compared to that of lithium ion battery. However, some technical problems such as the low conductivity of sulfur, huge volume expansion during cycling and the shuttle effect of polysulfide have prevented this kind of battery system to be commercialized. One method to solve those problems is by using carbon materials as cathode component together with sulfur to form Carbon-sulfur composite cathodes. Carbon materials could improve the electrochemical performance of LiS battery due to the electrical conductivity and highly porous structure. Biomass derived conductive carbon materials have attracted increasing attention on account of their abundance, sustainability, and easy accessibility. Here, onion peel waste has been utilized to synthesize amorphous porous carbon (OPC) as cathode component for LiS battery. Porous carbons were prepared by using hydrothermal carbonization followed by the chemical activation process using KOH. The carbon-sulfur composites were then obtained after sulfur loading using the melt diffusion method. As obtained OPC/S composite demonstrates stable coulombic efficiencies of 98% and a reversible specific capacity of 432 mAh/g after 100 cycles at current density of 0.1 C when used for LiS battery. These improved electrochemical performances may be attributed to the structure of OPC showing mesoporous structure with defect carbon structure and high specific surface areas. These results show the potential and promising application of onion peel waste based porous carbon in LiS battery.

A Nano-Rattle SnO2@carbon Composite Anode Material for High-Energy Li-ion Batteries by Melt Diffusion Impregnation.

The huge volume expansion in Sn-based alloy anode materials (up to 360%) leads to a dramatic mechanical stress and breaking of particles, resulting in the loss of conductivity and thereby capacity fading. To overcome this issue, SnO2@C nano-rattle composites based on <10 nm SnO2 nanoparticles in and on porous amorphous carbon spheres were synthesized using a silica template and tin melting diffusion method. Such SnO2@C nano-rattle composite electrodes provided two electrochemical processes: a partially reversible process of the SnO2 reduction to metallic Sn at 0.8 V vs. Li+/Li and a reversible process of alloying/dealloying of LixSny at 0.5 V vs. Li+/Li. Good performance could be achieved by controlling the particle sizes of SnO2 and carbon, the pore size of carbon, and the distribution of SnO2 nanoparticles on the carbon shells. Finally, the areal capacity of SnO2@C prepared by the melt diffusion process was increased due to the higher loading of SnO2 nanoparticles into the hollow carbon spheres, as compared with Sn impregnation by a reducing agent.

Adsorption-doping for preparing N-doped porous carbon for promising electrochemical capacitors-using peptone and polymer porous resin as precursors

The adsorption-doping has been shown an effective strategy for preparing nitrogen doped porous carbons. In the present study, commercial porous polymer spherical resin was used as adsorbent, and nitrogenous organic-peptone was employed to be the nitrogen source. Adsorption, carbonization and chemical etching were sequentially proceeded. Elements contents of nitrogen and oxygen in the obtained amorphous porous carbon were 2.93 at.% and 4.85 at.%, respectively. The specific surface area was 1,425 m2 g−1, of which the contribution mainly came from micropores with size of 4–7 Å. As an electroactive material, electrodes enclosed the porous carbon harvested specific capacitances of 343.9 and 253.5 F g−1 at a current density of 1 A g−1 in the three-electrode and symmetric-two-electrode systems, respectively. In basic aqueous electrolyte, the supercapacitor device achieved a maximum specific energy of 9.1 W h kg−1 at a specific power of 123.2 W kg−1. Findings of the study further illustrate the feasibility of the adsorption doping strategy. Results also acknowledged that the strategy could be used as a universal process to develop promising porous carbon materials for high performances supercapacitors.

Microwave Absorption of Crystalline Fe/MnO@C Nanocapsules Embedded in Amorphous Carbon

HighlightsThe crystalline Fe/MnO@C core–shell nanocapsules embedded in porous amorphous carbon matrix (FMCA) was prepared by a novel confinement strategy of modified arc-discharge method.The heterogeneous crystalline–amorphous nanocrystals disperse evenly and exhibit improvement of static magnetization and excellent electromagnetic absorption properties.The adding MnO2 confines degree of graphitization and contributes to form amorphous carbon. Dielectric loss and microwave absorption are achieved adjustable.

Enhanced photoelectrocatalytic activity of direct Z-scheme porous amorphous carbon nitride/manganese dioxide nanorod arrays

Carbon nitride (C3N4) is a promising photocatalyst that can be applied in environmental remediation and energy conversion. However, the absorption range and charge separation efficiency of C3N4 are still severely restricted for its large-scale practical applications. Herein, we demonstrate a simple thermal polymerization and electrodeposition method, followed by partial etching strategy to synthesize direct Z-scheme porous zinc oxide/amorphous carbon nitride/manganese dioxide hybrid core-shell nanorod array (denoted as P-ZnO/ACN/MnO2) by encapsulating amorphous carbon nitride layers (ACN) and manganese dioxide nanosheets (MnO2) on the zinc oxide nanorod arrays (denoted as ZnO). Interestingly, ZnO serves as the collector of charge carriers and MnO2 plays a significant role in protecting ACN from corrosion. The as-prepared Z-scheme P-ZnO/ACN/MnO2 heterojunction exhibits high photocurrent density of 5.2 mA cm−2 at 0.6 V vs. Ag/AgCl, high photoconversion efficiency 0.98%, and universal photoelectrocatalytic degradation activity for degradation of organic dyes under visible light irradiation. The band gap energy and conduction band position of ZnO, ACN and MnO2 are calculated by UV–visible diffuse reflection and Mott-Schottky measurement, which strongly support the direct Z-scheme charge carrier migration mechanism. This finding provides an efficient strategy to construct highly active and stable C3N4-based Z-scheme photocatalytic system.

Amorphous MnO₂ on Carbon Substrate with Ordered Submicron Pore Array Structure for High Performance Supercapacitor Electrode.

MnO₂/C composite with ordered submicron pore array structure was obtained by using Atrophaneura horishana butterfly wings as template and carbon source for high performance supercapacitor electrode. Micro/nanostructured carbon substrate was firstly constructed by calcining the wing specimen under nitrogen atmosphere. Then, amorphous MnO₂ was formed on the structure via surface solution reaction. The as-prepared composite shows a high specific capacitance of 1342 F g-1 at 1 A g-1 with good rate capability and stability. The excellent charge-discharge performance should be attributed to the coupling effect of pseudocapacitive amorphous MnO₂ and robust porous carbon. The pore array structured substrate not only provides high specific surface area for sufficient active sites, but also exhibits good connectivity for efficient charge and mass transport.

Enhanced photoelectrochemical hydrogenation of green-house gas CO2 to high-order solar fuel on coordinatively unsaturated metal-N sites containing carbonized Zn/Co ZIFs

Porous carbon-based catalysts facilitate CO2 photoelectrochemical reduction reaction (CO2PRR) through the high charge transfer ability and CO2 adsorption ability. However, the design of catalysts with high selectivity towards high-order solar fuels (such as ethanol and propanol) remains challenging. Herein, catalysts of carbonized Zn/Co Zeolitic Imidazolat Frameworks with various pyrolysis hours (xh-C-Zn/Co ZIFs) were synthesized and accessed for high selective CO2PRR for the first time. XRD and TEM analyses show that the C containing functional groups in pristine Zn/Co ZIF are carbonized and turned into amorphous porous carbon, while many Co and ZnO nanoparticles are formed during the pyrolysis process. Electrochemical characterizations of the catalysts prove that increasing pyrolysis time of Zn/Co ZIF from 1 h to 3 h, resulting in a decreased light current density from 3.3 mA/cm2 to 2.3 mA/cm2, which is much higher than that of Zn/Co ZIF (1.9 mA/cm2). Meanwhile, increasing pyrolysis time of Zn/Co ZIF from 1 h to 3 h results in decreased BET surface area and CO2 adsorption ability. XPS spectra suggest a decreased content of metal-nitrogen bonds in C–Zn/Co ZIF, which leads to the formation of coordinatively unsaturated metal-nitrogen sites. Density functional theory (DFT) calculations reveal that the coordinatively unsaturated CoN3V sites in C–Zn/Co ZIF had the highest catalytic activity towards high-order organics. The total carbon atom conversion rate reaches 5459 nmol/h·cm2 when 1h-C-Zn/Co ZIF is employed as catalyst in the CO2PRR system and the selectivity towards high-order solar fuel reaches 84%.

Tuning the inner hollow structure of lightweight amorphous carbon for enhanced microwave absorption

Herein, we demonstrate that amorphous carbon can be converted to lightweight superior MA materials only via a facile inside three dimensional ordered hollow (3DOH) architecture fabrication. The as-fabricated 3DOH carbon (3DOHC) blocks consist of ordered spherical voids formed by connected thin porous amorphous carbon walls. The diameter of the voids has a great influence on the MA performance, and a minimum reflection loss (RL) value of −66.24 dB is observed at 15.68 GHz for the 3DOHC blocks with inside void diameter of 500 nm (3DOHC-500) at a low filling rate of 5.0 wt% and absorber thickness of 1.6 mm. Moreover, the widest absorption bandwidth for RL values below −10 dB is 4.78 GHz when the absorber thickness is 1.7 mm while still keeping a low RL value of −45.85 dB. The enhancement of the MA performance of 3DOHC-500 based absorber can be attributed to the synergic effect of dielectric loss and impedance matching. The excellent MA performance combining with the low filling rates (2.5–5.0 wt%), thin thickness and lightweight (≤100 mg/cm−3) makes these 3DOHC-500 very promising candidate for practical MA applications.

Preparation and electrochemical properties of biochar from pyrolysis of pomelo peel via different methods

Dried pomelo peel waste was employed as raw material and heated separately via three different thermal treatment methods which are vacuum tube furnace (700 °C, 300 ∼ 1 × 10−5 Pa), muffle furnace (300 °C in air) and hydrothermal treatment in an oven (200 °C, sealed). Therefore, three kinds of amorphous porous carbon were obtained and named as S1, S2 and S3, respectively. XRD, SEM, EDS, specific surface area and pore size analyzer have been used to characterize the morphology, composition and porosity of the biochar materials which show 3 dimensional porous framework morphologies, but only S1 possesses highest specific surface area (464.96m2/g) among the 3 biochar materials. The electrochemical properties were characterized via galvanostatic charge/discharge method, cyclic voltammetry (CV) and AC impedance. After 100 cycles of charge and discharge process, the specific capacity of the biochar S1 maintained 297.0mAh/g. The specific capacity of S2 was 103.3mAh/g and the specific capacity of S3 is 106.0mAh/g. Thus, S1 exhibits a high specific surface area and excellent electrochemical performance which may have potential application due to low cost of the biochar prepared from pomelo peel wastes.

Constructing a tunable heterogeneous interface in bimetallic metal-organic frameworks derived porous carbon for excellent microwave absorption performance

Designing pure carbonaceous microwave absorbers with strong absorption capability and broad effective absorption bandwidth (EAB) is still a challenge for efficient microwave absorption. Here, a kind of bimetallic metal-organic frameworks derived porous amorphous carbon particle with hollow graphene spheres confined in it (HGS@PAC), was prepared by the controlled annealing process. The thickness of hollow graphene spheres could be tuned from 9 graphene layers to 24 graphene layers by adjusting the annealing time, and thereby tuning their dielectric properties. The minimum RC of the optimized HGS@PAC reaches −56 dB at 3.5 GHz with a thickness of 6.75 mm, indicating its strong microwave absorption performance. In addition, the widest EAB reaches 5.6 GHz (12.4–18 GHz) with a thickness of only 1.85 mm. It is important to highlight that the EAB can cover the whole measured bandwidth (2–18 GHz) with the sample thickness ranging from 1.85 mm to 10 mm. The enhanced microwave attenuation ability can be ascribed to the enhanced interfacial polarization, dipole polarization, and conductive loss, resulting from the designed unique architectures.