Self-supporting Carbon Research Articles

Self-supported hierarchical crystalline carbon nitride arrays with triazine-heptazine heterojunctions for highly efficient photoredox catalysis

Self-supported hierarchical crystalline carbon nitride arrays (MA-rod array), which show the excellent properties of photocatalytic hydrogen evolution and oxidative organic synthesis, were synthesized by molten salt-assisted pyrolysis of rod-like supramolecular precursors from the hydrolysis of melamine. On the nanoscale, the highly crystalline MA-rod array has an omasum-like architecture with combined advantages of rapid electrolyte diffusion, efficient gas evolution, fast electronic transmission, and lower interface resistance. At the molecular level, the triazine-heptazine heterojunctions remarkably improve charge carrier transfer and separation. In the tests of photoredox catalysis, the MA-rod array exhibited 51-fold higher hydrogen production rate (11720 μmol h−1 gcat-1) than the reference with a high apparent quantum yield (AQY) of 60% at 420 nm. Furthermore, the oxidation of aromatic hydrocarbons to aldehydes or ketones can be obtained under single wavelength (460 nm) irradiation with milligram yields (e.g., the isolated yield of benzaldehyde is 34.5 mg with the conversion rate of 1805.6 μmol h−1 gcat-1), surpassing other photocatalysts so far.

Enhancing the Performance of a Metal-Free Self-Supported Carbon Felt-Based Supercapacitor with Facile Two-Step Electrochemical Activation.

Carbon felt (CF) is an inexpensive carbon-based material that is highly conductive and features extraordinary inherent surface area. Using such a metal-free, low-cost material for energy storage applications can benefit their practical implementation; however, only limited success has been achieved using metal-free CF for supercapacitor electrodes. This work thoroughly studies a cost-effective and simple method for activating metal-free self-supported carbon felt. As-received CF samples were first chemically modified with an acidic mixture, then put through a time optimization two-step electrochemical treatment in inorganic salts. The initial oxidative exfoliation process enhances the fiber’s surface area and ultimately introduced oxygen functional groups to the surface, whereas the subsequent reduction process substantially improved the conductivity. We achieved a 205-fold enhancement of capacitance over the as-received CF, with a maximum specific capacitance of 205 Fg−1, while using a charging current density of 23 mAg−1. Additionally, we obtained a remarkable capacitance retention of 78% upon increasing the charging current from 0.4 to 1 Ag−1. Finally, the cyclic stability reached 87% capacitance retention after 2500 cycles. These results demonstrate the potential utility of electrochemically activated CF electrodes in supercapacitor devices.

Interface engineering of nickel Hydroxide-Molybdenum diselenide nanosheet heterostructure arrays for efficient alkaline hydrogen production

The stacking of Molybdenum Diselenide (MoSe2) nanomaterials as well as its poor intrinsic conductivity lead to sluggish water dissociation kinetics, which limit the performance of the alkaline hydrogen evolution reaction (HER). Herein, we constructed Nickel Hydroxide Ni(OH)2-MoSe2 heterostructures directly on 3D self-supporting carbon cloth (CC) substrate via a simple hydrothermal and the subsequent chemical bath deposition process, then systemically studied the effect of the Ni(OH)2 deposition time on the HER performance. The synergistic effect between Ni(OH)2 and MoSe2 in the Ni(OH)2-MoSe2 heterostructures optimizes the poor conductivity and Gibbs free energy for water adsorption, thus improving the water dissociation kinetics and giving rise to fast electron transfer in the HER process. The Ni(OH)2-MoSe2/CC constructed in this way with a Ni(OH)2 deposition times of 30 min performs good catalytic activities with a low overpotential of 130 mV at -10 mA cm-2, a low Tafel slope of 78.2 mV dec-1 and good stability. Our results suggest that interface engineering combining with conductive substrate are conducive to enhance alkaline HER activity of MoSe2 and other similar transition metal dichalcogenides.

Application of Nanoparticles of Metal Organic Framework Zif-8 as Solute for Water Ultrafiltration Through Self-Supported Single-Walled Carbon Nanotube Buckypaper Membranes

Application of Nanoparticles of Metal Organic Framework Zif-8 as Solute for Water Ultrafiltration Through Self-Supported Single-Walled Carbon Nanotube Buckypaper Membranes

Rapid electron/ion transport in CNT/LiTi2(PO4)3@C–N electrodes for aqueous lithium-ion batteries with high stability, flexibility and safety

Self-supporting and flexible carbon nanotube/carbon-coated nitrogen-doped LiTi2(PO4)3 (CNT/LTP@C–N) hybrid films are manufactured via vacuum filtration and show high electrochemical properties.

Facile preparation of flexible porous carbon fibers as self-supporting sulfur cathode hosts for high-performance Li-S batteries.

Lithium-sulfur batteries are expected to be prospective candidates of high-energy-storage systems due to their high theoretical specific capacity. However, poor electrical conductivity, severe polysulfide shuttle effect and low sulfur utilization generally cause inferior electrochemical performance, hence hindering the practical development. In this study, common makeup cotton derived self-supporting porous carbon fibers (SPCFs) are prepared by a facile simultaneous activation/pyrolysis process accompanied by the effectively regulation of a KHCO3activator. The as-prepared SPCF materials have mutually cross-linked porous skeletons with an ultrahigh specific surface area of 2124.9 m2 g-1 and a large pore volume of 1.01 cm3 g-1, whilst exhibiting robust flexibility. When directly used as a self-supporting carbon current collector for encapsulating sulfur, the interconnected and abundant porous carbon fibers can not only immobilize soluble polysulfides, but also form a highly conductive network for the favorable redox transformation of adsorbed polysulfides. Moreover, the voids between the carbon skeletons can alleviate the volume change of sulfur cathodes during charge/discharge. Owing to these structure merits, the optimized SPCF-based sulfur cathode with a sulfur loading of 3.0 mg cm-2 shows a high coulombic efficiency of approximately 99% and delivers a first discharge capacity of 778 mA h g-1 at 0.2 C. Even at a relatively high current rate of 0.5 C, the reversible capacity of 450 mA h g-1 can be obtained after 300 cycles. The above-mentioned self-supporting porous carbon current collectors provide a guidance for high-performance lithium-sulfur batteries.

Self-Supporting Porous S-Doped Graphitic Carbon Nitride as a Multifunctional Support of AU Catalyst: Application to Highly Sensitive and Selective Determination of Arsenic (Iii) in a Wide Range of Ph

Self-Supporting Porous S-Doped Graphitic Carbon Nitride as a Multifunctional Support of AU Catalyst: Application to Highly Sensitive and Selective Determination of Arsenic (Iii) in a Wide Range of Ph

ZIF-67/wood derived self-supported carbon composites for electromagnetic interference shielding and sound and heat insulation

Co/C@WC composites showed better electromagnetic shielding performance and also exhibited sound insulation, temperature resistance and good mechanical performance.

Engineering of a self-supported carbon electrode with 2D ultrathin heterostructures of NiCo LDH/NiCoS via a MOF-template for sensitive detection of glucose and H2O2

A self-supported carbon electrode consisting of 2D ultrathin heterostructures of NiCo LDH/NiCoS exhibits superior performance for glucose and H2O2 sensing.

Hierarchical multi-channels conductive framework constructed with rGO modified natural biochar for high sulfur areal loading self-supporting cathode of lithium-sulfur batteries

The insulation of sulfur and Li2S/Li2S2 (discharge products) and the “shuttle” of soluble lithium polysulfides (LiPSs) seriously limit the research of high specific capacity lithium-sulfur (Li-S) batteries with high sulfur loading. Inspired by the natural architecture of pomelo peels, we report a self-supporting carbon framework (SCF) modified by reduced graphene oxide (rGO) as conductive skeleton and sulfur carrier for the cathode of rechargeable Li-S batteries. The high initial capacity (1489.65 mA h g−1) of SCF@rGO/S binder-free cathode with the high sulfur areal loading (∼5.50 mg cm−2) arise from the improved batteries conductivity by the interconnecting conductive skeleton. The SCF@rGO with hierarchical porous structure, abundant microchannels and oxygenic functional groups can effectively physical limit/intercept and chemical adsorption/anchor LiPSs, thereby improving the utilization of active sulfur and promoting the reuse. Sufficient active sites in SCF@rGO/S provide close electrical contact to accelerate electrons and ions transfer, resulting in high electrochemical activity and redox kinetics. Consequently, the SCF@rGO/S cathode exhibits an outstanding capacity retention (569.66 mA h g−1) and cycle stability at 1 C for over 200 long-term cycles with a decline of only 0.13% per cycle. Even at 2 C, the capacity is still up to 645.59 mA h g−1. The SCF@rGO/S cathode provide a feasible approach and strategy to develop high performance Li-S batteries.

In-situ generated NiCo2O4/CoP polyhedron with rich oxygen vacancies interpenetrating by P-doped carbon nanotubes for high performance supercapacitors

Supercapacitor with high storage capacity and small volumes are the development trends of miniaturization and portable energy storage systems. Herein, we design a novel self-supporting P-doped carbon nanotube (P-CNT) intercalating NiCo2O4/CoP core–shell polyhedron film. P-CNT is an ideal substrate with high electrical conductivity and interconnected porous architecture, which can enable the electrons transport to an external circuit from the electroactive component. NiCo2O4/CoP core–shell fluffy polyhedrons are derived from metal-organic frameworks with rich oxygen vacancies and abundant characteristics of pseudocapacitance, as well as better wettability. The self-supporting composite film readily achieves an ultra-high gravimetric and volumetric capacitance of 1918.4 F g−1 and 1074.3 F cm−3 at 1 A g−1. Accordingly, as-assembled hybrid supercapacitors using two binder-free electrodes, i.e., a self-supporting composite film as the positive electrode and P-doped CNT integrating graphene film as the negative electrode, harvest a remarkable gravimetric/volumetric energy density of 68.6 W h kg−1 (41.8 W h L−1) at 800 W kg−1 (488 W L−1). Our work suggests that the rational-designed NiCo2O4/CoP@P-CNTs electrode is a competitive candidate for designing next-generation supercapacitors with high volumetric energy density.

3D Self-Supported Nitrogen-Doped Carbon Nanofiber Electrodes Incorporated Co/CoOx Nanoparticles: Application to Dyes Degradation by Electro-Fenton-Based Process.

We developed free-standing nitrogen-doped carbon nanofiber (CNF) electrodes incorporating Co/CoOx nanoparticles (NPs) as a new cathode material for removing Acid Orange 7 (AO7; a dye for wool) from wastewater by the heterogeneous electro-Fenton reaction. We produced the free-standing N-doped CNF electrodes by electrospinning a polyacrylonitrile (PAN) and cobalt acetate solution followed by thermal carbonation of the cobalt acetate/PAN nanofibers under a nitrogen atmosphere. We then investigated electro-Fenton-based removal of AO7 from wastewater with the free-standing N-doped-CNFs-Co/CoOx electrodes, in the presence or not of Fe2+ ions as a co-catalyst. The electrochemical analysis showed the high stability of the prepared N-doped-CNF-Co/CoOx electrodes in electrochemical oxidation experiments with excellent degradation of AO7 (20 mM) at acidic to near neutral pH values (3 and 6). Electro-Fenton oxidation at 10 mA/cm2 direct current for 40 min using the N-doped-CNF-Co/CoOx electrodes loaded with 25 wt% of Co/CoOx NPs led to complete AO7 solution decolorization with total organic carbon (TOC) removal values of 92.4% at pH 3 and 93.3% at pH 6. The newly developed N-doped-CNF-Co/CoOx electrodes are an effective alternative technique for wastewater pre-treatment before the biological treatment.

Boron nanosheets induced microstructure and charge transfer tailoring in carbon nanofibrous mats towards highly efficient water splitting

Development of metal-free carbon-based electrocatalysts with high-efficiency and excellent durability towards both oxygen and hydrogen evolution reactions (OER and HER) in a single electrolyte system is crucial yet challenging for sustainable energy generation. In this work, we report a facile and scalable strategy for fabricating self-supporting boron carbon oxynitride nanofibrous (BCNONF) mats with controllable boron contents via electrospinning and subsequent thermal treatment. Notably, the optimal BCNONF mat affords outstanding OER performance in alkaline electrolyte with low overpotential of 403 mV at 10 mA·cm−2, small Tafel slop of 72.9 mV·dec−1, and high stability (88.1% current density retention after 10 h), outperforming the commercial Ir/C benchmark. Moreover, it can serve as a remarkable HER catalyst with better stability than that of the commercial Pt/C counterpart in the same electrolyte, indicating its bifunctional characteristics. When employed as both anode and cathode of an electrolyzer, the self-supporting BCNONF mats exhibit superior activities with a potential of only 1.79 V at 10 mA·cm−2 and high long-term durability (90.6% current density retention after 50 h) for overall water splitting. Furthermore, density functional theory (DFT) calculations reveal that the remarkable OER and HER bifunctional performance of the BCNONF catalyst are originated from the reduced adsorption strength of O atom and the stronger H* adsorption on the BCNO surface as compared to those on CNO surface, which in turn facilitate efficient interfacial charge transfer between the electrocatalytic intermediates and the BCNONF catalyst.

Structure-dependent electrochemical properties of cobalt (II) carbonate hydroxide nanocrystals in supercapacitors

In this work, we report the structure-dependent electrochemical performance of cobalt carbonate hydroxide (Co2(OH)2CO3) nanocrystals by experimental investigation and theoretical simulation. Different Co2(OH)2CO3 nanostructures including two-dimensional (2D) nanosheets (NSs) and one-dimensional (1D) nanowires (NWs), were synthesized on self-supported carbon cloth substrates by a facile hydrothermal method. Compared to 1D NWs, 2D Co2(OH)2CO3 NSs provided a short ion transfer path, and low electron transfer resistance during the electrochemical reaction. At the current density of 2 mA cm−2, 2D Co2(OH)2CO3 NSs exhibited a higher area capacitance of 2.15F cm−2 and better cycling performance (96.2% retention after 10,000 cycles) than that of 1D NWs (1.15F cm−2 and 90.1% retention). First-principles density functional theory (DFT) calculations revealed that the band gap of the (120) facet in 2D NSs was 0.2 eV, far less than of the (200) facet in 1D NWs (1.04 eV). Electrochemical impedance spectroscopy (EIS) measurements further indicated that the electron transfer and reaction kinetics were more efficient in 2D NSs. This work can provide an important insight in understanding the mechanism of electrochemical energy storage.

Self-supporting porous carbon nanofibers with opposite surface charges for high-performance inverted capacitive deionization

Capacitive deionization (CDI) has attracted much attention as a novel desalination technology. However, the oxidation of carbon anode and co-ion repulsion during charging are key issues which limit the CDI development. Inverted capacitive deionization (i-CDI) can attenuate these effects. Here, a simple method was presented to get the self-supporting carbon nanofibers electrodes with opposite surface charges to improve the deionization performance of i-CDI device. The electrospun polyacrylonitrile/polymethyl methacrylate (PAN/PMMA)-derived flexible carbon nanofiber was found to be negatively charged (N-CNF). The positively charged porous carbon nanofiber (P-CNF) was obtained by further heat treatment of N-CNF in the presence of ZnCl2. The P-CNF possesses much low negative potential of zero charge (PZC = −0.68 V), opposite to N-CNF (+0.32 V), measured by differential capacitance tests. With P-CNF as cathode and N-CNF as anode, the asymmetric capacitor device realized high performance i-CDI, and delivered a super high deionization capacity of 30.4 mg/g and very fast deionization rate (1.0 mg/g/min) with low specific energy consumption. The adsorption-desorption process in i-CDI was analyzed. The device exhibits superior cycling stability and regenerability over 70 cycles. These flexible carbon nanofibers with substantial surface charge difference render it favorable for i-CDI application.

Conductive metal-organic frameworks promoting polysulfides transformation in lithium-sulfur batteries

Metal organic frameworks (MOFs) have been extensively investigated in Li-S batteries owing to high surface area, adjustable structures and abundant catalytic sites. Nevertheless, the insulating nature of traditional MOFs render retarded kinetics of polysulfides conversion, leading to insufficient utilization of sulfur. In comparison, conductive MOFs (c-MOFs) show great potential for promoting polysulfides transformation due to superb electronic conductivity. In this work, a nickel-catecholates based c-MOF, Ni-HHTP (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene), is designed to regulate surface chemistry of self-supported carbon paper for advanced Li-S batteries. Taking advantage of the porous structure and high conductivity, the as-prepared Ni-HHTP is conducive to synergising strengthening the chemisorption of polysulfides and accelerating the reaction kinetics in Li-S batteries, significantly mitigating the polysulfides diffusion from the non-encapsulated sulfur cathode, therefore promoting polysulfides transformation in Li-S batteries. This work points out a promising modification strategy for developing advanced sulfur cathode in Li-S batteries.

In situ construction of multi-dimensional Co3O4/NiCo2O4 hierarchical flakes on self-supporting carbon substrate with ultra-high capacitance for hybrid supercapacitors

Research on environmentally friendly energy storage devices is an important strategy to solve the energy crisis and environmental pollution. Herein, a novel self-supporting electrode based on multi-dimensional Co3O4/NiCo2O4 hierarchical flakes coating on graphene/carbon sphere (rGO/CS) conductive substrate is reasonably designed. Firstly, a simple hydrothermal method is used to synthesize NiCo2O4 with both flake and nanoneedle morphology on the rGO/CS substrate. Subsequently, Co3O4/NiCo2O4@rGO/CS is obtained by in-situ growth of metal organic frameworks polyhedrons on the surface of NiCo2O4 flakes followed by calcination. In the unique structure, benefitting from the synergy between the substrate and multi-element transition metal oxides, the integrated film shows good conductivity, high specific surface area and abundant active sites. Thus, the binder-free electrode exhibits an ultra-high specific capacitance of 3876.6 F g−1 (538.4 mA h g−1) at 1 A g−1. A hybrid supercapacitor is assembled with activated carbon as the negative electrode and Co3O4/NiCo2O4@rGO/CS as the positive electrode, the device shows a highest energy density of 56.5 Wh kg−1 at a power density of 800 W kg−1. After 6000 charge–discharge cycles, 92.5% of the initial capacitance can be still maintained, indicating its good application prospects in energy storage materials.

Engineering of yolk-shelled FeSe2@nitrogen-doped carbon as advanced cathode for potassium-ion batteries

Potassium-ion batteries (KIBs) have become the most promising alternative to lithium-ion batteries for large-scale energy storage system due to their abundance and low cost. However, previous reports focused on the intercalation-type cathode materials usually showed an inferior capacity, together with a poor cyclic life caused by the repetitive intercalation of large-size K-ions, which hinders their practical application. Here, we combine the strategies of carbon coating, template etching and hydrothermal selenization to prepare yolk-shelled FeSe2@N-doped carbon nanoboxes (FeSe2@C NBs), where the inner highly-crystalline FeSe2 clusters are completely surrounded by the self-supported carbon shell. The integrated and highly conductive carbon shell not only provides a fast electron/ion diffusion channel, but also prevents the agglomeration of FeSe2 clusters. When evaluated as a conversion-type cathode material for KIBs, the FeSe2@C NBs electrode delivers a relatively high specific capacity of 257 mAh/g at 100 mA/g and potential platform of about 1.6 V, which endow a high energy density of about 411 Wh/kg. Most importantly, by designing a robust host with large internal void space to accommodate the volumetric variation of the inner FeSe2 clusters, the battery based on FeSe2@C NBs exhibits ultra-long cycle stability. Specifically, even after 700 cycles at 100 mA/g, a capacity of 221 mAh/g along with an average fading rate of only 0.02% can be retained, which achieves the optimal balance of high specific capacity and long-cycle stability.

Porous Fe-Co-P nanowire arrays through alkaline etching as self-supported electrodes for efficient hydrogen production

In the present work, an efficient four-step strategy to fabricate the Fe-Co-P porous nanowire arrays in situ grown on a self-supported carbon cloth (denoted as Fe-Co-P/CC) for developing excellent HER activity is reported. The four steps include the preparation of the CoFeZn-precursor by a hydrothermal reaction, the formation of pore-forming agent (ZnO) after annealing treatment, the alkaline etching of ZnO, and phosphorization. Particularly, the alkaline-etched porous Fe-Co-P nanowire-arrays contribute to enhancing the catalytic activity by the exposure of more electrochemical active sites. The as-prepared Fe-Co-P/CC which was prepared by the rational Co-Fe molar ratio, as a binder-free electrocatalyst, shows a high-performance HER with a small overpotential of 121 mV in 1 M KOH and 124 mV in 0.5 M H2SO4 at a current density of 10 mA·cm−2, as well as a good Tafel slope value of 118 mV/dec and 85 mV/dec in alkaline and acid media, respectively, owing to the well-optimized pore-structures and active sites. Additionally, the catalyst almost maintains its electrochemical activity for about 24 and 16 h under alkaline and acidic conditions, respectively. This work provides a new idea for the synthesis of high-efficiency, binder-free electrodes for high-purity hydrogen production.

Heterogeneous electro-Fenton catalysis with self-supporting CFP@MnO2-Fe3O4/C cathode for shale gas fracturing flowback wastewater

Self-supporting electrodes have triggered great interests in improving electro-Fenton (EF) system for degradation of refractory organic pollutants. In this work, a novel self-supporting carbon fiber paper (CFP) electrode modified by transition metals, e.g. Fe and Mn, was fabricated and employed as a heterogeneous EF cathode. The prepared electrode exhibited excellent degradation for a number of typical organic pollutants along with superior stability. Remarkably, a high removal efficiency was achieved in the EF treatment of shale gas fracturing flowback wastewater. Results indicated that 65.2% TOC and 74.8% COD were eliminated after 4 h degradation. The residual COD value of the real wastewater was 80 mg L−1, meeting the emission requirement of the integrated wastewater discharge standard (COD＜100 mg L−1) with a low specific energy consumption of 6.9kWhkg−1COD−1. This work demonstrates a competing alternative for efficient decontamination of real wastewater using an electro-Fenton strategy with a low-cost electrode.