Surface Of Carbon Nanofibers Research Articles

Synthesis of Needle-like CoO Nanowires Decorated with Electrospun Carbon Nanofibers for High-Performance Flexible Supercapacitors

Needle-like CoO nanowires have been successfully synthesized by a facile hydrothermal process on an electrospun carbon nanofibers substrate. The as-prepared sample mesoporous CoO nanowires aligned vertically on the surface of carbon nanofibers and cross-linked with each other, producing loosely porous nanostructures. These hybrid composite electrodes exhibit a high specific capacitance of 1068.3 F g−1 at a scan rate of 5 mV s−1 and a good rate capability of 613.7 F g−1 at a scan rate of 60 mV s−1 in a three-electrode cell. The CoO NWs@CNF//CNT@CNF asymmetric device exhibits remarkable cycling stability and delivers a capacitance of 79.3 F/g with a capacitance retention of 92.1 % after 10,000 cycles. The asymmetric device delivers a high energy density of 37 Wh kg−1 with a power density of 0.8 kW kg−1 and a high power density of 16 kW kg−1 with an energy density of 23 Wh kg−1. This study demonstrated a promising strategy to enhance the electrochemical performance of flexible supercapacitors.

High-performance biomass tar-based nanofibers with CoNi nanosheets prepared by electrospinning for supercapacitor electrode material

Biomass-based nanofibers prepared by electrospinning have broad prospects in the field of supercapacitors. In this work, biomass tar-based carbon nanofibers (CNFs) are prepared by electrospinning technology, and the CoNi nanosheets are grown on the surface of CNFs. The obtained electrode materials have a three-dimensional open petal-like nanofiber structure, and the results of the electrochemical performances show that the CoNi@CNF-1 has a specific capacitance of 474.4F g−1 at 0.5 A g−1, an energy density of 65.9 Wh kg−1 and a power density of 250 W kg−1. After 5000 charge-discharge cycles, the CoNi@CNF-1 still maintains 95.4 % of its original capacitance in the three-electrode system. This work provides an important reference for the effective treatment of biomass tar and its application in the field of electrochemical energy storage.

Enhancing electrochemical properties of bacterial cellulose-derived carbon nanofibers through physical CO2 activation

Carbon nanofiber (CNF) derived from carbonization of bacterial cellulose (BC), with a unique three-dimensional porous nanostructure, has received significant interest in electrochemical applications. In this study, CNF samples were physically activated in CO2 at different temperatures and durations. Raman spectroscopy and FTIR analysis showed that CO2 activation caused hexagonal lattice defects, disorder, and oxygen-related functional groups in an amorphous carbon structure. CNF surface morphology changed after physical activation, reducing fiber diameter to 55 nm and introducing mesopores. Through activation temperature and time adjustments, surface area (870.1 m2/g) and micropore surface area (535.6 m2/g) and pore volume (0.2148 cm3/g) increased. EDX elemental analysis showed that activated CNF had a carbon concentration of > 90 %, while XPS analysis showed surface functional groups like C-C (sp2) and C-C (sp3) hybridization, which could improve electrolyte ion adsorption and accessibility. Electrochemical properties improved owing to CO2 activation. The optimal activation condition of 800 ℃ for 60 min resulted in the highest specific area capacitance of 552 mF cm−2 at 1 mA cm−2. This activated CNF electrode retained capacitance nearly unchanged up to 3,000 cycles. It also achieved the highest energy density of 76.7 mWh cm−2 at 500 mW cm−2. This study demonstrates the efficacy of CO2 physical activation for enhancing the electrochemical properties of CNF electrodes. The findings also highlight the importance of tailoring activation conditions, providing valuable insights for the design of advanced energy storage materials.

Nano-etching of carbon nanofiber surface and subsequent Fe–N–C thin film coating for enhancement of oxygen evolution reaction

The oxygen evolution reaction (OER) is involved in many electrical–chemical energy conversion systems; however, the slow reaction rate of the OER leads to a high overpotential (η) and low energy efficiency. Recently, an extremely low-η OER phenomenon was observed at a carbonaceous Fe–N-doped thin film with enriched step edges on highly oriented pyrolytic graphite and the carbon fiber surface in an alkaline electrolyte, although the activity was limited. In this study, multi-walled carbon nanotubes (MWCNTs) were used as substrates to utilize their high specific surface areas to develop an active OER catalyst. Nanoscale etching of the MWCNT surface was performed by Fe3O4 nanoparticle loading and subsequent heat treatment in an inert atmosphere, followed by acid washing. Afterwards, a carbonaceous thin film containing Fe and N was coated on the surface via sublimation, deposition, and pyrolysis of Fe phthalocyanine (Pc). A roughened surface was observed for the FePc-derived thin film coated on the nano-etched MWCNT, in contrast to the smooth surface observed for the film coated on the MWCNT without nano-etching. The combination of the nano-etching and the thin-film coating enhanced the OER, which was analyzed by parallel Tafel processes.

Porous carbon nanofiber/porphyrin-based metal organic frameworks/TiO2 nanoparticles ternary materials for selective detection and photoreduction of Cr(Ⅵ)

For the heavy metal ion Cr(Ⅵ), which is widely present in wastewater with acute toxicity, mutagenicity and carcinogenicity, we successfully constructed a ternary material of PCNFs/CuMOF/TiO2 for rapid detection and photoreduction of Cr(Ⅵ). The material has obvious advantages: on the one hand, ZIF-8/polyacrylonitrile (PAN) nanofibers and their derived porous carbon nanofibers (PCNFs) were synthesized by electrospinning and high temperature carbonization, which provided a loading platform for CuMOF and TiO2, effectively inhibited the agglomeration of CuMOF and TiO2, and ensured the exposure of active sites. Meanwhile, its excellent conductivity can promote the effective migration of photogenerated carriers in the photocatalytic process. On the other hand, CuMOF constructed with tetra-carboxyphenylporphyrin (TCPP) as the linking arm and Cu(NO3)2·3 H2O as the metal node was directly loaded on the surface of porous carbon nanofibers (PCNFs), and then TiO2 nanoparticles were introduced by hydrothermal method. CuMOF ensures the responsiveness of the composite to visible light. Moreover, the energy level structure of TiO2 matches with CuMOF, which effectively inhibits the recombination of photogenerated electron-hole pairs (e--h+). The results show that the colorimetric detection of Cr(Ⅵ) was achieved by using 3,3′,5,5′-tetramethylbenzidine (TMB) as the sensing probe. The method was highly selective for Cr(Ⅵ) ions with a limit of detection (LOD) of 24.1 nM. Encouragingly, PCNFs/CuMOF/TiO2 was further used as a photocatalyst. The reduction rate of Cr(Ⅵ) under visible light irradiation is 96.1 % in 60 min. The active species trapping experiments confirm the key role of e- photocatalytic reduction, upon which a possible photocatalytic mechanism is proposed. The degradation rate of Cr(Ⅵ) is still 86.4 % after the five times cycle, and the good stability and reproducibility allow it to be used as a potential green photocatalyst for the conversion of Cr(Ⅵ) to Cr(Ⅲ).

Unique Self-Phosphorylating Polybenzimidazole of the 6F Family for HT-PEM Fuel Cell Application.

High-temperature polymer-electrolyte membrane fuel cells (HT-PEMFCs) are a very important type of fuel cells since they operate at 150-200 °C, making it possible to use hydrogen contaminated with CO. However, the need to improve the stability and other properties of gas-diffusion electrodes still impedes their distribution. Self-supporting anodes based on carbon nanofibers (CNF) are prepared using the electrospinning method from a polyacrylonitrile solution containing zirconium salt, followed by pyrolysis. After the deposition of Pt nanoparticles on the CNF surface, the composite anodes are obtained. A new self-phosphorylating polybenzimidazole of the 6F family is applied to the Pt/CNF surface to improve the triple-phase boundary, gas transport, and proton conductivity of the anode. This polymer coating ensures a continuous interface between the anode and proton-conducting membrane. The polymer is investigated using CO2 adsorption, TGA, DTA, FTIR, GPC, and gas permeability measurements. The anodes are studied using SEM, HAADF STEM, and CV. The operation of the membrane-electrode assembly in the H2/air HT-PEMFC shows that the application of the new PBI of the 6F family with good gas permeability as a coating for the CNF anodes results in an enhancement of HT-PEMFC performance, reaching 500 mW/cm2 at 1.3 A/cm2 (at 180 °C), compared with the previously studied PBI-O-PhT-P polymer.

Application of functionalized carbon nanofibers as a modifying additive to motor oil

Due to the widespread of lubricants, improving their tribological characteristics remains an important practical task. Among the promising modifying additives, carbon nanomaterials attract special attention. Such materials are found to improve the antifriction characteristics of lubricants and oils. In the present research, carbon nanofibers were synthesized via catalytic pyrolysis of a mixture of light hydrocarbons (C2-C4) over the NiCu catalyst. In order to form functional groups on the surface of carbon nanofibers, they were treated with diluted acids HCl, HNO3, and H2SO4 as well as with concentrated HNO3. The functionalized samples were comprehensively characterized by a set of physicochemical methods including atomic absorption spectroscopy, scanning and transmission electron microscopies, low-temperature nitrogen adsorption, X-ray photoelectron spectroscopy, temperature-programmed desorption/oxidation, and Raman spectroscopy. As defined, the surface oxygen concentration in the samples varies from 3.5 to 16.3 at.%. It was shown that the addition of modified carbon nanofibers to a motor oil leads to an improvement in its tribological characteristics. In particular, the most effective additive was the sample treated with diluted HNO3. The motor oil with this modifying additive exhibited the heating temperature decreased by 10 °C and the contact spot area on the stationary body decreased by 20 %.

Boosting Oxygen Reduction Reaction Selectivity in Metal Nanoparticles with Polyoxometalates.

The lack of selectivity toward the oxygen reduction reaction (ORR) in metal nanoparticles can be linked to the generation of intermediates. This constitutes a crucial constraint on the performance of specific electrochemical devices, such as fuel cells and metal-air batteries. To boost selectivity of metal nanoparticles, a novel methodology that harnesses the unique electrocatalytic properties of polyoxometalates (POM) to scavenge undesired intermediates of the ORR (such as HO2 -) promoting selectivity is proposed. It involves the covalent functionalization of metal nanoparticle's surface with an electrochemically active capping layer containing a new sulfur-functionalized vanadium-based POM (AuNP@POM). To demonstrate this approach, preformed thiolate Au(111) nanoparticles with a relatively poor ORR selectivity are chosen. The dispersion of AuNP@POM on the surface of carbon nanofibers (CNF) enhances oxygen diffusion, and therefore the ORR activity. The resulting electrocatalyst (AuNP@POM/CNF) exhibits superior stability against impurities like methanol and a higher pH tolerance range compared to the standard commercial Pt/C. The work demonstrates for the first time, the use of a POM-based electrochemically active capping layer to switch on the selectivity of poorly selective gold nanoparticles, offering a promising avenue for the preparation of electrocatalyst materials with improved selectivity, performance, and stability for ORR-based devices.

Progressive deposition on carbon nanofiber films enables dendrite-free zinc plating

Zinc anodes tend to form irregular and non-planar electrodeposits during repeated cycles, leading to the dendrite growth and consequently resulting in internal short circuits of Zn-based batteries and security problems. A progressive deposition is investigated in the present study by introducing oxygen functional groups and macropores into the carbon nanofiber film to regulate the nucleation and growth of Zn. Experimental analyses and theoretical simulation show that zincophilic oxygen functional groups act as preferred deposition sites with ultralow Zn nucleation overpotential to guide the initial nucleation of Zn on the whole surface of carbon nanofibers. The macropores with higher Zn2+ concentration and current density serve as the preferred paths for the subsequent growth of Zn inside. Deposited Zn will progressively fill the internal void space of the entire carbon nanofiber film. The carbon nanofiber film with the progressive deposition enables dendrite-free Zn plating/stripping. Symmetric cells with OPCNF-Zn electrodes exhibit a long cycle life over 1300 h at 1 mA cm−2 for 1 mA h cm−2.

Spinning of Carbon Nanofiber/Ni–Cu–S Composite Nanofibers for Supercapacitor Negative Electrodes

The preparation of composite carbon nanomaterials is one of the methods for improving the electrochemical performance of carbon-based electrode materials for supercapacitors. However, traditional preparation methods are complicated and time-consuming, and the binder also leads to an increase in impedance and a decrease in specific capacitance. Therefore, in this work, we reduced Ni-Cu nanoparticles on the surface of nitrogen-doped carbon nanofibers (CNFs) by employing an electrostatic spinning method combined with pre-oxidation and annealing treatments. At the same time, Ni-Cu nanoparticles were vulcanized to Ni–Cu–S nanoparticles without destroying the structure of the CNFs. The area-specific capacitance of the CNFs/Ni–Cu–S–300 electrode reaches 1208 mF cm−2 at a current density of 1 mA cm−2, and the electrode has a good cycling stability with a capacitance retention rate of 76.5% after 5000 cycles. As a self-supporting electrode, this electrode can avoid the problem of the poor adhesion of electrode materials and the low utilization of active materials due to the inactivity of the binder and conductive agent in conventional collector electrodes, so it has excellent potential for application.

Effect of etchant gases on the structure and properties of carbon nanofibers

The utilization of plasma-enhanced chemical vapor deposition (PECVD) for carbon nanofiber (CNF) growth using NH3 as the etchant gas has been extensively documented. Notably, NH3 serves a dual role by etching excess carbon and providing N heteroatoms. Most studies neglect to address this phenomenon, despite the well-known impact of N-doping on CNF properties. Furthermore, NH3 exhibits specific interactions with C2H2—it not only etches excess carbon, but also suppresses the dissociation of C2H2. The implications of this phenomenon on CNF micro- and macroscale morphology have not been comprehensively investigated. To elucidate the influence of etchant gases on CNF structure and properties, we fabricated two types of CNFs - N-doped CNFs (N-CNF) and undoped CNFs (U-CNF). Both were grown on identical substrates using the same carbon source (C2H2) but different etchants (NH3 and H2). Their microstructure and surface chemistry were analyzed using transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). Electrochemical properties were investigated using cyclic voltammetry (CV). U-CNFs were found to have a larger population density and a more disordered structure than N-CNFs. N-doping was confirmed in N-CNFs using XPS analysis, which also revealed differences in relative amounts of sp2 C and O functional groups. U-CNFs exhibited distinct electrochemical properties, including smaller pseudocapacitance, larger potential window, slower outer sphere redox (OSR) kinetics, and diminished dopamine sensitivity. Electrochemical differences were rationalized based on CNF structure and surface chemistry, which, in turn, were attributed to how different etchant gases influence the PECVD process.

Preparation of Zeolitic Imidazolate Framework and Carbon Nanofiber Composites for Nitrofurazone Detection

Metal–organic frame (MOF) materials may have the advantages of a regular pore structure, large porosity, and large specific surface area, which could provide better catalytic activity, but they have some disadvantages in electrocatalysis. In contrast, carbon nanofibers (CNFs) prepared by electrospinning methods have good conductivity and stability. Therefore, this research aimed to generate MOF/CNFs composite materials to improve the electrochemical properties of MOF materials and apply them to the field of electrochemical sensing. This experiment was based on the preparation of straight unidirectional CNFs by an electrospinning method at 2000 RPM. The original method of preparing zeolitic imidazolate frameworks (ZIF-8) was improved and ZIF-8 was uniformly dispersed on the surface of CNFs to form a ZIF-8/CNF composite with a fiber diameter of about 0.10 to 0.35 µm. The specific surface area of the CNFs was about 42.28 m2/g, while that of the ZIF-8/CNF composite was about 999.82 m2/g. The specific surface area of the ZIF-8/CNF composite was significantly larger than that of CNFs. The GCE/ZIF-8/CNF electrode had an excellent electrochemical reaction, with an oxidation peak at about 216 μA, which proved that the ZIF-8/CNF composite material would have good catalytic activity and excellent electrochemical properties for the detection of nitrofurazone compared to other modified electrodes.

Preparation and characterization of palladium nanoparticle-embedded carbon nanofiber membranes via electrospinning and carbonization strategy.

Carbon nanofiber membranes (CNMs) are expected to be used in many energy devices to improve the reaction rate. In this paper, CNMs embedded with palladium nanoparticles (Pd-CNMs) were prepared by electrospinning and carbonization using polyimide as the raw material. The effects of carbonization temperature, carbonization atmosphere, and heating rate on the physicochemical properties of the as-obtained Pd-CNMs were studied in detail. On this basis, the electrocatalytic performance of Pd-CNMs prepared under optimal conditions was characterized. The results showed that highly active zero-valent palladium nanoparticles with uniform particle size could be distributed on the surface of carbon nanofibers. Under vacuum conditions, at a carbonization temperature of 800 °C and a heating rate of 2 °C min-1, Pd-CNMs have lower H2O2 yield, lower Tafel slope (73.3 mV dec-1), higher electron transfer number (∼4), and superior durability, suggesting that Pd-CNMs exhibit excellent electrocatalytic activity for ORR in alkaline electrolyte. Therefore, polyimide-derived CNMs embedded with Pd nanoparticles are expected to become an excellent cathode catalyst layer for fuel cells.

Universal architecture and defect engineering dual strategy for hierarchical antimony phosphate composite toward fast and durable sodium storage

Antimony (Sb)-based anode materials are feasible candidates for sodium-ion batteries (SIBs) due to their high theoretical specific capacity and excellent electrical conductivity. However, they still suffer from volume distortion, structural collapse, and ionic conduction interruption upon cycling. Herein, a hierarchical array-like nanofiber structure was designed to address these limitations by combining architecture engineering and anion tuning strategy, in which SbPO4−x with oxygen vacancy nanosheet arrays are anchored on the surface of interwoven carbon nanofibers (SbPO4−x@CNFs). In particular, bulky PO43− anions mitigate the large volume distortion and generate Na3PO4 with high ionic conductivity, collectively improving cyclic stability and ionic transport efficiency. The abundant oxygen vacancies substantially boost the intrinsic electronic conductivity of SbPO4, further accelerating the reaction dynamics. In addition, hierarchical fibrous structures provide abundant active sites, construct efficient conducting networks, and enhance the electron/ion transport capacity. Benefiting from the advanced structural design, the SbPO4−x@CNFs electrodes exhibit outstanding cycling stability (1000 cycles at 1.0 A g−1 with capacity decay of 0.05% per cycle) and rapid sodium storage performance (293.8 mA h g−1 at 5.0 A g−1). Importantly, systematic in-/ex-situ techniques have revealed the “multi-step conversion-alloying” reaction process and the “battery-capacitor dual-mode” sodium-storage mechanism. This work provides valuable insights into the design of anode materials for advanced SIBs with elevated stability and superior rate performance.

Synergism of Edge Effect and Interlayer Engineering of VS2 on CNFs for Rapid and Precise NO2 Detection.

Although two-dimensional (2D) transition-metal dichalcogenides (TMDs) exhibit attractive prospects for gas-sensing applications, the rapid and precise sensing of TMDs at low loss remains challenging. Herein, a NO2 sensor based on an expanded VS2 (VS2-E)/carbon nanofibers (CNFs) composite (abbreviated as VS2-E-C) with ultrafast response/recovery at a low-loss state is reported. In particular, the impact of the CNF content on the NO2-sensing performance of VS2-E-C was thoroughly explored. Expanded VS2 nanosheets were grafted onto the surface of hollow CNFs, and the combination boosted the charge transport, exposing abundant active edges of VS2, which enhanced the adsorption of NO2 efficiently. The activity of the VS2 edge is further confirmed by stronger NO2 adsorption with a more negative adsorption energy (-3.42 eV) and greater than the basal VS2 surface (-1.26 eV). Moreover, the exposure of rich edges induced the emergence of the expanded interlayers, which promoted the adsorption/desorption of NO2 and the interaction of gas molecules within VS2-E-C. The synergism of edge effect and interlayer engineering confers the VS2-E-C3 sensor with ultrafast response/recovery speed (9/10 s) at 60 °C, high sensitivity (∼2.50 to 15 ppm NO2), good selectivity/stability, and a low detection limit of 23 ppb. The excellent "4S" functions indicate the promising prospect of the VS2-E-C3 sensor for fast and precise NO2 detection at low-loss condition.

Fabrication of Activated Multiporous Carbon Nanofibers Using Vacuum Plasma for High-Capacity Energy Storage

Porous carbon nanofibers are widely used as supercapacitor electrode materials due to their excellent physical adsorption/desorption operation and smooth transport of ions. The acid/base activation method is commonly used to generate micropores on the surface of carbon nanofibers, but controlling the activation level and minimizing the release of harmful chemicals pose challenges. This study proposed a method for producing activated multiporous carbon nanofibers that is easier to operate and more environmentally friendly. It utilizes the vacuum plasma process to enhance surface area and introduce functional groups onto the electrospun polymer nanofibers. Subsequent heat treatment results in the formation of activated multiporous carbon nanofibers. The type and density of the functional group introduced into the carbon structure were adjusted to the type of plasma gas (O2, NH3 and C4F8) being exposed. Among them, oxygen plasma-treated carbon nanofibers (O-MPCNFs) not only have a much larger active surface (517.84 m2 g−1) than other gases (290.62 m2 g−1 for NH3 and 159.29 m2 g−1 for C4F8), but also generate a lot of micropores, promoting rapid adsorption/desorption-inducted charges; therefore, they have excellent energy storage capacity. The O-MPCNF-based symmetrical two-electrode supercapacitor has a high specific capacitance (173.28 F g−1), rate capability and cycle stability (94.57% after 5000 cycles).

Eliminating bandgap between Cu-CeO2-x heterointerface enabling fast electron transfer and redox reaction in Li-S batteries

The design of catalyst systems with reasonable configuration to alleviate the shuttle effects and strength conversion kinetics of polysulfide (LiPSs) in lithium-sulfur (Li-S) batteries still remains a challenge. Herein, a novel Cu-CeO2-x heterointerface is constructed by an ion migrating-capturing process. The Cu2+dispersed inner the carbon nanofibers (CNF) is controlled released and transferred outside gradually, and finally is captured by the CeO2 nanoparticles anchored on the CNF surface and form a Cu-CeO2-x heterointerface. Synergistically, the CeO2 capture and disperse Cu clusters as a hosting material, while the Cu decoration prevent further aggregation of CeO2 at harsh reaction conditions. Thus, the orbital interaction between CeO2 and Cu induce numerous oxygen vacancy and band gap disappearance at the heterointerface, resulting in a lower energy barrier of electron/hole separation and fast electron transfer in the metallic Cu-CeO2-x composites. Eventually, the Cu-CeO2-x can accelerate the catalytic conversion of LiPSs and decomposition of Li2S, and the Li-S cell deliver an excellent performance of 626 mA h g−1 after 800 cycles at a current density of 2 C, with a decay rate of only 0.046 % per cycle. This work reveals the formation mechanism of oxygen vacancy and disappearance of band gap at heterointerface, opening up a new prospect for rational design of various heterogeneous structures for cathode materials.

Configurations Manipulation of Electrospun Membranes Based on High‐Entropy Alloys–Enabled High‐Performance Solar Water Evaporation

Solar‐driven interfacial steam technology converts photons into heat energy directly and therefore realizes the effective removal of environmental pollutants, which presents huge potential in seawater desalination and freshwater production. To realize efficient and rapid solar‐driven water evaporation, developing and designing efficient photothermal conversion materials is of great significance. Herein, a high‐entropy alloy (HEA) fiber membrane with rapid heating and wide spectral response is synthesized via adjusting high‐entropy metals diffusion on the surface of carbon nanofibers by an electrospinning technology. Benefiting from the low equivalent evaporation enthalpy and high solar spectrum capacity of HEA fibers, the HEA (FeCoNiCuMn)‐carbon nanofiber‐5S2 achieves a rapid steam‐generation rate of 2.74 kg m−2 h−1 with a solar‐to‐vapor conversion efficiency of 99.4% under 1 sun illumination. In addition, the evaporator presented a stable seawater desalination and wastewater purification performance. Therefore, the HEA‐based solar evaporator can be an alternative photothermal material for efficient solar steam generation.

Design of p-CuS/n-CdFe2O4 heterojunction passivated with carbon nanofiber (CNF) for impressive performance in supercapacitor and photoelectrochemical water splitting

One of the most crucial strategies toward creating a greener future by minimizing fossil fuel use is the development of novel nanostructures with enhanced energy storage and energy conversion capacities. In this study, p-type copper sulfide (CuS)–n-type cadmium ferrite (CdFe2O4) heterojunction nanostructures were synthesized and passivated with a carbon nanofiber (CNF) to form a surface charge mediator, resulting in a novel material denoted as CuS–CdFe2O4/CNF. The developed hybrid heterojunction composite demonstrated a specific capacitance of 640 F g−1 at a current density of 0.5 A g−1 and photocurrent density of − 602 μA cm−2 (vs. Ag/AgCl) in the supercapacitor and photoelectrochemical (PEC) water splitting applications, respectively. In supercapacitors, these composites exhibited specific capacitances that were 2.0, 3.2, 1.6, 2.7, and 1.2 times higher than those of the pristine (CuS, CdFe2O4) and binary (CuS/CNF, CdFe2O4/CNF, and CuS–CdFe2O4) components, respectively. The CuS-CdFe2O4/CNF composite exhibited significant cycle stability (84%) even after 5000 cycles. It also demonstrated a photocurrent response of over 50% in PEC water splitting under light illumination compared with that under dark conditions. The creation of a heterojunction interface, which results from the semiconductor properties of p- and n-type materials connected to the CNF surface, is responsible for the outstanding performance of the composite. To develop a specialized charge-transport pathway that produces highly reactive sites, allows quick electron accessibility, reduces RCT, and encourages strong ion diffusion, we added material components to our design. Thus, we expanded the possible applications of current materials in energy-related industries, and dependence on the inherent qualities of materials was decreased.

Effect of Cu on Performance of Self-Dispersing Ni-Catalyst in Production of Carbon Nanofibers from Ethylene

The development of effective catalysts for the pyrolysis of light hydrocarbons with the production of carbon nanomaterials represents a relevant direction. In the present work, the influence of copper addition on performance of a self-dispersed Ni-catalyst and structural features of the obtained carbon nanofibers (CNFs) was studied. The precursors of Ni and Ni-Cu catalysts were prepared by activation of metal powders in a planetary mill. During contact with the C2H4/H2 reaction mixture, a rapid disintegration of the catalysts with the formation of active particles catalyzing the growth of CNFs has occurred. The kinetics of CNF accumulation during ethylene decomposition on Ni- and Ni-Cu catalysts was studied. The effect of temperature on catalytic performance was explored and it was shown that introduction of copper promotes 1.5–2-fold increase in CNFs yield in the range of 525–600 °C; the maximum CNFs yield (100 g/gcat and above, for 30-min reaction) is reached on Ni-Cu-catalyst at 575–600 °C. A comparative analysis of the morphology and structure of CNF was carried out using electron microscopy methods. The growth mechanism of carbon filaments in the shape of “railway crossties” on large nickel crystals (d > 250 nm) was proposed. It was found that the addition of copper leads to a decrease in the bulk density of the carbon product from 40–60 to 25–30 g/L (at T = 550–600 °C). According to the low-temperature nitrogen adsorption data, specific surface area (SSA) of CNF samples (at T < 600 °C) lies in the range of 110–140 m2/g, regardless of the catalyst composition; at T = 600 °C the introduction of copper contributed to an increase in the specific surface of CNF by 100 m2/g.