Search

Covalent organic frameworks (COFs) possess extraordinary porosity, structural diversity, and good electrochemical performance, and have broad application prospects in the field of energy storage. However, the low conductivity of COFs limits its further development. In this paper, the electrochemical performance of triphenylamine-based COFs (TPA-COFs) was improved by compounding with highly conductive polyaniline (PANI) using solvothermal synthesis process. The highly conductive polyaniline fibers can act as conductive path in the composite to accelerate the charge transfer rate of TPA-COFs. The π-π interaction between TPA-COFs and PANI effectively decreases the agglomeration degree of PANI. The good dispersion of composite results in that the specific surface area of TPA-COFs/PANI-20 is high as 1233.9 m2 g−1, which provides rich diffusion channels for electrolyte ions. Moreover, the strong π-π structure in the composites ensures the stability of the material skeleton. Thus, TPA-COFs/PANI composite exhibits excellent rate characteristics and cycling stability.

This paper demonstrated that the hues of both neutral and oxidised colours of isoindigo-based donor–acceptor polymers could be tuned subtly by means of variation of the number and type of donor groups.

PtCu alloy supported on acid-treated multi-walled carbon nanotube (PtCu/MWCNT) catalysts were prepared through polyol reduction method. The prepared PtCu/MWCNT composites were annealed at different temperatures to study the effects of annealing temperatures on the particle size, structure, surface morphology, and the activity and stability of methanol oxidation reaction (MOR). X-ray diffraction (XRD), transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS) were used to study the structure and physical characteristics of the catalyst. These physical characterization analyses all confirmed the formation of PtCu alloy, and the particle size of the catalysts rose with the increase of annealing temperature. The activity and stability of catalysts were further measured by cyclic voltammetry (CV) and accelerated durability tests (ADTs), respectively. It was found after annealing at 400℃ that the PtCu/MWCNT catalyst has higher activity and longer durability toward MOR. This work demonstrated that PtCu catalysts after annealing in a H2 atmosphere will cause a change in the surface atomic configuration and degree of alloying of PtCu catalysts, which determines the activity and long-term durability of PtCu/MWCNT catalyst.

In this work, Ru-doped Ta2O5 was firstly synthesized as support for Pt nanoparticles by calcination and chemical precipitation. The prepared Pt/Ru-Ta2O5 catalysts were characterized by transmission electron microscope (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). These characterization methods confirm that Pt nanoparticles were successfully supported on Ru-doped Ta2O5 (Ru-Ta2O5). The TEM reveals that Pt nanoparticles with an average diameter of ca. 4.0 ± 0.5 nm were uniformly distributed on the Ru-Ta2O5. The further electrochemical characterizations including cyclic voltammograms (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) methods show that Pt/Ru-Ta2O5 catalysts have larger electrochemical surface area, better electrocatalytic activity, and higher stability toward the methanol oxidation reaction compared to the pure Ta2O5 supported Pt catalysts. The excellent electrocatalytic performance is mainly contributed to the improvement of Ru for the dispersion of Pt nanoparticles, the increased conductivity of Ta2O5, as well as the promotion of oxidation reactivity by Ru. This work demonstrated that Ru-Ta2O5 is a promising anode catalyst support for direct methanol fuel cells.

Free-standing flexible supercapacitive electrodes have practical application for wearable energy storage devices. In this paper, graphene paper (GP), a flexible electrode substrate, was prepared by one-step reduction of graphene oxide (GO) using HI solution. GP can be used independently as a flexible electrode with specific capacitance of 227 F/g. In order to make up for the shortage of GP specific capacitance storage, polyaniline (PANI) with high specific capacitance and good electrical conductivity was selected to composite with GP by electrochemical polymerization approach. This method to fabricate electrode material by direct electrochemical polymerization avoids the use of conductive binder and organic solvent. Owing to the specific capacitance contribution of PANI and GP, the PANI/GP composites exhibit higher specific capacitance when the polymerization time is 30 s and the polymerization voltage is 0.8 V. At 1 A/g current density, the specific capacitance of composite is up to 759 F/g, which is 3.34 times of neat GP.

Composite supercapacitive materials can combine two different kinds of electrode materials with different energy storage mechanisms, as well as present enhanced supercapacitive performance. In this paper, a reduced graphene oxide aerogel (GA) was prepared with an adjustable pore structure and used as a matrix for loading of secondary active material (MnO2) through an electrochemical deposition method. The influences of the deposition time and deposition voltage on the electrochemical behaviors and specific capacitances of MnO2/GA composites were studied. The unique three-dimensional porous structure of GA can act as a good matrix for MnO2. The results show that when the deposition time is 30 s and deposition voltage is 1.0 V, the MnO2/GA composite has the highest specific capacitance of 664 F/g at a current density of 1 A/g. Compared with neat GA, the specific capacitance of the MnO2/GA composite is enhanced by 190%, which can be assigned to the co-contribution of two kinds of active materials, a facile ion diffusion path through the porous structure, and good electron conductivity of the GA.

A Poly (3, 4-dioxyethylthiophene)–Carbon Nanotubes (PEDOT–CNT) composite electrochromic material, connected by interfacial covalent bonds, was successfully synthesized by electrochemical copolymerization of 3, 4-dioxyethylthiophene with thiophene-2-methylamine functionalized CNT. The molecular and aggregate structures of PEDOT–CNT were investigated by Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy. The electrochemical behavior and electrochromic properties of PEDOT–CNT were measured by CV (cyclic voltammetry), UV–Vis (ultraviolet visible spectroscopy) and EIS (electrochemical impedance spectroscopy). The test results show that the electrochromic performance of PEDOT–CNT is better than that of neat PEDOT. As the percentage of carbon nanotubes increases, the contrast and response speed of the composites increase accordingly. The PEDOT film has a contrast under square-wave potential of 0.54, a coloring time of 6.42 s, and a fading time of 2.54 s. Compared with PEDOT, the contrasts of PEDOT–CNT-3%, PEDOT–CNT-5% and PEDOT–CNT-7% are increased by 31%, 33%, and 89%, respectively. The response speeds of PEDOT–CNT-5% increase to coloring time of 3.51 s and fading time of 1.37 s.

A facile hydrothermal strategy is adopted to synthesize the composite of NiCo-layered double hydroxide(NiCo-LDH) with biomass carbon as substrate for supercapacitor electrodes. The prepared NiCo@BC was characterized by means of X-ray diffraction(XRD), scanning electronic microscopy(SEM), Fourier transform infrared spectroscopy(FTIR) and Raman spectroscopy, and electrochemical tests. The SEM images demonstrated that numerous NiCo-LDH nanosheets directly grew on the surface of biomass carbon uniformly. Electrochemical tests indicated that the NiCo@BC electrode exhibited good capacitive behavior with a specific capacitance of 606.4 F/g at the current density of 0.5 A/g. In addition, the composite electrode showed excellent cyclic stability of 87.1% even after 1000 cycles. These results manifest that NiCo@BC nanocomposite is a promising candidate for the electrode material for future supercapacitor practical applications.

In this paper, we prove an efficient and facile synthesis method for preparing PtRu nanoparticles (NPs)/graphene nanosheets (GNS) catalysts for methanol electrooxidation. Our approach employed carboxylated-graphene nanosheets (C-GNS) as the support which prepared by the Friedel-Crafts reaction between succinic anhydride and GNS. The reaction conditions are mild without cumbersome pretreatment of GNS. The morphology and component of PtRu NPs/C-GNS catalysts were characterized by transmission electron microscopy (TEM) and inductively coupled plasma-atom emission spectroscopy (ICP-AES), respectively. The TEM observation reveals that PtRu NPs with an average diameter of ca. 4.0 ± 0.5 nm uniformly distributed on the edges and wrinkles of C-GNS. The further electrochemical characterizations including cyclic voltammograms (CV) and chronoamperometry (CA) methods show that PtRu NPs/C-GNS catalysts have significantly higher electrocatalytic activity and stability toward methanol electrooxidation compared to the PtRu catalysts supported on the unmodified GNS. This provides an easy approach to synthesize GNS-based electrode materials for high-performance energy conversion devices in the future.

As electrode materials, metal-organic frameworks always have low electrical conductivity and poor structural stability, which limits its applications in electrochemical fields. Here, Ni-BPDC/GO composites are synthesized using graphene oxide (GO) as a substrate and 4,4′-biphenyldicarboxylic acid (BPDC) as an organic ligand via a hydrothermal approach. The growth mechanism of the Ni-BPDC and Ni-BPDC/GO composites is proposed. In the composites, highly dispersed Ni-BPDC macro-nanostrips are supported on the GO surface in parallel. The presence of GO does not affect the growth and crystalline structure of Ni-BPDC. Compared with the Ni-BPDC, Ni-BPDC/GO composites exhibit higher specific capacitance, rate capability, and operating current density through lowering intrinsic resistance, charge-transfer resistance, and ion diffusion impedance. Moreover, the assembled Ni-BPDC/GO-3//reduced graphene oxide (rGO) asymmetric supercapacitor has large specific capacitance, good cycling stability, and high energy density (16.5 W h/kg at 250 W/kg). Hence, Ni-BPDC/GO composites are a potential electrode material for supercapacitors.

Polyaniline nanotubes (PANI-T) and graphene oxide (GO) have been compounded by a postcomposition method with the assistance of electrostatic adsorption. Using this so-called postcomposition method, both the electric double-layer capacitance of the GO and the pseudocapacitance of the conducting polymer can be utilized. PANI-T prepared by a rapid mixing method was positively charged by pretreatment with (3-aminopropyl)triethoxysilane (APTES). PANI/GO composites were obtained by mixing the positively charged PANI-T and negatively charge GO with the assistance of electrostatic attraction. Charge–discharge measurements in 1 mol L−1 H2SO4 aqueous electrolyte revealed that the specific capacitance of PANI-T/GO-10% could reach 1220 F g−1 at a current density of 0.5 A g−1, being much higher than the value of 648 F g−1 for PANI-T. After 500 cycles of charge–discharge testing, the composite retained 97% of its capacitance. These enhanced supercapacitive properties can be attributed to the two types of energy storage mechanism and the electrostatic interaction between GO and PANI-T. Preparation of such PANI-T/GO composite electrode materials by electrostatic adsorption thus provides an efficient approach for improvement of the supercapacitive properties of conducting polymers or metal oxides.

Multiferroic YFeO3 nanofibers were prepared by electrospinning. The as-prepared nanofibers were characterized by XRD, TG-DTA, SEM and Raman spectrum. The magnetic property and photocatalytic activi...

In this paper, water-dispersible and covalently bonded polyaniline-carbon nanostructures, including polyaniline-reduced graphene oxide (PANI-rGO), polyaniline-single-walled carbon nanotubes (PANI-SWCNTs), and polyaniline-reduced graphene oxide/single-walled carbon nanotube (PANI-rGO/SWCNTs) nanocomposites, were synthesized by grafting PANI onto p-phenylenediamine (PPD)-functionalized graphene oxide (GO) or single-walled carbon nanotubes (SWCNTs) using polystyrene sulfonate (PSS) as a macromolecular dopant agent. The structures and morphologies of the PANI, PANI-rGO, PANI-SWCNTs, and PANI-rGO/SWCNTs nanocomposites were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The cyclic voltammetry and UV–vis spectra were performed on an electrochemical workstation and a UV–vis spectrometer, respectively. The results show that the electrochromic and electrochemical properties of nanocomposites can benefit from the high conductivity of SWCNTs and the abundant active sites of rGO. When SWCNTs and rGO work together, their respective shortcomings are overcome, allowing the nanocomposite to exhibit the best electrochemical and electrochromic properties. The optical contrast increased from 0.38 for PANI to 0.52 for PANI-rGO/SWCNTs. The coloring and bleaching times decreased from 2.59 s and 2.39 s, respectively, for PANI to 1.33 and 0.78 s, respectively, for PANI-rGO/SWCNTs. The charge transfer resistance (Rct) decreased from 135 Ω for PANI to 30 Ω for PANI-rGO/SWCNTs. The synergistic effect of PANI, rGO, and SWCNTs can significantly improve the electrochromic ability of PANI. Electrochromic properties of covalently bonded polyaniline-reduced graphene oxide/single walled carbon nanotubes nanocomposites. A high performance electrochromic material was prepared using polyaniline (PANI) and two different dimensional carbon nanostructures, single-walled carbon nanotubes (SWCNTs) and reduced graphene oxide (rGO) as the components. The covalent bond was introduced to interface between PANI and two carbon nanostructures to form a three-dimensional conductive network. Owing to the high electron conduction through directly connected covalent bond and loose molecular chain aggregation brought by two various dimensional carbon nanostructure, PANI-rGO/SWCNTs nanocomposites exhibit superior electrochemical and electrochromic properties (high optical contrast and short switching time) compared with PANI.

Polyaniline is one of the most common electrode materials for supercapacitors. The morphology of polyaniline directly affects the properties of polyaniline. In this paper, a new method for preparing hollow polyaniline nanospheres is described. Polyaniline-S with solid and hollow structures are successfully synthesized by the hydrothermal method, through varying the amounts of the catalyst and oxidant. The prepared hollow nanospheres have uniform particle size, a smooth surface, and uniform wall thickness. The hollow structure provides rapid permeability to the material, facilitating the transfer and transport of charges and ions in the electrolyte, and it can also act as an ion storage tank to increase the accumulation of ions inside. The specific capacitance of polyaniline-S is high at 235 F g-1 at 0.5 A g-1. To reduce the aggregation of polyaniline-S and improve the electrochemical activity, polyaniline-S, and graphene oxide are composited using the interfacial electrostatic interaction. The content of graphene oxide has a significant influence on the electrochemical performance of the composites. The specific capacitance of the polyaniline-S/ graphene oxide composite with a 10% loading amount of graphene oxide reaches 535 F g-1 at 0.5 A g-1, increase of nearly 128% compared to representing a significant polyaniline-S. The specific capacitance retention rate is 93.6% after 10,000 cycles.

In this study, polyaniline (PANI) nanostructures with different morphologies (nanofibers, nanotubes, and nanospheres) were obtained via interfacial polymerization, rapid mixing reaction, and hydrothermal method. The influences of the synthesis methods on the morphologies and supercapacitive properties of PANI nanostructures were investigated. The chemical structures of materials were characterized by Fourier-transform infrared and Raman spectroscopies. Scanning electron microscopy and transmission electron microscopy images were used to explore the morphologies of PANI nanostructures. N2 adsorption–desorption isotherm, cyclic voltammetry, charge–discharge test, and electrochemical impedance spectroscopy were used to characterize the pore distribution, electrochemical, and supercapacitive properties of PANI nanostructures. The results show that PANI nanotubes (PANI-T) exhibit the best electrochemical performances among three kinds of PANI nanostructures. The PANI-T exhibits high specific capacitances of 648 and 290 F g−1 at current densities of 0.5 and 10 A g−1, respectively, indicating its good supercapacitive property and rate capability. The enhanced electrochemical and supercapacitive performances can be attributed to its hollow nanotube structure.

In this article, a high specific capacitance biomass carbon/MnO2 nanocomposites electrode materials were prepared by hydrothermal method. The porous sugarcane bagasse based biomass carbon was used as the host to load MnO2 nanospheres. The final obtained nanocomposites exhibit high specific capacitance. Besides, the effects of different electrolytes on the electrochemical properties of sugarcane bagasse carbon (SBC)/MnO2 nanosphere composites (SBC/MnO2) were also investigated. In comparison with MnO2 nanospheres, the specific capacitances of the SBC/MnO2 composite materials are improved whether in alkaline electrolyte or neutral electrolyte. Especially, in 1 M Na2SO4 electrolyte, the specific capacitance of SBC/MnO2 composite is up to 747 F·g−1 at a current density of 1 A·g−1, which is much higher than the MnO2 nanospheres at the same current density. At the same time, after 1000 cycles of charge–discharge process in a neutral electrolyte, the specific capacitance retention of SBC/MnO2 composite reaches 77%.

In view of the poor electronic conductivity and inferior structural stability, the direct application of Metal-Organic Frameworks (MOFs) as an electrode material is limited. Herein, the carboxylated multi-wall carbon nanotubes (MWCNT) are utilized as a substrate for the in-situ growth of bimetallic NiCo-based MOFs (NiCo-MOF). The flower-string-like NiCo-MOF/MWCNT composites are successfully synthesized using 4, 4′-biphenyldicarboxylic acid (BPDC) as a ligand via a simple solvothermal approach. In the composites, MWCNT is wrapped with 2D NiCo-MOF nanosheets through some bonds or affinity between MWCNT and NiCo-MOF. Meanwhile, the MWCNT presence does not affect the formation of the NiCo-MOF crystals. Compared with the hydrangea-like NiCo-MOF microspheres, the flower-string-like composite structures are more loosely assembled by NiCo-MOF nanosheets. Owing to the guiding effect of MWCNT on the NiCo-MOF growth, many well-dispersed flower-string-like structures can be achieved by adjusting MWCNT dosages. Due to the unique hierarchical structure and good synergistic effect, the NiCo-MOF/MWCNT composites exhibit excellent capacitance performances. The optimal composites demonstrate a large specific capacitance of 1010 F g−1 at 0.5 A g−1, a good rate capability (760 F g−1 even at 10 A g−1), a good cycling stability and reversibility with the capacitance retention of 828 F g−1 (100% of the initial capacitance) and coulombic efficiency of approximate 98% at 5 A g−1 after 3000 cycles, a low internal resistance and charge transfer resistance. The asymmetric supercapacitor assembled by NiCo-MOF/MWCNT composites as electrode materials has high energy density even at high power density, good rate capability, excellent cycling stability and reversibility. Hence, the as-synthesized NiCo-MOF/MWCNT composites are a promising high-performance electrode material for supercapacitors.

In this article, polyaniline nanofibers (PANI-NF)/manganese dioxide composites (PANI/MnO2) were synthesized through an interfacial polymerization approach. The PANI-NF and MnO2 were obtained by in situ oxidation of aniline by potassium permanganate and in situ reduction of potassium permanganate by aniline, respectively. During the interfacial polymerization, the monomer aniline can only be oxidized to PANI after it diffuses into the water phase. This diffusion-control feeding process of the monomer results in nanofiber structure. The morphologies and crystal structures of the prepared PANI/MnO2 composites were measured by scanning electron microscopy and x-ray diffraction. The supercapacitive behaviours of these composites were analysed by cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) tests. The CV and GCD tests indicate that the PANI/MnO2 composites possess better electrochemical activity and higher capacitive properties compared to neat PANI nanofibers. The specific capacitance of PANI/MnO2 composites and PANI-NF are 751 F g−1 and 180 F g−1 at 0.2 A g−1 in Na2SO4 solution, respectively. We believe that the enhanced capacitive properties are related to the special nanostructure and strong interaction between PANI and MnO2 that resulted from the interfacial synthesis method.

Polyaniline nanowires (PANI NWs) were synthesized under different temperatures through a facile hydrothermal method and used as electrodes for high-performance pseudocapacitor. The resulting samples were analyzed by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron micrographs, thermogravimetric analysis, and X-ray photoelectron spectroscopy. Electrochemical properties of these PANI electrodes are studied by cyclic voltammetry, galvanostatic charge–discharge test, and electrochemical impedance spectroscopy in 0.5M H2SO4 aqueous solution. The highest specific capacitance is obtained on the PANI NWs synthesized under 80°C (PANI-80) with 540.0 F g−1 at current density of 0.5 A g−1 accompanied with 82% specific capacitance retention after 1000 charge discharge cycles at 5 A g−1 current density.

In this article, polyaniline nanofibers/reduced graphene oxide (PANI-NFs/rGO) nanocomposites were prepared by a one-pot hydrothermal method. Under the condition of high temperature and high pressure, graphene oxide (GO) was reduced to rGO and aniline was in-situ polymerized to form PANI-NFs using ammonium persulfate as oxidant. The morphologies and structures of PANI-NFs/rGO nanocomposites were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), and Raman analysis. The results show that PANI-NFs uniformly grow on the surfaces of rGO sheets, which can act as spacers to prevent the aggregation of rGO. Combining with FTIR and Raman analysis, it can be concluded that PANI-NFs/rGO nanocomposites are successfully prepared. The electrochemical performances of PANI-NFs/rGO nanocomposites were tested by cyclic voltammetry and galvanostatic charge–discharge. The PANI-NFs/rGO nanocomposites exhibit superior electrochemical performances compared to the PANI-NFs. With 10 wt% of GO loaded, the PANI-NFs/rGO nanocomposite exhibits highest specific capacitance of 942 F g−1 at a current density of 1 A g−1. The PANI-NFs/rGO nanocomposites also demonstrate good rate capacity and high cycling stability under the high discharging current density (10 A g−1), the specific capacitance can still reach to 680 F g−1. After 1000 charge–discharge cycling at a current density of 5 A g−1, 78% of specific capacitance can be retained. The enhanced capacitive performances can be attributed to the facile electron conduction pathway brought by the even distribution of highly conductive rGO nanosheets.

With the increasing demands for the high efficiency of pulp-mixing, which is adapted to the fine particles entering into flotation section, an intensification pulp-mixing device with novel design has been developed. On the basis of numerical simulation, which indicated efficient circulation and shear effect of the “maleic-cutting” configuration equipped with static-guide-blade, the power dissipation amount PV, mixing time θm, power number NP, mixing time number Nθ, CS which reflects shear property, suspension percentage φ/Φ(%), and concentration variance σ2 were measured, analyzed and compared with the ordinary agitated tank. Combining with actual mineral separation tests, performance of the efficient pulp-mixing device characterized by “multi-stage and compulsory” has been validated: the “multi-stage and compulsory” mixing device corresponds to a different circulation/shear energy; under the same operating conditions, the absolute advantages in the aspect of mixing time are the root cause for the increase of mixing efficiency; the “maleic-cutting” configuration is less influenced by pulp-mixing time and has the characteristics of achieving fast mixing; the strong shear effect mechanism is the root cause for the realization of pulp-mixing intensification on fine-particle and microfine-particle materials. Therefore, the “multi-stage and compulsory” mixing device designed by this research successfully accomplished intensification of pulp-mixing effect.

NiCo-based bimetal-organic frameworks (NiCo-MOF) are synthesized via a hydrothermal approach, using 4,4′-biphenyldicarboxylic acid (BPDC) as a ligand. Structural characterizations find that NiCo-MOF is composed of one-dimensional micro-nanorods and regular three-dimensional cuboids assembled by one-dimensional micro-nanorods，possessing a good crystalline structure, in which nickel and cobalt ions have been coordinated to the BPDC ligands. Moreover, NiCo-MOF can be stable below 300 °C in air. The electrochemical measurements show that GCD activation at a high current density can significantly increase the capacity of NiCo-MOF due to decreasing the charge-transfer resistance and ion diffusion impendence. The specific capacitance of NiCo-MOF reaches 990.7 F/g from 156.5 F/g at 1 A/g, and the coulombic efficiency increases to 98.0% from 77.6% after the CV-GCD activation. Activated NiCo-MOF exhibits prominent pseudocapacitive behaviors, high specific capacitances at different current densities and a good cycling stability after 1000 cycles. The capacity of NiCo-MOF is up to 405.0 F/g when the current density increases to 20 A/g, and remains 553.2 F/g at 1 A/g after 3000 cycles. Compared with monometallic Ni-MOF and Co-MOF, bimetallic NiCo-MOF possesses a much higher capacity at different current densities due to the lower intrinsic resistance, charge-transfer resistance and ion diffusion impendence.

In this study, Prussian blue@Carbon-dot (PB@C-dot) hybrids have been developed by one-step hydrothermal method. The incorporation of C-dots into Prussian blue thin film as a way of improving its electrochromic performance was investigated. The structure of the PB@C-dot hybrid was characterized through X-ray diffraction, Raman spectroscopy and scanning electron microscopy. The electrochromic properties showed that incorporation of 10 mL C-dots into the film showed higher optical contrast of 1.6 and superior coloration/bleaching response of 10 and 3 s. It is proposed that the C-dots component used in the construction of the PB@C-dot hybrid plays a key role to achieve superior electrochromic performance.

Two-dimension covalent organic frameworks (2D COFs) are porous materials with the interlayer π-π interaction and excellent optoelectronic properties. Their adjustable porous structure and designable molecular structure endow them unlimited possibilities in the field of optoelectronic materials and other functional materials. In this paper, 2D COF electrochromic films were prepared by solvothermal synthesis method with different amounts of functionalized carbon nanotubes (FCNT) loading to improve their conductivity. The morphology characterization of COFDAAQ-TFP reveals its intertwined nanofiber structure. The electrochromic performance of COFDAAQ-TFP film shows that the color of COFDAAQ-TFP and FCNT-COFDAAQ-TFP have a reversible transformation from orange to dark brown during the redox process. When the loading amount of FCNT is 1%, FCNT-COFDAAQ-TFP exhibits best electrochromic properties, which has a contrast of 0.358 and coloring time of 5.7 s. Relative to COFs, FCNT-COF has enhanced contrast and stability, which is a potential electrochromic material in many fields such as smart window and smartphone back case.

Using coal-based polyaniline as a carbon and nitrogen source, N-doped porous carbon (NPC)/nickel cobalt oxides (NixCoyOz)/carbon micro–nanotubes (CMNT) composites possessing rich nanoscale meso–macropores, spinel NiCo2O4 sheets and multi-walled CMNT are successfully synthesized by the first pyrolysis and the second wet oxidation process. Therein, CMNT owning a diameter of 10–200 nm and a length of several micrometers is grown by a two-stage furnace process in a hydrogen-free atmosphere, using nickel acetate as a growth catalyst precursor. CMNT exhibits polymorphic features, including most curved tubes, a few vertical tubes, some bamboo-like tubes and some Chinese-sugar-gourd-skewer-like tubes, resulting from the diversity and low hydrogen content of gaseous cracking products from coal-based polyaniline. Carbon in CMNT mainly exists in the graphitic state while carbon in NPC mainly presents in the amorphous state. Nitrogen in CMNT mainly exists in the form of graphitic N while nitrogen in NPC (0.89 wt% in composites) mainly presents in the form of pyrrolic N (74.4 at.%) and oxidized N (25.6 at.%). The intercalated Ni and Co impurity in NPC and CMNT are transformed to most NiCo2O4 and a few NiO. The BET specific surface area and average pore width of composites are 169.3 m2/g and 8.4 nm. CMNT incorporation obviously improves capacitance properties of NPC/NixCoyOz/CMNT composites. The composites demonstrate a higher specific capacitance of 598.4 F/g at 1 A/g, and a good cycling stability retaining a high capacity of 190.1 F/g (81.1% retention) at 5 A/g after 5000 charge–discharge cycles. It is attributed to the nitrogen incorporation of porous carbon, high conductivity and large specific surface area of CMNT, and high electrochemical activity of NixCoyOz, especially, the synergistic effects of NPC, CMNT and NixCoyOz. This study has developed a polygeneration process for coal pyrolysis, which also enables the combined utilization of coal pyrolysis products.

In this article, we reported a biomass carbon/MnO2 nanocomposite electrode material prepared by a hydrothermal method. Sugarcane bagasse and KOH were the carbon source and activation agent, respectively. The obtained sugarcane bagasse carbon is rich in pore structure, so it can act as the host for MnO2. The biomass carbon/MnO2 nanocomposite electrode was prepared by a hydrothermal method. The morphologies of materials were observed by scanning electron microscopy. Raman spectra and x-ray diffraction were utilized to characterize the molecular and crystal structures of samples, respectively. The electrochemical and capacitive performances of materials were tested by electrochemical workstation. By calculation, the specific capacitance of sugarcane bagasse carbon, MnO2 and composite electrode are 280 F g−1, 163 F g−1 and 359 F g−1, respectively. Compared with pure sugarcane bagasse carbon and MnO2, the specific capacitance of the composite increases by 28% and 120%, respectively. After 2000 cycles of charge and discharge, the capacitance retention of the composite is 94%, which is higher than 91% of sugarcane bagasse carbon and 45% of MnO2.

A novel synthesis approach of N-doped porous carbon (NPC)/NiO composites possessing some honeycomb-shaped nanoporous carbon and plentiful NiO nanosheets is exploited. First NPC/Ni composites are achieved with NPC yield of 52.9% through a catalytic pyrolysis method, using coal-based polyaniline particles prepared by an in-situ polymerization method as a carbon and nitrogen source, and nickel particles as a catalyst, respectively. Next NPC/NiO composites are achieved unexpectedly with plentiful NiO nanosheets and N content of 1.00 wt% after a liquid oxidation process. In NPC/NiO composites, porous carbon mainly presents in the amorphous state, while the incorporated nitrogen mainly presents in the form of pyrrolic N (92.9 at.%) and oxidized N (7.1 at.%). Plentiful NiO nanosheets are embedded in the pores or on the NPC surface. 33.3 at.% Ni2O3 components exist in the surface of NiO nanosheets. NPC/NiO composites possess not only rich micropores, but also significant mesopores and nanoscale macropores. The BET specific surface area, BET average pore width and BJH adsorption average pore diameter are 627.5 m2/g, 2.0 nm and 5.1 nm, respectively. NPC/NiO composites demonstrate a high specific capacitance of 404.1 F/g at 1 A/g, and a good cycling stability maintaining high specific capacitance of 212.4 F/g (84.3% of the initial capacitance) at 5 A/g after 5000 cycles of charge and discharge, attributed to some honeycomb-shaped nanopores of carbon and large specific surface area of NiO nanosheets, and the synergistic effects between electric double-layer capacitance of NPC and pseudocapacitance of NiO. This study may provide a novel approach for the value-added applications of low-rank coal.