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Herein, Ni-doped Mn2O3 microspheres are successfully synthesized via the facile coprecipitation of metal ions and ammonium bicarbonates, followed by a heat treatment process. Ni-doped Mn2O3 exhibits outstanding catalytic performance toward the oxygen reduction reaction (ORR) in alkaline media with a half-wave potential of 0.801 V, limiting current density of 6.02 mA cm−2 at 0.6 V vs. RHE, outstanding long-term durability, and strong tolerance to methanol. Furthermore, a Zn–air primary battery using Ni-doped Mn2O3 as an air cathode shows high open-circuit voltage of 1.52 V and high power density of 88.2 mW cm−2, outperforming the commercial Pt/C cathode. The exceptional performance of the Ni-doped Mn2O3 microspheres is ascribed to the hierarchical structure, optimized particle size, and Ni incorporation into Mn2O3. The proposed synthesis strategy provides a new methodology for the design and fabrication of electrochemically active transition metal-doped materials as efficient electrocatalysts for a variety of energy storage and conversion reactions.

Herein, a strongly coupled Cu3P/FeP heterostructure with P-doped carbon derived from MIL-101 was synthesized via a three-step method involving solvothermal, carbonization, and phosphidation processes. The Cu3P/FeP heterostructure serves as a good catalyst because it possesses abundant interfaces between Cu3P and FeP, which enables the exposure of electrocatalytically active sites and tuning of surface electronic configurations. Additionally, the presence of strong heterointerfaces between Cu3P and FeP, and the integration of the P-doped carbon guarantee the high electrical conductivity of the catalyst. Benefiting from these advantages, the Cu3P/FeP electrode exhibited outstanding electrocatalytic activity toward the oxygen evolution reaction (OER), which presents a low overpotential of 315 mV to drive a current density of 10 mA cm−2 in 1.0 M KOH, thus outperforming that of the state-of-the-art RuO2. In addition, the Cu3P/FeP hybrid composite exhibited long-term stability for 50 h. This work provides a new strategy for the design and preparation of transition-metal-based heterostructures and facilitates the development of high-performance energy-related materials.

Transition metal-based heterostructure materials are considered as promising alternatives to state-of-the-art noble metal-based catalysts toward the oxygen evolution reaction (OER). Herein, for the first time, a simple interface engineering strategy is presented to synthesize efficient electrocatalysts based on a novel CoFe2O4/β-Ni(OH)2 heterogeneous structure for the electrochemical OER. Remarkably, the optimized CoFe2O4/β-Ni(OH)2 electrocatalyst, benefiting from its hierarchical hexagonal heterostructure with strong electronic interaction, enhanced intrinsic activity, and electrochemically active sites, exhibits outstanding OER electrocatalytic performance with a low overpotential of 278 mV to reach a current density of 10 mA cm−2, a small Tafel slope of 67 mV dec−1, and long-standing durability for 30 h. Its exceptional OER performance makes the CoFe2O4/β-Ni(OH)2 heterostructure a prospective candidate for water oxidation in alkaline solution. The proposed interface engineering provides new insights into the fabrication of high-performance electrocatalysts for energy-related applications.

Dielectric elastomer actuators (DEAs), a type of electroactive polymers (EAPs), are smart materials that are used in various fields such as artificial muscles and biomimetic robots. In this study, graphene nanoplatelets (GNPs), which are conductive carbon fillers, were added to a widely used DEA, namely, polydimethylsiloxane (PDMS), to improve its low actuated strain. Four grades of GNPs were used: H5, H25, M5, and M25 (here, the number following the letter indicates the average particle size of the GNPs in μm). The average layer thickness of the H grade is 13–14 nm and that of the M grade is 5–7 nm. PDMS composites were prepared by adding 0.5, 1, 2, and 3 wt% of each GNP, following which the mechanical properties, dielectric properties, and actuated strain of the composites were measured. The mechanical properties were found to increase as the particle size increased. Regarding the dielectric characteristics, it was found that the higher the aspect ratio of the filler, the easier the formation of a micro-capacitor network in the composite—this led to an increase in the dielectric constant. In addition, the higher amounts of GNPs in the composites also led to an increase in the dielectric constant. For the actuated strain analysis, the electromechanical sensitivity was calculated using the ratio of the dielectric constant to the Young’s modulus, which is proportional to the strain. However, it was found that when the loss tangent was high, the performance of the actuated strain decreased owing to the conversion of electric energy into thermal energy and leakage current loss. As a result, the highest actuated strain was exhibited by the M25 composite, with an actuated strain value of 3.01% measured at a low electric field (

With the aim to develop electrically conductive adhesives (ECAs) as alternatives for traditional lead-based or lead-free solders in electronic packaging, we report an outstanding enhancement of electrical conductivity of epoxy ECAs filled with silver nanoparticles (AgNP)-decorated graphene nanoplatelets (AgNP@GNP). In order to avoid the deterioration of the superior properties of GNP, the GNP is directly sensitized by Sn precursor without conventional harsh-conditioned graphene oxide (GO) preparation, followed by the decoration of AgNP on sensitized GNP. The structural and morphological properties of AgNP@GNP were characterized using XRD, TEM, Raman, and TGA. The excellent distribution of SnO2 and AgNP on GNP could be explained by the attractive force between protonated GNP (pH +20 mV) and lone-paired stannous ions. The electrical conductivity of as-prepared AgNP@GNP (1.3 × 105 S/cm) was nearly 6500 times than that of pristine GNP. Moreover, the electrical conductivity of the 20 vol% AgNP@GNP/epoxy ECAs was almost 500 times higher than that of pristine GNP/epoxy and 27-fold higher than that of conventional AgNP@GO/epoxy ECA.

This paper reports the synthesis of various molar concentrations of manganese (Mn)-doped Ultra-High Surface area Activated Carbon (USAC) additives and their efficient use as cathode materials for supercapacitors. We synthesized the nanoparticles via a novel and facile dip-coating process and characterized them in detail by various analytical techniques. The SEM, EDAX, and XPS results showed that the Mn ions were successfully substituted on the USAC additives’ layered structure without any structural changes. The long cyclic stability of the as-prepared Mn-doped USAC additives was tested as a cathode material for supercapacitors at different current densities. The detailed experimental results showed that the Mn dopant content crucially determines the electrochemical performances of the USAC additives. Electrochemical measurements showed that the MnCEP-S600HTT with 0.10 mol% molar concentration of Mn dopant gives the best cycling performances. It delivers a discharge capacity of 262.9 mAh g−1 after 100 cycles. Further increasing the current density to 1000 mA g−1 allowed it to still maintain 253.6 mAh g−1 after 200 cycles. We confirmed that the structure of Mn-doped USAC additives is an important pole to improve the structural stability and electrochemical properties.

Herein, we report the synthesis of a strongly coupled Co3O4/CoS microbox heterostructure, prepared through an annealing treatment with the subsequent hydrothermal sulfidation of a Co–Co Prussian blue analog (PBA) precursor. The unique 3D hierarchical architecture and potential synergies of Co3O4 and CoS provide benefits to the Co3O4/CoS heterostructure for both oxygen reduction and evolution reactions (ORR and OER). It displays comparable ORR catalytic activity (half-wave potential of 0.820 V) to state-of-the-art Pt/C but better durability and methanol tolerance. The Co3O4/CoS electrocatalyst also shows high OER activity with a relatively low overpotential (349 mV at 10 mA cm−2) and small Tafel slope (66.6 mV dec−1), compared to those of commercial RuO2 (366 mV at 10 mA cm−2 and 86.3 mV dec−1, respectively), making it a potential bifunctional electrocatalyst for both the ORR and the OER. Moreover, a rechargeable Zn–air battery with a Co3O4/CoS cathode shows a higher cell voltage (1.51 V), higher power density (168 mW cm−2 at 269 mA cm−2), and better cycling stability (up to 150 cycles) than the same battery with the state-of-the-art Pt/C + RuO2 catalyst. This PBA-based material with a strongly coupled interface between Co3O4 and CoS offers insights into the development of low-cost and highly efficient electrocatalysts for diverse energy-related applications.

In this study, binary NiFe alloy nanoparticles are successfully prepared using a simple hydrothermal method followed by H2 reduction. The nanoparticles are then applied as electrocatalysts for oxygen evolution reaction (OER). Compared to unary Ni or Fe, the binary NiFe alloy electrocatalyst exhibits a much lower overpotential of 298 mV at a current density of 10 mA cm−2, and it exhibits electrocatalytic activity for OER superior to that of state-of-the-art RuO2 and IrO2 noble metal oxide catalysts. Moreover, the alloy catalyst exhibits substantial long-term durability after 1000 cyclic voltammetry tests. This remarkable electrochemical performance mainly originates from the synergistic effects of Fe incorporation into Ni species, leading to the improved charge transfer kinetics and intrinsic activity of the catalyst. These results provide a promising avenue for developing cost-effective and high-performance electrocatalysts as advanced electrodes for energy storage and conversion systems.

Graphite exhibits electromagnetic wave attenuation and high electrical conductivity. In this study, we analyzed the electromagnetic interference shielding effectiveness (EMI SE) performance and electric conductivity of composites fabricated by varying the size (mean size: 6–100 µm) of graphite fillers and explained resulting attributes through the relative permittivity and geometrical characteristics of the filler. When the graphite/paraffine wax composite was fabricated using large-sized graphite (KS150), the spacing between the graphite fillers became widened, enabling electromagnetic waves to leak through the gap. The analysis results indicated that KS150 graphite exhibited an EMI SE performance of under 10 dB when the filler content was 30 wt%. However, when the content was increased to 50 wt%, the EMI SE performance improved sharply to 40 dB. In contrast, when the composite was filled with small-sized graphite (KS6), having a high ratio of surface to volume, the EMI SE performance was greater than that with the largesized graphite at low loading. The results related to the EMI shielding performance of graphite-filled composites revealed that the size of the filler greatly affects the EMI SE. The composite using KS75 showed an EMI SE performance of 53.0 dB and electrical conductivity of 2,000 S/m.

As environmental issues continuously increase, the development of effective and eco-friendly catalytic systems in organic chemistry is of great importance. To achieve this goal, two representative ...

Herein, interfacially coupled Ni/Ni(OH)2 nanocomposites are successfully prepared using a facile one-step hydrothermal route with addition of various amounts of hydrazine and then applied as bifunc...

Spinel-type nickel cobaltite with numerous oxygen vacancies is successfully synthesized by hydrothermal and thermal reduction using hydrogen. The effects of oxygen vacancies on the electrochemical activity and stability for the oxygen reduction reaction are investigated. The prepared catalyst displays significantly enhanced oxygen reduction reaction (ORR) catalytic performance under alkaline conditions, which is comparable to that of commercial Pt/C. The oxygen-deficient NiCo2O4 exhibits a very high limiting current density of −5.44 mA cm−2 with onset and half-wave potentials of 0.93 and 0.78 V versus the reversible hydrogen electrode (RHE), respectively. Additionally, it shows excellent durability and resistance to methanol. The enhanced ORR activity and stability of the catalyst can be ascribed to the synergistic effects of the relatively large electrochemical surface area, more exposed active sites, and good electrical conductivity derived from abundant oxygen vacancies.

Novel palladium complexes composed of palladium and a conjugated ligand (imine–aldehyde) were immobilized on graphene oxide. The developed catalyst was characterized by XPS, and TEM. The novel catalyst was proven to be highly efficient for the Suzuki-Miyaura coupling reaction of aryl halides (Br, Cl) with arylboronic acids under mild conditions with a low amount of catalyst (0.1 mol%). In particular, excellent yields could be also obtained at room temperature within 1 h for monosubstituted aryl bromide coupling. Furthermore, the novel catalyst could be reused at least ten times without significant loss of its catalytic activities.

Water pollution due to heavy metal ions from factories causes serious threats as the heavy metal ions are inclined to accumulate in living systems threat ening their health. Adsorption is considered one of the most promising wastewater purification techniques for its simple operation and high effectiveness compared with other techniques. Accordingly, a novel cost-effective and environmentally benign porous melamine-vanillin polymer (MVP) was synthesized via Schiff-base formation reaction, which was utilized for the removal of Pb(II) ions. The MVP achieved a high surface area of 745 m2 g-1 with a hierarchically porous structure consisting of 1 nm and 3–50 nm pores. Effects of the contact time and the initial heavy metal concentration on the adsorption of Pb(II) were studied. Due to the copious functional groups and the hierarchical pore size distribution, MVP was found to exhibit a good adsorption performance toward Pb(II) ions. The adsorption process was well-fitted to the Langmuir adsorption isotherm and the pseudo-1st-order kinetic model.

Nitrogen and sulfur co-doped porous carbon (NSDPC) is successfully prepared by impregnation and carbonization using a zeolitic imidazolate framework-8 (ZIF-8), and it is employed as a catalyst for oxygen reduction reaction (ORR). The influences of carbonization temperature and doping densities on electrocatalytic activity for ORR are investigated. Doping densities of the nitrogen and sulfur are varied using various ratios of ZIF-8 to thiourea and optimized for the best performance for ORR. The synthesized carbon-based catalysts are physicochemically characterized by XRD, TGA, BET, SEM, and XPS. The resulting NSDPC materials exhibit enhanced ORR activity compared to pristine ZIF-8 and the samples after carbonization without doping. In addition, it shows excellent tolerance for methanol cross-over and higher cycling stability than those of commercial Pt/C. This improvement in the catalytic activity of NSDPC is attributed to the mesoporous structure and new active sites derived from the introduction of nitrogen and sulfur.

Amine-functionalized graphene was synthesized via a one-step solvothermal method and used as a metal-free cathode for non-aqueous lithium–oxygen batteries. The material delivered an outstanding specific capacity of 19,789 mAh/g at a current density of 200 mA/g as well as better cycling stability than graphene without the amine functional group. This improvement was attributed to the electron-donating effect of the amine groups and appropriate mesopore volume, which can promote the penetration of oxygen, electrons, and lithium ions, as well as accommodate more discharge products, Li2O2 in Li–O2 batteries. Amine-functionalized graphene has an amine functional group on the carbon surface, which improves the electrical conductivity of carbon and provides electrochemical active sites for oxygen absorption reactions.

A practical heterogeneous catalyst was prepared by anchoring a triazine-tethered N-heterocyclic carbene (NHC)–palladium complex on the surface of graphene oxide (GO) nanosheets. The immobilized complex was characterized by X-ray photoelectron spectroscopy, field-emission transmission electron microscopy, energy-dispersive X-ray spectroscopy, and surface area analysis. It proved to be a highly active and durable heterogeneous catalyst for Suzuki coupling reactions. At room temperature, the use of this catalyst enabled the preparation of various biaryls and heterobiaryls in short reaction times. The catalytic system could be recycled at least 10 times with almost consistent activity. The results reveal that the stable palladium complex is strongly anchored on the surface of GO nanosheets. Interestingly, an open planar network of the GO nanosheet support plays a role during the catalytic process in enhancing the catalytic activity.

The aim of this study was to examine the kinetics of polymerization and the properties of polyurethane (PU) synthesized from renewable sources named iPU using isosorbide (ISB), cPU using caster oil (CO), and hPU using the both. The synthesis was carried out via two-step polymerization by varying the contents of CO and ISB. The reaction rate, determined by FTIR, of the bio-based monomers was slower than that of the petroleum-based monomers. The activation energy was calculated from the reaction rate under different conditions. The physicochemical, morphological, and mechanical properties were examined by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), atomic force microscopy (AFM), and universal testing machine (UTM). The weight-average molecular weights (Mw) were in the range of 13,288 to 62,212 g·mol-1, glass transition temperature (Tg) of -30.9 to -33.3 oC, tensile strengths of 1.29 to 14.14 MPa, and elongation at breaks of 28 to 1,358%.

High-level heteroatom, N and S, dual-doped graphene with an improved mesoporous structure was fabricated via facile in situ carbonization and used as metal-free cathode for non-aqueous lithium oxygen batteries. The prepared cathode delivered an ultrahigh specific capacity of 22,252 mAh/g at a current density of 200 mA/g as well as better cycling reversibility because of the larger and copious mesopores, which can promote the penetration of oxygen, electrons, and lithium ions and the ability to accommodate more discharge products, e.g., Li2O2, in Li–O2 batteries. The material had a high level of heteroatom co-doping in the carbon lattice, which enhanced the electrical conductivity and served as active sites for the oxygen reduction reaction.

Over the past decade, advantages of graphene in high-performance gas sensing have been demonstrated, especially for single- or few-layered graphene wherein the theoretical and technical advances are mature. Owing to the complexity of multi-layered graphene (MLG) sensors and the increasing demand for practical applications, there is an urgent need to comprehensively understand the correlation between MLG and its derivatives for developing next-generation gas sensors. Herein, theoretical and empirical strategies for obtaining better gas sensors are developed. These approaches can be divided into three categories: 1) building devices with Fermi level near the Dirac point (EF,Dirac), 2) enhancing the adsorption probability f(x) and driving force (gap between as-prepared and saturated Fermi levels), and 3) accelerating mobility. A device employing p-type reduced graphene oxide (rGO) decorated with n-type indium oxide and phenylenediamine (GIP) was designed and fabricated by adopting approaches 1 and 2 (EF,Dirac and f(x) enhancement). The resulting hole-compensated GIP displayed a remarkable response to formaldehyde (HCHO), which was 66.3 times higher than rGO, with faster response/recovery. GIP also exhibited higher selectivity for HCHO than for ammonia and trimethylamine. We believe that the classification will untangle the complex role of graphene in sensing, helping to design next-generation advanced gas sensors.

Owing to the environmental and economic problems arising from fly ash (FA), there have been various ongoing efforts over the past decades to find a use for it. Among the various applications of FA, its use as a filler in polymer composites has gained much attention. However, most studies have applied FA as a semi-reinforcing filler, which only marginally improves mechanical properties arising from the poor surface wettability of FA with polymer matrices. To solve this problem and to explore new applications, FA was carbonated by bubbling CO2 in water in this study. The carbonated FA was adopted as a fire-proofing filler in silicone rubber (SR). The surface properties and compositional changes of FA by carbonation were thoroughly examined. Mechanical and thermal properties of carbonated FA-filled SR were evaluated. In particular, the gas torch test confirmed that the carbonation of FA increased the penetration time of SR composites by 11%. In addition, the penetration time of the carbonated FA-filled SR composite was 2–3 times greater than that of the composites filled with commercially available fillers.

Pollution emitted from power plants, including a considerable amount of fly ash (FA) and carbon dioxide (CO2), annually increases and is challenging from an environmentally friendly and sustainable point of view. To date, laboratory-scaled approaches cannot efficiently replace the FA-landfilling and mitigate the stress from CO2 emission. Here, a practically operatable fundamental work by combining carbonated FA (C-FA)—immobilizing CO2 in FA—and polypropylene (PP) matrix is reported and reveals abnormal mechanical and thermal features clarified by calculating van der Waals (vdW) interaction from an atomic scale. This is the first study wherein the interaction between instantaneous dipole moment-induced PP and fillers is simulated and examined. The vdW interactions at the (hetero)interfaces are –59.66, –82.30, and −224.39 kJ mol−1 A−2 for PP, calcium oxide (CaO; before carbonation), and calcium carbonate (CaCO3; after carbonation), respectively, which provides concrete theoretical support for interesting findings such as the independence of tensile strength on filler loadings and “well-grown” interface-induced higher conductivity characteristics of the composites. Therefore, this work can offer practical solutions to mitigate pollution, provide a new perspective on fundamental physical interactions, and guide the development of practical next-generation composite materials.

분자량이 다른 세가지의 ethoxylated trimethylolpropane triacrylate를 가교제로 사용한 현탁 중합을 통하여 열팽창 캡슐을 제조하였다. 고분자 쉘은 아크릴로나이트릴과 메타크릴로나이트릴로 구성되었으며 발포제인 아이소옥탄을 캡슐화하였다. 쉘의 가교정도가 증가함에 따라 국부의 가교밀도 차이에 의하여 캡슐의 형태는 구형에서 울퉁불퉁하게 변화하였다. 팽창 특성은 가교제의 종류와 함량에 의해 영향을 받았다. 캡슐의 입경은 가교제의 양이 증가함에 따라 증가하였다. 최적의 가교도를 지닌 ethoxylated (6) trimethylolpropane triacrylate를 사용한 캡슐의 열팽창 특성이 가장 우수하였다.

In this paper, Ti/SnO2-Sb electrodes with different Sb dopant amounts were successfully fabricated on acid-treated Ti substrates by a thermal decomposition method; this was done in an attempt to examine the effect of the doping amount on the electrochemical activity and stability of the electrode. The physicochemical properties of the prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM)-energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The electrochemical properties were investigated by linear sweep voltammetry (LSV), and the stability was studied via accelerated lifetime testing. The electro-catalytic activity of the prepared Ti/SnO2-Sb electrodes was strongly dependent on the amount of the Sb dopant, leading to a change in the OER overpotential. Among the prepared samples, the Ti/SnO2 electrode with 10% of a Sb dopant showed the highest catalytic activity for oxygen evolution reaction (OER), and 87% of COD removal with 20 mA cm−2 of current density for 60 min was achieved in the presence of 10.0 g L−1 of chloride. The findings reported herein suggest that the Ti/SnO2 electrode with an optimized Sb dopant amount shows enhanced electro-catalytic performance by easily generating active hydroxyl radicals, which act as strong oxidizing agents.

Two different heteroatom-doped microporous carbon materials, c-CBAP-N (nitrogen-doped) and c-CBAP-NS (nitrogen/sulfur co-doped), were prepared using a carbonyl-based aromatic porous polymer (CBAP) after amine-functionalization or chemical impregnation, followed by carbonization at 800 °C. The surface areas of c-CBAP-N and c-CBAP-NS were 1060 m2 g−1 and 1047 m2 g−1, respectively, which are predominantly microporous with a uniform pore size distribution centered at 0.4 nm. Their electrochemical performances as supercapacitors were measured by a three-electrode system using a 6 M KOH solution as the electrolyte. The specific capacitances of the c-CBAP-N and c-CBAP-NS electrodes were 203.2 F g−1 and 157.7 F g−1, respectively, as measured by galvanostatic discharge–charge analysis at a current density of 1 A g−1. Notably, these values are significantly higher than that of commercial activated carbon (130 F g−1 at 1 A g−1).

A series of highly microporous carbon materials was produced by carbonization of a triazine-based covalent organic polymer (TCOP) followed by carbonization and CO2 physical activation. The N-containing porous COP was prepared from easily available economic monomer precursors via a simple Friedel-Crafts reaction, which produced a predominantly microporous structure with a high surface area. Carbonization at 600–900 °C produced predominantly microporous carbons with a narrow pore size distribution in the range of 0.5–1.5 nm. Upon further activation using CO2, more micropores were formed, accompanied by an increase in the surface area (to 2003 m2 g−1) and the nitrogen level in the carbon structure was maintained at ca. 2 wt%. The electrochemical properties of the samples were measured by employing a three-electrode system with 6 M KOH electrolyte. Among the prepared carbon samples, the electrode fabricated using the carbon activated at 900 °C (AC-900) had a specific capacitance of 278 F g−1 at a current density of 1 A g−1, which is significantly higher than that of a commercial activated carbon (130 F g−1) and ranks among the highest reported so far. This improved performance was attributed to the highly microporous structure of the nitrogen-doped carbon with a narrow pore size distribution.

We propose a simple method to investigate both the qualitative and quantitative properties of titanium tetrachloride. The selection and concentration of the employed solvent were found to be very important in the analysis of highly reactive titanium tetrachloride (TiCl4). Herein, we employed various concentrations of an acid solution to serve as a stabilizing medium. Qualitative analysis was performed via Fourier transform-infrared spectroscopy (FT-IR) and scanning electron microscope-energy dispersive spectroscopy (SEM-EDS). Additionally, the quantitative analysis was performed via inductively coupled plasma optical emission spectroscopy (ICP-OES). We concluded that both the qualitative and quantitative properties of titanium tetrachloride could be easily measured using a specific acidic solvent as a medium.