Polyacetylene Research Articles

A practical approach to design sulfur host material for lithium-sulfur batteries based on electrical conductivity and pore structure

Lithium-Sulfur (Li–S) batteries have emerged as one of the most promising batteries and as a next-generation energy source owing to their excellent gravimetric energy density. Sulfur is abundant in nature. Carbon materials have been widely used as sulfur host materials owing to their high electrical conductivity and large surface area. As the host materials highly influence the performance of Li–S batteries, their properties should be well designed. Therefore, understanding the significance of the properties of these materials as sulfur hosts is important in the practical design of electrodes. In this study, sulfur composite cathodes were fabricated using acetylene black (AB) and active carbon (AC) to investigate the effect of the carbon host material on the performance of the Li–S batteries. AB has a higher electrical conductivity and a smaller surface area compared to AC. The sulfur composite cathode with AB shows excellent cycling and kinetic performance compared with the sulfur composite cathode with AC, even though AC has a larger surface area, indicating that the cycling and kinetic performance of the Li–S battery is dominantly affected by the electrical conductivity of the carbon host.

Functionalization of carbons for Pt electrocatalyst in PEMFC

One of the limitations of conventional carbon-supported Pt electrocatalyst in Proton Exchange Membrane Fuel cell (PEMFC) is the carbon corrosion during start-up and shut-down of a fuel cell. The present work investigates the stability of three different carbon blacks and their functionalized forms as supports for Pt electrocatalysts. Acetylene black (AB) as a low surface area carbon shows a higher degree of graphitization and effective functionalization than Vulcan carbon and Ketjan black. Electrochemical tests on corrosion studies show that the AB and its functionalized form (f-AB) as support for Pt electrocatalyst exhibits good electrochemical activity with an ECSA of 52 m2g-1 and 78 m2g-1 and excellent corrosion resistance with minimum ECSA loss of 6% and 16% for Pt/AB and Pt/f-AB, respectively, satisfying the DoE target (<40% ECSA loss.) This makes the Pt/f-AB a promising durable electrocatalyst for PEMFC with improved activity and durability.

Thickness Dependence of Resistance Components of a LiNixCoyMn1-x-yO2-Based Positive Electrode for Lithium Ion Batteries

Dependence of charge-transfer resistance (R ct ) on thickness of positive electrodes for high-power lithium-ion batteries (LIBs) was investigated. The results of the investigation show that R ct of a LiNixCoyMn1-x-yO2 (NCM)-based positive electrode is increased by decreasing electrode thickness to less than 15 μm, while R ct of electrodes with thickness greater than 15 μm stayed almost constant. Scanning spreading resistance microscopy indicated that the electronic resistances of thinner electrodes were higher than those of thicker electrodes. Given that result, we consider that the formation of an electrically conductive network in the thinner electrode is insufficient compared to that formed in the thicker electrode. Focused-ion-beam scanning-electron-microscopy observation of an electrode with a higher R ct revealed that acetylene black (AB) as an electron conductor and poly-vinylidene-difluoride binder were agglomerated non-uniformly, and large pores formed among the non-uniform aggregates. Presumably, the non-uniform distribution of aggregates and formation of large pores resulted in an insufficient electrically conductive network between the aggregates, which resulted in increased R ct .

Highly sensitive electrochemical sensor for tyrosine detection using a sub-millimeter electrode

In recent years, small-sized electrodes have drawn widespread attraction in electroanalysis due to high sensitivity, rapid response and low cost. Hereby, a sub-millimeter paste electrode with inner diameter of 0.8 mm was prepared by combining the excellent properties of reduced graphene oxide (rGO) and acetylene black (AB), and the electrochemical behavior of tyrosine (Tyr) on the modified electrode (denoted as rGO/ABPE) was investigated in detail. The electrochemical responses obtained on the sub-millimeter rGO/ABPE were compared with that obtained on a conventional size electrode with diameter of 3 mm. The results showed that the 0.8 mm one has better performance than that of 3 mm. Compared with the paste electrode made of graphite powder, the oxidation peak current of Tyr increased significantly due to the synergistic effect of rGO and AB. Under the optimized experimental conditions, the calibration curve of Tyr showed a linear relationship between 0.1 and 100 μM (R = 0.9995) with good sensitivity of 3.314 μA μM−1 cm−2, and the detection limit was 0.06 μM. By comparison with conventional size electrode, the detection of Tyr on the sub-millimeter electrode shows higher sensitivity, wider linear range and lower detection limit. In addition, the excellent reproducibility, stability and selectivity of the sub-millimeter rGO/ABPE make it suitable for Tyr analysis in both food and biological samples.

Synergetic electrocatalytic degradation of isophorone by active oxygen species generated in the gas diffusion electrode and PbO2 anode

Significant efforts have been made to achieve efficient H2O2 generation via oxygen reduction reaction (ORR). Here, the acetylene black (AB)-based gas diffusion electrodes (GDEs) modified by PTFE were fabricated and applied in a closed autoclave for H2O2 generation for the first time. The surface morphology, BET, XPS, cyclic voltammetry curves and linear scanning voltammetry curves of GDEs were all characterized. Additionally, the H2O2 generation experiments of GDEs and the relationship between H2O2 yield and BET surface area (SBET), double layer capacitance (Cdl) were all investigated. It could be found that the SBET and Cdl of GDEs kept a good linear relationship with H2O2 content, and 2#GDE (AB:PTFE = 1:3) possessed the optimal H2O2 generation capacity. Also, the effect of oxygen pressure and current density on H2O2 production was evaluated detailedly, indicating higher oxygen pressure was beneficial to the H2O2 generation and the preferable current density was 20 mA cm−2 due to the side reactions. And all the H2O2 electro-generation experiments exhibited a higher oxygen utilization efficiency (0.77%–2.93%). Finally, the efficient and synergetic electro-catalytic degradation of isophorone was achieved by self-made PbO2 anode and GDE.

A review on the development of conjugated polymer-based textile thermoelectric generator

Thermoelectric (TE) materials based on conjugated/conductive polymers can directly convert heat into electricity, and thus found promising applications in energy scavenging and cooling technologies. The performance of these thermoelectric materials is governed by different parameters like the nature of the material, thermal stability, electrical conductivity, Seebeck coefficient, and thermal conductivity. Although the traditional inorganic semiconductor materials such as PbTe (Lead Telluride), Bi2Te3 (Bismuth Telluride), SiGe (Silicon-Germanium), SnSe (Tin Selenide), and Skutterudite (CoAs2) are giving high performance, they have some inherent limitations, such as poor processability, toxicity, rare availability, and high cost of manufacturing. Whereas, organic conjugated polymers such as polyacetylene (PA), polyaniline (PANi), Poly(3-hexylthiophene) (P3HT), polypyrrole (PPy), poly 3,4-ethylenedioxythiophene (PEDOT), etc. have low cost of synthesis, light in weight, low toxicity and better processibility. Organic textile thermoelectric generators (T-TEG) can be prepared by in-situ polymerization of the conjugated polymers onto textile substrates. This article reviews the preparation, design and performance of these T-TEGs. Various approaches and scopes of improvement of efficiency of the thermoelectric effect of the T-TEGs are discussed. Various potential applications of the T-TEG in different fields are also described.

Chemical Mesoscopics Notions in the Explanation of Polymeric Materials Modification Mechanism with Participation of Metal Carbon Mesocomposites

The paper is dedicated to the consideration of the chemical mesoscopics notions application for the explanation of polymeric materials modification mechanism by the metal carbon mesoscopic composites. The main peculiarities of these nanosized particles are following: a) the presence of unpaired electrons on the carbon cover; b) the structure of carbon cover consists from poly acetylene and carbine fragments; c) the atomic magnetic moment of inner metal is equaled to more than 1,3 μB. The metal carbon mesocomposites activity depends on the medium and conditions influence because of the possible changes of the phase coherency and quantization of negative charges.

Salt-resistant solar still based on hollow sphere porous ionic polymers for desalination

The exploitation of photothermal materials (PM) with desired salt-resistance is significant importance for solar steam generation (SSG). Herein, a novel salt-resistant PM based on porous ionic polymers（PIPs）coated with acetylene black (AB) was prepared for efficient SSG (named as PIPs-AB). The PIPs were synthesized using alkynylbenzene and ionic monomers as building blocks by Sonogashira-hagihara cross coupling reaction, which show low thermal conductivity (0.1 W m−1 K−1) and super hydrophilicity (infiltration within 40 ms). By decorated with AB, an excellent light absorption of 90% for the as-prepared PIPs-AB was obtained. Coupling with their superior thermal insulation and desired water transportation ability, the as-prepared PIPs-AB exhibits superior solar conversion efficiency (85.4% under 1 sun illumination). Furthermore, the intrinsically ionic feature of PIPs, combining with the Janus structure composed of superhydrophilic PIPs monolith and hydrophobic AB coating, makes the PIPs-AB excellent salt-resistant ability, e.g. no salt accumulation was observed after 6 h duration at 1 sun irradiation. Taking the advantages of the inherently adjustable chemical composition and tunable porosity of PIPs, the results of this work may open an opportunity for rational design and preparation of high-performance PIPs-based PM with desired salt-resistance for real SSG applications.

Is there a Demand of Conducting Agent of Acetylene Black for Graphene-Wrapped Natural Spherical Graphite as Anode Material for Lithium-Ion Batteries?

Is there a Demand of Conducting Agent of Acetylene Black for Graphene-Wrapped Natural Spherical Graphite as Anode Material for Lithium-Ion Batteries?

Metal-carbon mesocomposites application possibilities as the medicine magnetic transport within an organism

The paper is dedicated to the consideration of the metal-carbon mesocomposites application possibilities for the medicine magnetic transport. This trend is determined by correspondent peculiarities of content and structure of mesoscopic composites. The main peculiarities of these nanosized particles are the following: a) the presence of unpaired electrons on the carbon shell; b) the structure of carbon shell from poly acetylene and carbine fragments; c) the atomic magnetic moment of inner metal is equaled to more than 1–3 μB. The creation of reactive mesoscopic materials with regulated magnetic characteristics which can find application as medicine magnetic transport within an organism is very topical. The present investigation has fundamental character. It’s based on the ideas concerning to the change of metal-carbon mesocomposites reactivity. The use is possible as metal-carbon mesocomposites both and they are modified analogously.

All-Solid-State Lithium Battery Using Mg(BH4)2 As an Electrode

All-solid-state batteries are required to show the large capacity and reduce of the interfacial resistance between the solid electrolyte/electrode interface. To address these issues, “complex hydrides” have recently received attention as solid electrolytes for all-solid-state lithium batteries. In this study, we focus on Mg(BH4)2 as conversion-type anode active material for all-solid-state rechargeable lithium batteries. Mg(BH4)2 has been reported as an anode active material for Li-ion battery with 1M LiPF6/EC+DMC(1:1) [1]. However, the reaction mechanism of the Mg(BH4)2 anode is still unclear. There are following 4 types of possible conversion reactions, and the reaction formula (1) and (2) were assumed in Ref. 1.Mg(BH4)2 + 8Li → 8LiH + 2B + Mg (1) ; The theoretical capacity: 3970 mAh/gMg(BH4)2 + 6Li → 6LiH + 2B + MgH2 (2) ; The theoretical capacity: 2978 mAh/gMg(BH4)2 + 4Li → LiBH4 + 3LiH + B + 0.5Mg + 0.5MgH2 (3) ; The theoretical capacity: 1985 mAh/gMg(BH4)2 + 2Li → 2LiBH4 + Mg (4) ; The theoretical capacity: 992 mAh/gHowever, since its initial discharge capacity was less than 700 mAh/g, we inferred that the discharge reaction formula should be formula (4) with the smallest theoretical capacity. In the case of (4), we can expect the formation of LiBH4, which is a Li ion conductor, as a discharge product [2]. In solid-state batteries, it is necessary to include a solid electrolyte of almost the same weight in addition to the active material in the electrodes, which is a major hindrance to the improvement of the energy density of the solid-state battery. However, if Mg(BH4)2 self-generates the ionic conductor LiBH4 according to the reaction formula (4), Mg(BH4)2 anode should be freed from the handicap. In addition, another discharge product, Mg metal, should be useful to reduce the interfacial resistance. To confirm the self-generation effect of LiBH4, we compare the anode performance of Mg(BH4)2 with/without LiBH4;Mg(BH4)2 + LiBH4 + acetylene black (AB) = 40 : 30 : 30 (weight ratio)Mg(BH4)2 + AB = 70 : 30 (weight ratio)The electrodes were mixed by mechanical milling of a mixture of Mg(BH4)2 : AB = 70 : 30 (weight ratio) and / or Mg(BH4)2 : LiBH4 : AB = 40 : 30 : 30 (weight ratio) at 400 rpm under argon atmosphere. Milling was performed using a planetary-type mill (FRITSCH Pulverisette 6). The solid electrolyte LiBH4 and the anode mixture were uniaxially pressed at 10 kN and 30 kN to obtain two-layer pellets, respectively (diameter; 10 mm). The two-layer pellets were pressed against Li metal to form half cells, and discharge/charge measurements were performed using HS cells (Hohsen Corp.). Figure 1 shows discharge/charge curves of anode mixture with/without LiBH4 at 120 oC. From the discharge/charge curves of Figs. 1 (a) and (b), it can be seen that the reversible reaction proceeded even without LiBH4 in the anode electrode mixture. Furthermore, in comparison of the specific capacity based on the total weight of the composite anode including AB, the initial reversible capacity of anode without LiBH4 in Fig. 1 (a) was much larger than that of anode with LiBH4 in Fig. 1 (b). Although there is room for improvement in the utilization of anode without LiBH4, a flat voltage plateau was also observed around 0.8 V with only 0.1 V overvoltage even at 0.5 mA/cm2 high rate condition. These results suggest that the anode self-assembles LiBH4 with high ionic conductivity during the discharge process according to the formula (4), as initially expected. In addition, the cycling performance of the anode without LiBH4 was almost similar to that of the anode with LiBH4 as shown in Figs. 1 (c) and (d). From the result of the ex-situ XRD, it was confirmed that Mg metal was formed in the discharged sample, although the diffraction peak of LiBH4 could not be detected. We will discuss the detail reaction mechanism during the cycling at the presentation.

Factors Affecting on Electrochemical Properties of O3-Type NaFeO2 for Sodium Ion Batteries

LiCoO2 is generally used as a positive electrode material for lithium ion batteries. However, the abundance of cobalt in the Earth’s crust is limited to be less than 100 ppm, and therefore cobalt is expensive element. Iron-based electrode materials would be attractive as positive electrode materials for battery applications because iron is the most abundant transition metal ion. However, as a counterpart of LiCoO2, layered LiFeO2 is electrochemically inactive.[1] In contrast, layered NaFeO2 is electrochemically active, but cyclability is not enough associated with the irreversible structural change upon charge.[2, 3] In this study, we examine different factors affecting the electrode properties of NaFeO2 and discuss possibility as the positive electrode material for sodium ion batteries.O3-type NaFeO2 was prepared by solid-state reaction from stoichiometric amount of Na2O2 and Fe2O3 as described by Takeda et al.[4] These starting materials were mixed using a mortar and pestle in an argon-filled globe box, and then pressed into a pellet. The pellet was heated at 650 oC for 12 h in O2. After the sample was prepared, the sample was mixed with acetylene black (NaFeO2: acetylene black = 90: 10 wt%) by using the planetary ball mill.Figure 1 shows the XRD patterns and SEM images of O3-type NaFeO2 before and after mixing with acetylene black (denoted as as-prepared and carbon-composite NaFeO2, respectively). The as-prepared sample crystallizes into an O3-type layered structure as previously reported, and, from the XRD patterns, no change in the structure is found after milling with carbon. However, the particle size of the sample is clearly reduced by milling with carbon. Charge/discharge curves of O3-type NaFeO2 before and after milling with carbon are compared in Fig 2. A voltage profile of the as-prepared sample with a well-defined voltage plateau at 3.3 V is similar to that of the previous reports, and capacity degradation on electrochemical cycles is clearly observed. In contrast, carbon-composited NaFeO2 delivers a reversible capacity of over 100 mA h g-1 with much improved capacity retention.From these results, we will discuss factors affecting electrode reversibility of O3-type NaFeO2 and possibility of rechargeable batteries made from only abundant elements.

In-Situ EIS to Investigate Effect of C-Rate on Impedance Spectra of Positive Electrodes with Different Ratio of Conductive Additives in Lithium Ion Batteries

Active materials, conductive additives and binders are widely used for the fabrication of positive electrodes of lithium ion batteries (LIBs). The electrochemical performance of positive electrodes is affected by the addition rate of conductive additives on the electrode 1). It is important to investigate the effect of the addition rate of conductive additives on the electrode performance of the positive electrode during charge-discharge cycle in order to develop LIBs that can charge and discharge at high C-rate. In the present study, the in-situ EIS 2) was employed to investigate the effect of C-rate on impedance spectra of positive electrode with different additive rates of conductive additives.The positive electrode with different additive rates of acetylene black (AB) was fabricated by screen printing. The mixture of the slurry containing LiCoO2 powder, AB, polyvinylidene fluoride and N-methylpyrrolidone were screen-printed on the aluminum foil. In the present study, the positive electrode with different additive rates of AB was used for the impedance measurement. The spherical natural graphite fabricated on cupper foil was used as the negative electrode and a lithium wire was used as the reference electrode (RE). All measurements were carried out by the three-electrode cell (Toyo system co. ltd.) at room temperature in an argon atmosphere.The 3D impedance of positive electrode, negative electrode and full cell was measured by in-situ EIS during charge and discharge. In the 3D impedance of positive electrode, three loops were observed on the Nyquist plane during charge and discharge. As the diameter of loop in the low frequency range was decreased with the increase of the state of charge (SOC), this loop may be related to the time constant composed of the charge transfer resistance R ct and the electric double layer capacitance 2). In order to examine the effect of C-rate on impedance of positive electrode, the changes of R ct values during charge and discharge were estimated from the instantaneous impedance at arbitrary SOC on 3D impedance of positive electrode. The relationship between C-rate and additive rates of AB on the impedance of positive electrode was discussed.

Effect of Varying Carbon Supports on Pt Based HOR Electrocatalysts for Alkaline Media Synthesized By CVD

The synthesis of electrocatalysts for the chemical reactions of hydrogen systems (e.g. fuel cells and electrolyzer systems) continues to be a significant area of research in the renewable energy community. The kinetics of hydrogen reactions decrease by two orders of magnitude in alkaline environments compared to acidic, which has rendered significant challenges in the development as catalysts of alkaline fuel cell systems[1,2]. Chemical vapor deposition (CVD) is a conventional synthesis process applied to manufacture electrocatalysts[3,4]. In this study, a modified form known as “Poor Man’s” CVD (PMCVD) is utilized, to further its impact in electrochemical catalyst development. This work assesses the deposition mechanism as well as its ability to develop tuneable catalysts for the hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) for alkaline media.In our last efforts, we showed Pt based catalysts synthesized using the PMCVD method exhibited higher activities for the HOR/HER in alkaline media than commercially available catalysts[5]. The performance was attributed to the tunability of crystallite size by varying the temperature and pressure of the PMCVD process. In an effort to further understand the deposition mechanism of this processes, we investigated Pt catalysts on various carbon supports. In doing so, Pt was deposited on three supports: XC-72, Acetylene Black, and Graphitized Nanoplatelets with 30% Pt by weight. The carbons varied in both surface areas and degree of graphitization. This work will summarize the HOR/HER activities of these three Pt/C catalysts in alkaline media. It will also help elucidate the impact of the deposition mechanism as a function of each support based on their material properties.[1] Durst, J. et al. New insights into the electrochemical hydrogen oxidation and evolution reaction mechanism. Energ. Environ. Sci. 7, 2255–2260 (2014).[2] Sheng, W. et al. Hydrogen Oxidation and Evolution Reaction Kinetics on Platinum: Acid vs Alkaline Electrolytes.” Electrochem. Soc. 2010 volume 157, issue 11, B1529-B1536[3] Garcia, Vargas, et al., “Chemical Vapor Deposition of Iridium, platinum, Rhodium, and Palladium.” Materials Transactions, Vol. 44, No. 9 (2003) pp. 1717 to 1728[4] Serp, Philppe, et. al., “Chemical Vapor Deposition Methods for the Controlled Preparation of Supported Catalytic Materials.” Chem. Rev. 2002, 102, 3085−3128[5] Williams, S. et. al. “Synthesis and Characterization of Electrocatalysts for the Hydrogen Evolution Reaction in Alkaline Environment.” ECS Fall 2019. Figure 1

An Aqueous Symmetrical Sodium-Ion Battery Using New Concentrated Sodium Trifluoroacetate Electrolyte

Aqueous Na-ion batteries have gained increasing attention as alternative devices to conventional non-aqueous Li-ion batteries for larger-scale energy storage, because they face formidable problems on manufacturing cost, rate capability, and safety. Although thermodynamic theoretical electrochemical window of water (1.23 V) has imposed a restriction on aqueous batteries in the selection of cathode and anode active materials, recent studies have revealed that some highly concentrated electrolytes effectively prevent electrochemical decomposition of water, and that a judicious choice of electrode active materials with flat potential plateaus within the range of a kinetic practical electrochemical window successfully leads to the expansion of working voltage in aqueous cell [1-3]. Nevertheless, the solute for reported highly concentrated electrolytes has been limited to either highly expensive perfluoroalkylsulfonylates or perchlorates that require special care in handling under dry condition. We have explored more beneficial solutes that contribute in the reduction of manufacturing cost and found that a concentrated aqueous solution of NaCO2CF3 (NaTFA, sodium trifluoroacetate) serves as a suitable electrolyte when NASICON-type Na2VTi(PO4)3 (NVTP) is employed both as cathode (V3+/V4+) and anode (Ti4+/Ti3+ and V3+/V2+). Herein we discuss on the symmetrical operation of NVTP with very flat plateaus in this aqueous Na-ion battery, whose capacity retention is highly dependent on the choice of electrolytes.Our initial study focused on the electrochemical performance of Na3V2(PO4)3 (NVP) and NVTP as an electrode in the symmetrical cell using 26 mol/kg (m) NaTFA aqueous electrolyte. NVP and NVTP were prepared by conventional solid-state reaction at 900℃ for 24 h under Ar + H2 atmosphere. The cathode/anode disk pellets were fabricated with acetylene black (AB) as a conductive additive and polytetrafluoroethylene (PTFE) as a binder in a weight ratio of active material/AB/PTFE = 70/25/5, respectively, and then sandwiched by titanium (Ti) or aluminum (Al) mesh as a current collector. As is clear from Figures 1a and 1b, NVTP//NVTP was superior to NVP//NVP in terms of overpotential. Another point to note is the reversible and 2 flat plateaus observed with NVTP//NVTP. These notable differences may arise from the marked robustness, insolubility and ionic conductivity of NVTP, which indicates the importance of partial substitution of V in NVP with Ti.Next, we identified the importance of 26 m NaTFA aqueous electrolyte by comparing it with other representative highly concentrated aqueous electrolytes under otherwise identical conditions. Figure 1c illustrates the capacity retentions of NVTP//NVTP symmetrical full cells when 17 m NaClO4 (purple) and 26 m NaTFA (green) were used as an electrolyte. The purple lines declined prominently in earlier cycles and the dissipated capacity after 50 cycles reached to 10 mAh/g. By contrast, the green line was reluctant to decline even after 300 cycles. We believe that 26 m NaTFA may form anion-derived SEI on the anode, which could possibly suppress reductive decomposition of water.AcknowledgementThis work was supported by Element Strategy Initiative of MEXT, Grant Number JPMXP0112101003.

Synthesis and Electrochemical Properties of β-LiVOPO4/C as Cathode Materials for Lithium-Ion Batteries

Abstract Due to the high theoretical capacity, high platform voltage, stable structure, and mild conditions for synthesis, LiVOPO4 is expected to become the next generation of cathode materials for lithium-ion batteries (LIBs). However, due to the relatively weak ionic conductivity, its commercial application has been largely limited. The paper reported that acetylene black was used as the reducing agent and the pure phase nanostructured orthorhombic β-LiVOPO4 was obtained by carbothermal reduction method. A significant improvement in ionic conductivity was achieved, and the results were compared with previous studies, the initial discharge capacity of the material was considerably enhanced. The results show that the electrical conductivity and the initial discharge capacity of the material were also significantly improved. The sample obtained by holding at 600 °C for 10 h exhibited a maximum discharge capacity of 141.4 mAh g−1 between 3 V and 4.5 V at 0.05 C, with a value of 136.3 mAh g−1, retained after 50 cycles. This represents capacity retention of 96.39%.

Two new pseudo-isomeric nickel (II) metal–organic frameworks with efficient electrocatalytic activity toward methanol oxidation

Searching for non-noble metal catalysts with high activities and low price is critical to the commercialization of methanol oxidation in the process of fuel cells. Herein, two new pseudo-isomeric Ni metal–organic frameworks (Ni-MOFs) (CTGU-17/CTGU-18) have been prepared with 1,4-naphthalenedi-carboxylate (H2NDC), 4,4′-dipyridyl amine (DPA) and Ni(ClO4)2 under hydrothermal condition. Each phase contains one water molecule, but differs dramatically in its bonding to the framework, resulting in different topological networks with fourfold interpenetrating 4-connected dia net (CTGU-17) and (3,7)-connected net (CTGU-18) and diverse electrocatalytic performance for methanol oxidation reaction (MOR). Remarkably, by combining each MOF with the conductive additive, acetylene black (AB), a composite material, AB&CTGU-18(2:4) was confirmed to have an excellent performance for MOR with a high mass specific peak current of 442.3 mA·mg−1. The enhanced electrocatalytic activities and robustness might be attributed to the synergetic effect of acetylene black and the active metal centers of MOFs particles for methanol oxidation. The present work would provide a new insight for the rational design of MOFs-based composites with enhanced methanol oxidation reaction performance.

Increasing Electrical Conductivity of Free-Standing Sulfurized Polyacrylonitrile Cathode for Lithium–Sulfur Batteries

Sulfurized polyacrylonitrile (S-PAN) is one of the best materials for addressing some of the intrinsic drawbacks of lithium–sulfur batteries, such as the intrinsic insulating properties of sulfur and the shuttle phenomenon. Moreover, while S-PAN nanofiber composites are flexible, they still presents shortcomings, such as low rate capability, which is due to their semiconductor electrical conductivity. In this study, we prepared S-PAN webs with high electrical conductivity via electrospinning using conducting agents. Additionally, we analyzed the electrochemical properties of the S-PAN webs prepared using various conducting agents (acetylene black, Ketjen black, and multi-walled carbon nanotubes). The specific capacity of the S-PAN web prepared using acetylene black was 740 mAh g–1 at the charge rate of 5 C. The excellent rate capability of S-PAN prepared using acetylene black was attributed to its low electrical resistance and low charge transfer resistance.

Linear response of the indirect J‐coupling alternation to the energy gap of increasing π‐conjugated oligomers

AbstractWe have investigated the dependence of the electronic energy gap of organic conjugated oligomers on the J‐coupling alternation (JCA) parameter, derived from the nuclear magnetic resonance (NMR) spectroscopy. We exploit the systematic and concerted oscillations observed for the indirect spin‐spin coupling constants (SSCCs), between two adjacent 13C nuclei (1JCC), in the π‐conjugated systems. Hence, we define a scalar JCA parameter in terms of the differences of 1JCC, which is further analyzed as a function of the HOMO‐LUMO gaps (the energy difference between the frontier molecular orbitals), as well as other properties of the studied oligomers. Using an adequate exchange‐correlation density functional approach, we show that, for all systems considered here, that is, polyacetylene (PA), poly(para‐phenylene) (PPP), polypyrrole (PPy), and polythiophene (PTh), their calculated electronic energy gaps may exhibit a linear dependence on the JCA. Our results indicate that a single‐valued NMR‐based parameter properly renders the electronic features of highly conjugated oligomers, allowing us to compare the strengths of J‐couplings in different systems. The present description yields a way to capture both the bonding features and the electronic absorption of these systems provided by the SSCCs. The JCA gives evidence for the differences in the electronic structure of distinct classes of conjugated systems, such as PA, and those that can exhibit a quinoid character, such as PPP, PPy, and PTh.

Application of synthesized porous graphitic carbon nitride and it's composite as excellent electrocatalysts in microbial fuel cell

The performance of microbial fuel cells (MFCs) consisting of exfoliated porous graphitic carbon nitride (ep-GCN) and its composite with acetylene black (AB) as cathode catalyst is evaluated. The cyclic voltammetry and electrochemical impedance spectroscopy of composite ep-GCN-AB indicated excellent oxygen reduction reaction activity and comparable charge transfer resistance with respect to Pt–C. The absence of X-ray diffraction peak at 2θ = 13° (corresponding to stacked structure of bulk GCN) indicated reduction in thickness. Four MFCs were operated with simulated wastewater with chemical oxygen demand (COD) of 3000 mg L−1. The maximum power densities of MFC-GAB (14.74 ± 0.17 W m−3), MFC-PAB (15.68 ± 0.58 W m−3) and MFC-G (12.47 ± 0.30 W m−3) using ep-GCN-AB, Pt–C and ep-GCN electrocatalyst, respectively, were 2.6, 2.7 and 2.2 times higher than MFC-AB operated with only acetylene black coated cathode. The investigation demonstrates that ep-GCN and its composites can be utilized as excellent cathode catalysts in MFCs at 20 folds lesser cost than Pt–C.