Flexible supercapacitors (SCs) with compact configuration are ideal energy storage devices for portable electronics, owing to their original advantages (e.g., fast charging/discharging). To effectively reduce the volume of SCs, an integrated electrode of free-standing polyaniline (PANI)/single-wall carbon nanotube (SWCNT) film with high performance has been developed via a facile solution deposition method, which can be employed as current collector and active material in the meantime. Thanks to the strong π–π interactions between PANI and CNTs, an efficient conductive network with ordered PANI molecular chains is formed in this hybrid film electrode, which is beneficial for the ion diffusion process and fast redox reaction resulting in a high capacitance of 446 F g–1 and outstanding cycling stability, achieving 98% retention over 13 000 cycles. Predictably, solid-state SCs constructed by this free-standing PANI/SWCNT film electrode exhibited remarkable mechanical stability and flexibility in a compact configuration, let alone its excellent capacitive performance (218 F g–1). Moreover, the highest energy density of flexible solid-state SC reached 19.45 Wh kg–1 at a power density of 320.5 W kg–1, further indicating a good potential as an energy storage device. This work would inspire other simple process techniques for high-performance flexible SCs, catering to the demand of portable electronic devices.Keywords: continuous conductive network; free-standing; PANI/SWCNTs; supercapacitor; π−π interactions;

One-dimensional (1D) anisotropic platinum-based nanowires are promising electrocatalysts in polymer electrolyte membrane fuel cells owing to the inherent structural merits. Herein, we report an in situ growth of ultrathin PtRh nanowires (diameters of 2–3 nm) on graphene nanosheets via the oriented attachment pathway. Mechanistic studies reveal that graphene nanosheets play a critical role in the nucleation and growth of PtRh nanowires. The resulting hybrid of PtRh nanowire decorated graphene nanosheets shows outstanding activity and durability toward ethanol electro-oxidation. It exhibits a specific current density of 2.8 mA cm–2 and a mass-normalized current density of 1 A mg–1 metal, which are 5.4 and 3.1 times those of the state-of-the-art Pt/C catalyst, respectively. After 2000 cyclic tests, it maintains 86% of the initial electrochemically active surface area, which is larger than that of 63% obtained from the Pt/C catalyst. The superior performance is attributed to the combination of the advantageous 1D morphological motif with the synergistic effects of PtRh alloys and graphene nanosheet support.Keywords: ethanol electro-oxidation; graphene nanosheets; graphene-mediated synthesis; polymer electrolyte membrane fuel cells; PtRh nanowires;

A new strategy for the synthesis of luminescent copper nanoclusters (Cu NCs), by virtue of the reduction of Cu2+ using ascorbic acid and the protection of polyvinylpyrrolidone at 75 °C, was reported. Blue emitting Cu NCs with photoluminescence (PL) quantum yield of 12% and high stability up to at least 1 month were obtained. Moreover, the PL of Cu NCs showed a reversible response to temperature, and a linear relationship between PL intensity and temperature even after 10 cycles of repeated heating and cooling process was obtained, indicating great potential application in thermal sensors.

A variety of N-hydrogenated/N-methylated pyridinium salts are elaborately designed and synthesized. Thermogravimetric and X-ray photoelectron spectra analysis indicate the intensities of the NH covalent bonds are strengthened step-by-step from 3,3′-(5′-(3-(pyridin-3-yl)phenyl)-[1,1′:3′,1″-terphenyl]-3,3″-diyl)dipyridine (Tm)-HCl to Tm-HBr and then Tm-TfOH, which results in gradually improved cathode interfacial modification abilities. The larger dipole moments of N+H containing moieties compared to those of the N+CH3 endow them with more preferable interfacial modification abilities. Electron paramagnetic resonance signals reveal the existence of radical anions in the solid state of Tm-TfOH, which enables its self-doping property and high electron mobility up to 1.67 × 10−3 cm2 V−1 s−1. Using the Tm-TfOH as the cathode interfacial layers (CILs), the phenyl-substituted poly(para-phenylene vinylene)-based all-solution-processed polymer light-emitting diodes (PLEDs) achieve more preferable device performances than the poly[(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)]-based ones, i.e., high current density of nearly 300 mA cm−2, very high luminance over 15 000 cd m−2 at a low bias of 5 V. Remarkably, the thickness of the CILs has little impact on the device performance and high efficiencies are maintained even at thicknesses up to 85 nm, which is barely realized in PLEDs with small-molecule-based electron transporting layers.

•A series of cross-linked SPI membranes were successfully synthesized.•The cross-linkable membranes can be reprocessed during film formation.•The cross-linked membranes exhibit improved comprehensive performance.•The resulting membranes show remarkable power density in the DMFC.Cross-linked sulfonated polyimides are one of the most promising materials for proton exchange membrane (PEM) applications. However, these cross-linked membranes are difficult to reprocess because they are insoluble. In this study, a series of cross-linkable sulfonated polyimides with flexible pendant alkyl side chains containing trimethoxysilyl groups is successfully synthesized. The cross-linkable polymers are highly soluble in common solvents and can be used to prepare tough and smooth films. Before the cross-linking reaction is complete, the membranes can be reprocessed, and the recovery rate of the prepared films falls within an acceptable range. The cross-linked membranes are obtained rapidly when the cross-linkable membranes are immersed in an acid solution, yielding a cross-linking density of the gel fraction of greater than 90%. The cross-linked membranes exhibit high proton conductivities and tensile strengths under hydrous conditions. Compared with those of pristine membranes, the oxidative and hydrolytic stabilities of the cross-linked membranes are significantly higher. The CSPI-70 membrane shows considerable power density in a direct methanol fuel cell (DMFC) test. All of these results suggest that the prepared cross-linked membranes have great potential for applications in proton exchange membrane fuel cells.

•The fluorescent flavonoid dye with aggregation-induced emission enhancement characteristic was firstly reported.•The photophysical properties of fluorescent dyes including solvatochromism, AIEE, and photostability were carefully studied.•The fluorescent nanodots based on AIEE flavonoid dyes were fabricated and applied for long-term cell imaging.Fluorescent organic nanodots are considered as the promising tools for long-term cellular imaging, due to their high luminescence, good photostability and good biocompatibility. In this study, a novel triphenylamine-based flavonoid dye with aggregation-induced emission enhancement characteristics was designed and synthesized. Based on these flavonoid dyes, the organic nanodots were facilely fabricated without further surface modification, exhibiting the low cytotoxicity, good resistance against photobleaching, and acceptable cell uptake. Remarkably, these nanodots achieved a long-term bioimaging for living cells with 70% of their initial fluorescence retained after 48 h continuously incubation. The excellent properties made the flavonoid dye the promising addition to the current library of fluorescent organic nanodots in bioimaging application.Download high-res image (253KB)Download full-size image

•A novel highly emissive donor-acceptor flavonoid chemosensor was designed and successfully synthesized.•The chemosensor achieved a fast and sensitive fluorescence response towards nitroaromatics, especially for picric acid in water samples.•The sensing mechanism was studied via DFT calculation and NMR technique, suggesting the emission quenching may result from the photo-induced electron transfer between sensor molecule and picric acid.Direct detection of picric acid in water samples is very important for social security and environmental protection. Herein, a novel donor-acceptor type fluorophore 3-(benzyloxy)-2-(4-(di-p-tolylamino)phenyl)-4H-chromen-4-one has been designed, and synthesized. Due to its aggregation-induced emission enhancement characteristic, this fluorophore showed a very strong fluorescence in water. This fluorophore was then employed as highly sensitive chemosensor for picric acid, with a limit of detection of 370 nM in water. Moreover, this sensor showed very high selectivity towards picric acid among interfering nitroaromatics. At last, the sensing mechanism was carefully studied by using DFT computation and NMR spectra. This work provided a practical and reliable detection method for picric acid in water samples.Download high-res image (287KB)Download full-size image

Benzodithiophene (BDT)-based conjugated polymers have garnered considerable interest due to their planar backbones and improved carrier mobility, and have found wide application in organic field-effect transistors and organic photovoltaics. However, there are few reports on the use of these conjugated polymers as thermoelectric materials. In this work, the conjugated polymer poly(benzo[1,2-b:4,5-b’]dithiophene-alt-3,4-ethylenedioxythiophene) (PBDT-EDOT) was synthesized to investigate the thermoelectric behavior of its composite films with single-walled carbon nanotubes (SWCNTs). The polymer was characterized by 1H NMR, gel permeation chromatography, thermal gravimetric analysis and differential scanning calorimetry. The thermoelectric properties, carrier concentration and mobility of the composite films were also measured. It was found that the composite with an SWCNT content of 30% exhibited a high Seebeck coefficient of 82.1 μV K−1 at room temperature. Additionally, for composites with SWCNT contents below 90%, the power factors reached the highest values at the glass transition point of PBDT-EDOT in the temperature range of 300–400 K.

Synthesis of poly(arylene ether ketone)s containing alkylsulfonated side chains (SPAEKs) has continued in recent years because of their numerous advantages when used as proton exchange membranes (PEMs). Although the oxidative stabilities of SPAEKs have been widely characterized in Fenton's reagent, few investigations have reported the oxidative degradation of the membranes, which is critical to the durability of PEMs. In this work, the oxidative degradation of SPAEKs was carefully studied through analysis of the proton conductivity, 1H NMR and FT-IR spectra, elemental composition, molecular weight (Mw), thermal properties, and morphology in a simulated fuel cell environment. The oxidative degradation was mainly ascribed to the cleavage of the main polymer chain, and the excellent properties of the membrane were maintained before it began to break into pieces.

Three donor–acceptor (D–A)-structured conjugated polymers with different backbones, poly((9,9-dioctylfluorene)-2,7-diyl-alt-benzothiadiazole) (F8BT), poly((9,9-dioctylfluorene)-2,7-diyl-alt-(4,7-bis(3-hexylthien-5-yl)-2,1,3-benzothiadiazole)-2′,2′′-diyl) (F8TBT), and poly(N-9′-heptadecanyl-2,7-carbazole-alt-(4,7-bis(3-hexylthien-5-yl)-2,1,3-benzothiadiazole)-2′,2′′-diyl) (C8TBT), were synthesized via conventional Suzuki polymerization. All three polymers showed good thermal and electrochemical stabilities. The UV-vis absorption spectra indicated that the introduction of thiophene units into the polymer backbone decreased the bandgap of the polymers. When the three polymer films were doped with FeCl3, different thermoelectric properties were observed. F8TBT and C8TBT, which contained thiophene units, showed a higher electrical conductivity than F8BT. As the temperature increased, C8TBT exhibited the highest Seebeck coefficient of 335 μV K−1 at 90 °C and a maximum power factor of 13.11 μW m−1 K−2. These results demonstrated that the polymer backbone structure greatly influences the thermoelectric properties and the inclusion of thiophene and carbazole units can effectively improve the thermoelectric properties. Therefore, this work is a novel and important reference to design and synthesize high-performance thermoelectric conjugated polymers.

Highly branched polymers applied as low-temperature proton exchange membranes (LTPEMs) have attracted attention from researchers because of their outstanding properties. However, there are few reports on the use of branched polymers as high-temperature proton exchange membranes (HTPEMs). In this work, a series of highly branched polybenzimidazoles (PBIs) with 1,3,5-tri(4-carboxyphenoxy)benzene (B3) as a branching agent were designed and successfully synthesized for the first time. The highly branched PBIs were soluble in polar organic solvents and could be cast to form tough and smooth films. Compared with linear PBI membranes, the branched PBI membranes with a 9% degree of branching exhibited a high phosphoric acid (PA) doping level of 10.5 (PA molecules per repeat unit), high proton conductivity (0.043 S cm−1) at 180 °C under anhydrous conditions, high resistance to oxidation and good PA retention ability. All these properties indicate that branched PBI membranes are promising for HTPEMs and can be potentially used in HTPEM fuel cells.

Comb-shaped sulfonated poly(arylene ether)s exhibit excellent properties when applied in proton exchange membranes (PEMs). However, few investigations have reported the use of comb-shaped sulfonated polymers with highly branched backbones as PEMs. In this work, a series of highly branched sulfonated poly(arylene ether)s with flexible alkylsulfonated side chains were successfully synthesized for the first time. The branched polymers were soluble in polar organic solvents and could be cast to form tough and smooth films. The membranes exhibited good overall properties as PEMs. With an increasing degree of branching (DB) value, properties such as oxidative stability, proton conductivity and swelling ratio of the membranes were significantly improved. The membrane with the highest DB value (8%) exhibits high proton conductivity (0.33 S cm−1 at 80 °C) and excellent oxidative stability (445 min) as well as acceptable mechanical properties (20.51 MPa), which indicate that this material is a good candidate PEM for evaluation in fuel cell applications.

Branched sulfonated poly(arylene ether ketone)s (BSPAEKs) exhibit excellent oxidative stability and solubility, making them suitable for proton exchange membranes (PEMs). However, the mechanical properties of branched membranes cannot fully satisfy the requirements of PEMs. In this work, BSPAEK/polytetrafluoroethylene (PTFE) composite membranes are prepared by casting a BSPAEK solution onto porous PTFE films that contain different concentrations of Triton surfactant to reinforce their mechanical properties. The properties of the composite membranes, including their mechanical properties, proton conductivities, oxidative stabilities, water uptake, thermal stabilities and swelling ratios, are investigated experimentally. The tensile strength of BSPAEK/PTFE-7 (7 wt% Triton as a surfactant) is 26.0 MPa, which is 2.1 times higher than that of a pristine membrane. In addition, the BSPAEK/PTFE composite membranes exhibit excellent dimensional and oxidative stabilities. The BSPAEK/PTFE-5 (5 wt% Triton as a surfactant) composite membrane is tested in a direct methanol fuel cell (DMFC), and it can yield a peak power density of 69.70 mW cm−2 at 60 °C, which is somewhat comparable to those using Nafion membranes.

Three kinds of sulfonated poly(ether ether ketone) (SPEEK)/nano oxide (Al2O3, SiO2, and TiO2) composite membranes are fabricated for vanadium redox flow battery (VRFB) application. The composite membranes with 5 wt% of Al2O3, SiO2, and TiO2 (S/A-5 %, S/S-5 %, and S/T-5 %) exhibit excellent cell performance in VRFB. Incorporation of nano oxides (Al2O3, SiO2, and TiO2) in SPEEK membrane improves in aspect of thermal, mechanical, and chemical stabilities due to the hydrogen bonds’ interaction between SPEEK matrix and nano oxides. The energy efficiencies (EEs) of composite membranes are higher than that of Nafion 117 membrane, owing to the good balance between proton conductivity and vanadium ion permeability. The discharge–capacity retentions of composite membranes also overwhelm that of Nafion 117 membrane after 200 cycles, indicating their good stability in VRFB system. These low-cost SPEEK/nano oxide composite membranes exhibit great potential for the application in VRFB.

Highly branched sulfonated poly(arylene ether ketone)s (BSPAEKs) exhibit excellent potential as proton exchange membranes (PEMs). However, the mechanical properties of the branched membranes must be further improved. In this work, a series of BSPAEK-based composite membranes containing different amounts of polyacrylonitrile (PAN) were fabricated as PEMs. The expected ionic cross-linking and hydrogen bonding between BSPAEK and PAN was confirmed by Fourier transform infrared spectroscopy. The tensile strengths of the composite membranes with PAN contents from 5 to 20 % ranged from 16.4 to 23.0 MPa, which were notably higher than that of the BSPAEK membrane (13.1 MPa). Furthermore, the oxidative stability of the composite membranes was enhanced significantly from 295 to 430 min (2 ppm FeSO4 in 3 % H2O2) with increased PAN doping. Although the proton conductivity of the composite membrane was lower than that of BSPAEK, the proton conductivity of the composite membranes was still above 10−2 S cm−1 and satisfied the requirement of the fuel cells. The results indicate that this material is a suitable candidate PEM for evaluation in fuel cell applications.

•A fluorescent bioprobe for copper detection based on flavonoid was firstly reported.•This bioprobe shows a good sensitivity and selectivity toward copper ions, and its copper complex achieves secondary sensing for pyrophosphate.•This bioprobe exhibits a great biocompatibility, enabling recognition of copper ions and pyrophosphate in living cells.Copper is a trace metal nutrient essential for most forms of life. The dysregulation of copper homeostasis is associated with various diseases, such as Menkes disease, Alzheimer's disease, Wilson disease, gastrointestinal disorders, and kidney damage. Therefore, detection of copper ions in biological system is of great significance for fundamental study in biology and medicine field. To address this critical need, we herein developed a novel flavonoid-based bioprobe 6-(bis(pyridin-2-ylmethyl)amino)-2-(4-(dimethylamino)phenyl)-3-methoxy-4H-chromen-4-one (DPA-FL) for copper detection. The DPA-FL showed highly fluorescent response towards copper ions with a high tolerance of other competitive metal ions. The fluorescence intensity at 510 nm are linearly proportional to the amount of Cu2+ from 0 to 10 μM with a detection limit lower than 100 nM (S/N rule). The intracellular recognition of copper ions was successfully achieved in HUVECs. Furthermore, the DPA-FL-Cu2+ complex could also be used for secondary sensing of pyrophosphate in living cells, thus providing a powerful imaging tool for tracking of copper ions and pyrophosphate in biological system.

Silver nanowires have attracted wide research attention for their excellent optical, electrical and chemical properties. Many researches were performed toward synthesizing and application of silver nanowires. The application of silver nanowires such as transparent conductive film electrode, conductive silver adhesive and nanowelding technology was introduced herein. Principles and characteristics of different synthesizing methods of silver nanowires were reviewed in this paper, including template method, liquid polyol method, self-assembly method, ultrasonic reduction method and wet chemical method. The liquid polyol method was the most available one to achieve efficient large-scale production.

As representative conjugated polymers, the physical properties, such as electric conductivity and electro-optic properties, of poly-Schiff bases (PSBs) have been widely investigated. However, to date, the thermoelectric (TE) properties of PSB or related polymers remain unreported. In this study, PSB with a donor–acceptor structure (PSB(A)) was synthesized and was blended with different fillers to prepare polymer–inorganic TE composites. For comparison, PSB with the common structure (PSB(B)) was also synthesized, and PSB(B)–graphite composites were fabricated. The PSB(A)/graphite composites exhibited a higher power factor of 10.2 μW m−1 K−2 compared with 4.5 μW m−1 K−2 of the PSB(B)/graphite composites at the same doping level. The effects of different fillers on the TE properties of the PSB(A)-based composites were investigated in detail, and the highest TE figure of merit, ZT = 2.53 × 10−3, was obtained. The results show that excellent TE materials could be produced by preparing polymer–inorganic TE composites using novel conducting polymers with a special structure (e.g., donor–acceptor structure) and conducting fillers.

•Two types of highly branched star-shaped sulfonated block polymers were synthesized.•The star-shaped block polymers exhibit better properties than the random polymer.•The membranes exhibit considerable proton conductivity and oxidative stability.•The microstructure of the membranes was investigated by SEM and AFM.Star-shaped sulfonated block copoly(ether ketone)s exhibit excellent properties for use as proton exchange membranes (PEMs). However, very few investigations of the use of highly branched star-shaped sulfonated block polymers as PEMs have been reported. In this work, two types of highly branched star-shaped sulfonated block poly(arylene ether)s with 6% branching agent were synthesized via direct polycondensation reactions of a trifunctional core (branching agent) with sulfonated 4,4′-difluorobenzophenone, bisphenol fluorene, and 4,4′-difluorodiphenyl sulfone. The properties of a polymer with hydrophilic segments surrounded by hydrophobic segments (P1) and a polymer with hydrophobic segments surrounded by hydrophilic segments (P2) were investigated. The block polymer P1 exhibited better oxidative stability (332 min) and dimensional stability (<12%) than the highly branched sulfonated random polymer (P3), whereas P2 exhibited higher proton conductivity (0.40 S cm−1 at 80 °C) and water uptake (59.1% at 80 °C) than P3. The highly branched star-shaped sulfonated block poly(arylene ether)s exhibit greater potential than P3 for use as PEMs.

•Highly branched sulfonated poly (fluorenyl ether ketone sulfone)s (HSPAEK) are synthesized.•The HSPAEK with 8% degree of branching is selected.•HAPSEK membrane shows smooth, dense and tough morphology.•It possesses low vanadium ion permeability and high ion selectivity compared to Nafion.•HSPAEK membrane exhibits high efficiency and stability in vanadium redox flow battery.A series of highly branched sulfonated poly (fluorenyl ether ketone sulfone)s (HSPAEK) are synthesized by direct polycondensation reactions. The HSPAEK with 8% degree of branching is further investigated as membrane for vanadium redox flow battery (VRFB). The HSPAEK membrane prepared by solution casting method exhibits smooth, dense and tough morphology. It possesses very low VO2+ permeability and high ion selectivity compared to those of Nafion 117 membrane. When applied to VRFB, this novel membrane shows higher coulombic efficiency (CE, 99%) and energy efficiency (EE, 84%) than Nafion 117 membrane (CE, 92% and EE, 78%) at current density of 80 mA cm−2. Besides, the HSPAEK membrane shows super stable CE and EE as well as excellent discharge capacity retention (83%) during 100 cycles life test. After being soaked in 1.5 mol L−1 VO2+ solution for 21 days, the weight loss of HSPAEK membrane and the amount of VO2+ reduced from VO2+ are only 0.26% and 0.7%, respectively, indicating the superior chemical stability of the membrane.

Recently, the use of polymers as thermoelectric materials has attracted considerable attention. However, relatively few studies have investigated the effects of polymer structures on the corresponding thermoelectric properties of the polymers. In this work, a series of poly(3-methylthiophene methine)s (PMMs) were synthesized for use as thermoelectric materials, and the effects on the Seebeck coefficient of donor or acceptor side groups at the methine carbon were studied. The PMMs with strongly electron-withdrawing and electron-donating groups exhibited the highest Seebeck coefficients. Motivated by the high Seebeck coefficients of the selected PMMs, PMM/graphite composites were prepared via solution mixing followed by mechanical ball milling and cold pressing. The thermoelectric properties of the composites were investigated as a function of the graphite (G) concentration. The highest ZT (6.23 × 10−3) was measured for the poly[(3-methylthiophene-2,5-diyl) (p-(methoxy)benzylidene)]/G composite that contained 90 wt% G. The results of this work suggest that the thermoelectric properties of polymer-inorganic composites can be improved by designing polymers with high Seebeck coefficients.

•The branched polymer with 10% branching agent was synthesized.•The membrane exhibits considerable proton conductivity and oxidative stability.•A2 with hindrance and B3 with long and hard arms can increase degree of branching.•The microstructure of the branched membrane was investigated by SEM and AFM.Branched sulfonated polymers exhibit excellent properties as proton exchange membranes (PEMs). However, very few highly branched sulfonated polymers are reported as PEMs. The highly branched polymer, including the method to increase degree of branching (DB) and the effects of DB on the properties of PEMs, should be further studied. In this work, novel branched sulfonated poly(fluorenyl ether ketone sulfone)s with different DB value are synthesized by direct polycondensation reactions from bisphenol fluorene (A2), sulfonated 4,4′-difluorobenzphenone, 1,3,5-tris(4-(4-fluorophenylsulfonyl)phenyl)benzene (B3-3) and 4,4′-difluorodiphenyl sulfone. The highest DB with 10% branching agent is obtained using the B3-3 monomer. The method to increase the DB is discussed. It is found that B3 scaffold with long and hard arms can effectively increase the DB value. The effects of DB on the properties, including oxidative stability, proton conductivity, water uptake, swelling ratio, thermal stability, mechanical property and microstructure, are investigated. With increasing DB value, oxidative stability and proton conductivity of the membranes increase remarkably, but swelling ratio and tensile strength decrease slowly. The membrane with the highest DB value (10%) exhibits high proton conductivity (0.42 S cm−1) and oxidative stability (327 min), as well as relatively low swelling ratio (16.2%) at 80 °C.

•The composites prepared by solution mixing showed the best thermoelectric properties.•The Seebeck coefficient slightly fluctuates with increasing MWNT content.•The electrical conductivity increases remarkably with increasing MWNT content.•The highest ZT of 8.71 × 10−4 was obtained with 80 wt.% MWNT.Different polythiophene (PTh)/multiwall carbon nanotube (MWNT) composites with 30 wt.% and 50 wt.% MWNT were prepared by mechanical ball milling, solution mixing and in situ composite, respectively. The composites prepared by solution mixing showed the best thermoelectric properties among these methods. Therefore, the morphology, internal structure and thermal stability of the composites by solution mixing were evaluated by SEM, XRD, FTIR and TGA. The results showed that the MWNT were uniformly dispersed in the polymer matrix and the composite materials exhibited good thermal stability under 200 °C. The effect of MWNT content in the composites on thermoelectric properties, such as electrical conductivity, Seebeck coefficient and thermal conductivity were investigated. With increasing MWNT content, the Seebeck coefficient slightly fluctuates, varying from 27.7 to 22.7 μV/K, and the thermal conductivity slightly increases, but the electrical conductivity increases remarkably, and thus leads to enhance the figure of merit (ZT) obviously. The highest ZT of 8.71 × 10−4 at 120 °C was found in the composite with 80 wt.% MWNT.Figure optionsDownload full-size imageDownload as PowerPoint slide

•Decahedral platinum crystals were synthesized in the presence of graphite nanosheets.•Pt decahedra decorated graphene nanosheets show outstanding performance for FAO.•The superior activity is well correlated with the unique structures of Pt decahedra.Synthesis of five-twined platinum decahedra is currently a great challenge. Reported herein is a solution synthesis of ultrafine decahedral platinum crystals (average size 5.9 nm) mediated by graphite nanosheets together with poly (dimethyl diallyl ammonium chloride). The graphite nanosheets play a critical role in the formation of Pt decahedra. The obtained Pt decahedral crystals provide a valuable platform for the fundamental study of facet-dependent activity of platinum. The hybrid of Pt decahedral crystal decorated graphite nanosheets shows outstanding activity and durability for the oxidation of formic acid. The hybrid possesses a remarkable current density of 4.3 mA cm−2, which is 2 times that of state-of-the-art Pt/C catalyst. The superior catalytic performance is well correlated with the unique structures of decahedral Pt crystals. The synthesis protocol disclosed in this study would pave a new route to fabricate high-performance electrocatalysts for fuel cells.Download high-res image (132KB)Download full-size image

Comb-shaped sulfonated poly(arylene ether)s exhibit excellent properties when applied in proton exchange membranes (PEMs). However, few investigations have reported the use of comb-shaped sulfonated polymers with highly branched backbones as PEMs. In this work, a series of highly branched sulfonated poly(arylene ether)s with flexible alkylsulfonated side chains were successfully synthesized for the first time. The branched polymers were soluble in polar organic solvents and could be cast to form tough and smooth films. The membranes exhibited good overall properties as PEMs. With an increasing degree of branching (DB) value, properties such as oxidative stability, proton conductivity and swelling ratio of the membranes were significantly improved. The membrane with the highest DB value (8%) exhibits high proton conductivity (0.33 S cm−1 at 80 °C) and excellent oxidative stability (445 min) as well as acceptable mechanical properties (20.51 MPa), which indicate that this material is a good candidate PEM for evaluation in fuel cell applications.

As representative conjugated polymers, the physical properties, such as electric conductivity and electro-optic properties, of poly-Schiff bases (PSBs) have been widely investigated. However, to date, the thermoelectric (TE) properties of PSB or related polymers remain unreported. In this study, PSB with a donor–acceptor structure (PSB(A)) was synthesized and was blended with different fillers to prepare polymer–inorganic TE composites. For comparison, PSB with the common structure (PSB(B)) was also synthesized, and PSB(B)–graphite composites were fabricated. The PSB(A)/graphite composites exhibited a higher power factor of 10.2 μW m−1 K−2 compared with 4.5 μW m−1 K−2 of the PSB(B)/graphite composites at the same doping level. The effects of different fillers on the TE properties of the PSB(A)-based composites were investigated in detail, and the highest TE figure of merit, ZT = 2.53 × 10−3, was obtained. The results show that excellent TE materials could be produced by preparing polymer–inorganic TE composites using novel conducting polymers with a special structure (e.g., donor–acceptor structure) and conducting fillers.

Highly branched polymers applied as low-temperature proton exchange membranes (LTPEMs) have attracted attention from researchers because of their outstanding properties. However, there are few reports on the use of branched polymers as high-temperature proton exchange membranes (HTPEMs). In this work, a series of highly branched polybenzimidazoles (PBIs) with 1,3,5-tri(4-carboxyphenoxy)benzene (B3) as a branching agent were designed and successfully synthesized for the first time. The highly branched PBIs were soluble in polar organic solvents and could be cast to form tough and smooth films. Compared with linear PBI membranes, the branched PBI membranes with a 9% degree of branching exhibited a high phosphoric acid (PA) doping level of 10.5 (PA molecules per repeat unit), high proton conductivity (0.043 S cm−1) at 180 °C under anhydrous conditions, high resistance to oxidation and good PA retention ability. All these properties indicate that branched PBI membranes are promising for HTPEMs and can be potentially used in HTPEM fuel cells.