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9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) has been grafted onto the surface of graphene oxide (GO) by reacting epoxy ring groups together with the reduced graphene structure (DOPO-rGO). X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and UV–vis spectroscopy confirm that DOPO not only covalently bonded to the GO, as a functionalization moiety, but also partly restored the conjugate structure of GO, as a reducing agent. A pelletlike structure of DOPO on rGO sheets was observed by means of transmission electron microscopy (TEM), contributing to good dispersion of rGO in nonpolar toluene. Furthermore, the flame retardancy and thermal stability of DOPO-rGO/epoxy nanocomposites containing various weight fractions of DOPO-rGO were investigated by the limiting oxygen index (LOI) test and thermogravimetric analysis (TGA) in nitrogen. Significant increases in the char yield and LOI were achieved with the addition of...

This study employed a solution-based method to prepare a 3-D hybrid material comprising graphene and acid-treated multi-walled carbon nanotubes (MWCNTs). The adsorption of MWCNTs on graphene reduces the π – π interaction between graphene sheets resulting from steric hindrance, providing a subsequent reduction in aggregation. Optimal proportions of MWCNTs to graphene (2:1) enabled the even distribution of individual MWCNTs deposited on the surface of the graphene. The hybrid 3-D material was incorporated within a TiO 2 matrix and used as a working electrode in dye-sensitized solar cells (DSSCs). The hybrid material provides a number of advantages over electrodes formed of either MWCNTs or graphene alone, including a greater degree of dye adsorption and lower levels of charge recombination. In this study, DSSCs incorporating 3-D structured hybrid materials demonstrated a conversion efficiency of 6.11%, which is 31% higher than that of conventional TiO 2 -based devices.

The focus of this study was placed on the lightness of microwave absorbing effective metal/epoxy composites. For such a focus, high aspect ratio of flake iron powder and high absorbing FeNi 3 were prepared. The iron powder particle size was reduced significantly through wet milling, comparing to dry milling. The FeNi 3 alloy powders were synthesized by mechanical alloying (MA); then, the particle size was reduced through wet milling. The iron powder and FeNi 3 alloy were characterized by scanning electron microscopy (SEM) and X-ray diffraction. SEM of the metal particles showed the flake and small structure by wet milling. The microwave absorbing effectiveness of metal/epoxy composite was affected by the structure, loading and dispersion of metal materials. The polyvinylpyrrolidone (PVP) plays an important role in suspending metal powders in wet milling to reduce powder size. Besides, the PVP will be a coupling agent in inhibiting the aggregation and enhancing the interfacial interaction between metal and epoxy. Results suggested that after the above manufacturing process, the microwave absorbency was enhanced substantially. Composite films of Fe/epoxy and FeNi 3 /epoxy 1.6 mm in thickness possessed a microwave absorbency above 10 dB at 9.2–15.2 GHz and 13.1–16.2 GHz, respectively.

This study uses a low temperature thermal chemical vapor deposition with an applied external magnetic field to grow carbon nanotubes (CNTs) on Ni/Ag-printed glass substrates. A mixture of C 2 H 2 and H 2 gas was used for the growth of the CNTs. A Ni catalyst layer was deposited on the Ag-printed glass substrate by pulse electroplating. Scanning electron micrographs as well as the presence of two sharp peaks at 1320 cm −1 (D band) and 1590 cm −1 (G band) in the Raman spectra indicate that the graphitized structure of CNTs synthesized under a magnetic field has higher quality (i.e., a D-band to G-band intensity ratio of 0.303) than CNTs synthesized without a magnetic field. Transmission electron micrographs show a fine Ni catalyst at the tip of the tube for CNTs synthesized under a magnetic field, exhibiting a CNT “tip-growth” model. The synthesis of CNTs in the presence of a magnetic field also generates better field emission properties and better lighting morphology than without a magnetic field.

Polypropylene-grafted multi-walled carbon nanotubes (MWCNTs/PP-g-MA) were prepared via a ring-opening reaction between polypropylene grafted maleic anhydride (PP-g-MA) and animated MWCNTs by a solution process. The prepared MWCNTs/PP-g-MA were introduced to the PP nanocomposite bipolar plates, to achieve a high compatibility and good adhesion between MWCNTs and the immiscible PP matrix through PP-g-MA chains. Replacement of amine-terminated groups by PP-g-MA on the MWCNTs leads to covalent grafting of longer copolymer chains to the MWCNTs, and to improve the dispersion of MWCNTs in the PP matrix. The resulting PP nanocomposite bipolar plates with 1, 2, and 4 wt% of MWCNTs/PP-g-MA demonstrates not only improved flexural strengths by 56.3, 68.5, and 70.9%, but also enhanced bulk electrical conductivities by 282, 425, and 473%, respectively, over those of the neat composite bipolar plates. The contact resistance of the MWCNTs/PP-g-MA/PP nanocomposite bipolar plate is 9.1 mOhm cm2, which is lower than the D.O.E. target ∼10 mOhm cm2 in the year 2010. The maximum current density and power density of the single cell test for the nanocomposite bipolar plate with 4 wt% MWCNTs/PP-g-MA are 1.41 A cm−2 and 0.586 W cm−2, respectively, which are 12.4 and 4.56% slightly lower than those of graphite plates. Comparing with pristine MWCNTs/PP nanocomposite bipolar plates, MWCNTs/PP-g-MA/PP nanocomposite bipolar plates are suitable for bipolar plates of polymer electrolyte membrane fuel cells.

In this study, the novel functionalized multi-walled carbon nanotubes (MWCNTs) are used as cross-links between MWCNTs–vinyl ester interfaces to achieve homogeneous dispersion and strong interfacial bonding for developing fully integrated MWCNTs–vinyl ester nanocomposite bipolar plates. POAMA (i.e. poly(oxyalkylene)-amines (POA) bearing maleic anhydride (MA)) are grafted onto the MWCNTs by amidization reaction, forming MWCNTs-POAMA. In the MWCNTs-POAMA/vinyl ester nanocomposites, MWCNT-POAMAs react with vinyl ester and become part of the cross-linked structure, rather than just a separate component. It is found that the MWCNTs-POAMA exhibited better dispersion in the vinyl ester matrix than those of pristine MWCNTs. Moreover, the results demonstrate that the mechanical and electrical properties of the vinyl ester nanocomposite bipolar plate are improved dramatically. The ultimate flexural strength, unnotched impact strength, in-plane electrical conductivity and contact resistance of the MWCNTs-POAMA/vinyl ester nanocomposite bipolar plate are increased by 45%, 90%, 315% and 28%, respectively. In addition, the maximum current and power densities of the single fuel cell test using the MWCNTs-POAMA/vinyl ester nanocomposite bipolar plates is enhanced from 1.03 to 1.23 A cm −2 and from 0.366 to 0.518 W cm −2 , respectively, which suggested that a higher electron transfer ability for polymer electrolyte membrane fuel cell applications can be achieved.

This study investigates the flowability of the bulk-molding compound (BMC) on composite bipolar plates containing graphite content from 70 to 80 wt% with different graphite sizes. A small quantity (from 0.25 to 2 wt%) of multi-walled carbon nanotubes (MWCNT) is also added. Findings show that the flowability of BMC material decreases with decreasing graphite size and with increasing graphite content. The BMC material containing large size graphite (177–125 μm) entirely exhibits a relatively higher flowability within the analysis graphite contents, in the range of 73.3–11.3 cm, compared to the small size (74–45 μm), in which flowability is in the range of 40.3–6.67 cm. Further adding MWCNT causes decreased flowability of the BMC material especially when the percolated networking structure is formed through the resin. Therefore, with flowability below 10 cm, the formability of a large area (300 mm × 300 mm × 3 mm) or thin (100 mm × 100 mm × 0.5 mm) composite bipolar plate shows a large area of surface porosity or visible defects. Results indicate that the flowability of the thermoset-based BMC material is an important design parameter to fabricate cost-effective, large, or thin composite bipolar plates.

Direct functionalized carbon nanotubes (CNTs) were utilized to form the heat flow network for epoxy composites through covalent integration. A method of preparing a fully heat flow network between benzenetricarboxylic acid grafted multi-walled carbon nanotubes (BTC-MWCNTs) and epoxy matrix is described. A Friedel–Crafts modification was used to functionalize MWCNTs effectively and without damaging the MWCNT surface. Raman spectra, X-ray photoelectron spectra and thermogravimetric analysis reveal the characteristics of functionalized MWCNTs. The scanning electron microscope images of the fracture surfaces of the epoxy matrix showed BTC-MWCNTs exhibited higher solubility and compatibility than pristine-MWCNTs. The MWCNTs/epoxy composites were prepared by mixing BTC-MWCNTs and epoxy resin in tetrahydrofuran, followed by a cross-linking reaction with a curing agent. The BTC was grafted onto the MWCNTs, creating a rigid covalent bond between MWCNTs and epoxy resin and forming an effective network for heat flow. The effect of functionalized MWCNTs on the formation of the heat flow network and thermal conductivity was also investigated. The thermal conductivity of composites exhibits a significant improvement from 0.13 to 0.96 W/m K (an increase of 684%) with the addition of a small quantity (1–5 vol%) of BTC-MWCNTs.

Multiwalled carbon nanotubes (MWCNTs) are covalently modified with different molecular weights 400 and 2000 poly(oxyalkylene)-amine bearing the diglycidyl ether of bisphenol A (DGEBA) epoxy (POA400-DGEBA and POA2000-DGEBA) oligomers. The oxidized MWCNTs (MWCNTs-COOH) are converted to the acid chloride-functionalized MWCNTs, followed by the reaction with POA-DGEBAs to prepare the MWCNTs/POA400-DGEBA and MWCNTs/POA2000-DGEBA. FTIR, thermogravimetric analysis (TGA) and high resolution X-ray photoelectron spectra (XPS) reveal that the POA-DGEBAs are covalently attached to the surface of MWCNTs. The morphology of MWCNTs/POA-DGEBA is observed by TEM. The POA400-DGEBA coated on the MWCNTs is thicker and more uniform. However, the coating of POA2000-DGEBA on the MWCNTs shows a worm-like bulk substance and the MWCNT surface is bare. In addition, the flexural strength and the bulk electrical conductivity of the MWCNTs/polypropylene nanocomposite bipolar plates are measured 59% and 505% higher than those of the original composite bipolar plates by adding 8 phr of MWCNTs/POA400-DGEBA. The maximum current density and power density of the single cell test for the nanocomposite bipolar plate with 4 phr MWCNTs/POA400-DGEBA are 1.32 A cm −2 and 0.533 W cm −2 , respectively. The overall performance confirms the functionalized MWCNTs/polypropylene nanocomposite bipolar plates prepared in this study are suitable for PEMFC application.

This study prepares novel metal mesh hybrid polymer composite bipolar plates for proton exchange membrane fuel cells (PEMFCs) via inserting a copper or aluminum mesh in polymer composites. The composition of polymer composites consists of 70 wt% graphite powder and 0–2 wt% modified multi-walled carbon nanotubes (m-MWCNTs). Results indicate that the in-plane electrical conductivity of m-MWCNTs/polymer composite bipolar plates increased from 156 S cm −1 (0 wt% MWCNT) to 643 S cm −1 (with 1 wt% MWCNT) (D.O.E. target >100 S cm −1 ). The bulk thermal conductivities of the copper and aluminum mesh hybrid polymer composite bipolar plates (abbreviated to Cu-HPBP and Al-HPBP) increase from 27.2 W m −1 K −1 to 30.0 W m −1 K −1 and 30.4 W m −1 K −1 , respectively. The through-plane conductivities decrease from 37.8 S cm −1 to 36.7 S cm −1 for Cu-HPBP and 22.9 S cm −1 for Al-HPBP. Furthermore, the current and power densities of a single fuel cell using copper or aluminum mesh hybrid polymer composite bipolar plates are more stable than that of using neat polymer composite bipolar plates, especially in the ohmic overpotential region of the polarization curves of single fuel cell tests. The overall performance confirms that the metal mesh hybrid polymer composite bipolar plates prepared in this study are promising for PEMFC application.

This study develops cost effective and high performance composite conductive plates for use in dye-sensitized solar cells (DSSCs). Composite plates with various graphite contents at a constant carbon nanotube (CNT) loading were prepared by bulk molding compound (BMC) process. Results show that the bulk electrical resistance of the composite plate gradually decreases from 6.7 mΩ cm to 1.7 mΩ cm as the graphite content increases, which is due to the formation of efficient electronic conducting networks. For DSSCs, the composite plates may be suitable substitutes for the conductive glass plates in the counter electrodes substrates of DSSCs. Results reveal that composite plates at the optimum level (80 wt.% graphite loading) provide lower cell resistance, lower preparation cost and higher cell performance than common conductive glass plates. Therefore, in order to decrease the cost of the cells and to maintain good cell performance, this graphite-like composite plate prepared by the BMC process is a promising substitute component for DSSCs.

The functionalized multi-walled carbon nanotubes (MWCNTs) had been prepared via Friedel–Crafts acylation with maleic anhydride. X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA) confirmed the functionalization of MWCNTs. The composites with maleic anhydride modified MWCNTs (Mah-g-MWCNTs) and poly (methyl methacrylate) were then prepared by the in situ and ex situ solution polymerization system. The Electromagnetic Interference (EMI) shielding effectiveness (SE) of Mah-g-MWCNTs/PMMA composites increased with the increasing of the Mah-g-MWCNTs content, and the in situ system shows higher EMI SE value. The wear resistance was enhanced while the loading of the Mah-g-MWCNTs was above the percolation threshold, and the in situ system provides higher efficiency than that of ex situ system.

Various molecular weights of poly(propylene oxide) diamines oligomers/Nafion® acid–base blend membranes were prepared to improve the performance of Nafion® membranes in direct methanol fuel cells (DMFCs). The acid–base interactions were studied by Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC). The performance of the blend membranes was evaluated in terms of methanol permeability, proton conductivity and cell performance. The proton conductivity was slightly reduced by acid–base interaction. The methanol permeability of the blend D2000/Nafion® was 8.61 × 10−7 cm2 S−1, which was reduced 60% compared to that of pristine Nafion®. The cell performance of D2000/Nafion® blend membranes was enhanced significantly compared to pristine Nafion®. The current densities that were measured with Nafion® and 3.5 wt% D2000/Nafion® blend membranes were 62.5 and 103.5 mA cm−2, respectively, at a potential of 0.2 V. Consequently, the blend poly(propylene oxide) diamines oligomers/Nafion® membranes critically improved the single-cell performance of DMFC.

This study aims at the fabrication of lightweight and high performance nanocomposite bipolar plates for the application in polymer electrode membrane fuel cells (PEMFCs). The thin nanocomposite bipolar plates (the thickness

Novel multiwalled carbon nanotubes (MWNTs) were prepared using poly(oxypropylene)-backboned diamines of molecular weights M w 400 and 2000 to disperse acid-treated MWNTs, improving the performance of composite bipolar plates in polymer electrolyte membrane fuel cells. A lightweight polymer composite bipolar plate that contained vinyl ester resin, graphite powder and MWNTs was fabricated using a bulk molding compound (BMC) process. Results demonstrate that the qualitative dispersion of MWNTs crucially determined the resultant bulk electrical conductivity, the mechanical properties and the physical properties of bipolar plates. The flexural strength of the composite bipolar plate with 1 phr of MWNTs was approximately 48% higher than that of the original composite bipolar plate. The coefficient of thermal expansion of the composite bipolar plate was reduced from 37.00 to 20.40 μm m −1 °C −1 by adding 1 phr of MWNTs, suggesting that the composite bipolar plate has excellent thermal stability. The porosity of the composite bipolar plate was also evaluated. Additionally, the bulk electrical conductivity of the composite bipolar plate with different MWNTs types and contents exceeds 100 S cm −1 . The results of the polarization curves confirm that the addition of MWNTs leads to a significant improvement on the single cell performance.

A novel organic–inorganic mesoporous silica (L64 copolymer-templated mesoporous SiO 2 ), functionalized with perfluoroalkylsulfonic acid groups analogous to that of Nafion ® , was prepared. A condensation reaction between the surface silanol groups of the mesoporous silicas and 1,2,2-trifluoro-2-hydroxy-1-trifluoromethylethane sulfonic acid Beta-sultone was conducted. High proton-conducting Nafion ® /functionalized mesoporous silica composite membranes were prepared via homogeneous dispersive mixing and the solvent casting method. In this investigation, the proton conductivity ( σ ) of the composite membrane is increased from 0.10 to 0.12 (S cm −1 ) as the modified mesoporous silica content is increased from 0 to 3 wt%. The methanol permeability of the composite membrane declined as the sulfonic mesoporous silica content increased. The methanol permeability of the composite membrane that contained 3 wt% M–SiO 2 –SO 3 H was 4.5 × 10 −6 cm 2 S −1 —30% lower than that of pristine Nafion ® . Results of this study demonstrate a significant improvement in the performance of DMFCs.

Various spatially enlarged organoclays were prepared by using poly(oxyproplene)-backboned quaternary ammonium salts of various molecular weights M w 230, 400 and 2000 as the intercalating agents for Na + -montmorillonite. The modified MMT was utilized to improve the compatibility with Nafion ® . Sufficient interaction of the modified MMT with Nafion ® was studied by using X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS). The performance of the Nafion ® / m -MMT composite membranes for direct methanol fuel cell (DMFCs) was evaluated in terms of water uptake, ion exchange capacity (IEC), methanol permeability, proton conductivity, and cell performance. The methanol permeability of the composite membrane decreased with the increasing of m -MMT content. The proton conductivity of the membrane was lowered slightly from that of pristine Nafion ® membrane. These results led to an essential improvement in the single-cell performance of DMFCs.

This study aims at developing lightweight and high performance composite bipolar plates for use in polymer electrolyte membrane fuel cells (PEMFCs). The thin polymer composite bipolar plates (the thickness M w ) of poly(oxypropylene)-backboned diamine intercalating agents. Results indicate that the basal spacing and content of MMT varied with M w of POP-diamines are critical in determining the resultant mechanical properties for bipolar plates. Flexural strength of MMT composite plates was increased from 30.21 to 45.66 MPa by adding 2 phr of MMT. The flexural strength of the plate was also ca. 38% higher than the pristine graphite plate as the basal spacing of MMT was increased from 1.71 to 5.43 nm. Meanwhile, the unnotched impact strength of the composite plates was increased from 58.11 to 80.21 J m −1 . The unnotched impact strength of the plate was ca. 30% higher than that of the original graphite plates as the basal spacing of MMT was increased from 1.71 to 5.43 nm. The limiting oxygen index (LOI) and the UL-94 test revealed that the bipolar plate possesses excellent flame retardant with LOI >50 and UL-94-V0. The thermal decomposition temperature of each MMT composite plate is also higher than 250 °C. In addition, the bulk electrical conductivity of the bipolar plate with different MMT contents and basal spacing of MMT is higher than 100 S cm −1 . The corrosion current is less than 10 −7 A cm −2 . Results confirm that the addition of MMT leads to a significant improvement on the performance of the composite bipolar plate.

Multiwalled carbon nanotube (MWCNT)/epoxy composites are prepared, and the characteristics and morphological properties are studied. Scanning electron microscopy microphotographs show that MWCNTs are dispersed on the nanoscale in the epoxy resin. The glass-transition temperature (Tg) of MWCNT/epoxy composites is dramatically increased with the addition of 0.5 wt % MWCNT. The Tg increases from 167°C for neat epoxy to 189°C for 0.5 wt % CNT/epoxy. The surface resistivity and bulk resistivity are decreased when MWCNT is added to the epoxy resins. The surface resistivity of CNT/epoxy composites decreases from 4.92 × 1012 Ω for neat epoxy to 3.03 × 109 Ω for 1 wt % MWCNT/epoxy. The bulk resistivity decreases from 8.21 × 1016 Ω cm for neat epoxy to 6.72 × 108 Ω cm for 1 wt % MWCNT/epoxy. The dielectric constant increases from 3.5 for neat epoxy to 5.5 for 1 wt % MWCNT/epoxy. However, the coefficient of thermal expansion is not affected when the MWCNT content is less than 0.5 wt %. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1272–1278, 2007

Intriguing functionalities at nano-sized domain walls have recently spawned a new paradigm for developing novel nanoelectronics due to versatile characteristics. In this study, we explore a new scenario to modulate the local conduction of ferroic domain walls. Three controlling parameters, i.e., external electrical field, magnetic field and light, are introduced to the 90° domain walls (90° DWs) of BiFeO3. Electrical modulation is realized by electrical transport, where the mobility of 90° DWs can be altered by gating voltage. We further use the ferromagnetic/antiferromagnetic coupling to reveal the inherent magnetism at the DWs. With an established magnetic nature, magnetotransport has been conducted to introduce magnetic controlling parameter, where a giant positive magnetoresistance change can be observed up to 200%. In addition, light modulated conduction, a core factor for multifunctional applications, is successfully demonstrated (current enhancement by a factor of 2 with 11 W white lamp). These results offer new insights to discover the tunability of domain wall nanoelectronics.

When fabricated by thermal exfoliation, graphene can be covalently functionalized more easily by applying a direct ring-opening reaction between the residual epoxide functional groups on the graphene and the amine-bearing molecules. Investigation by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and transmission electron microscopy (TEM) all confirm that these molecules were covalently grafted to the surface of graphene. The resulting dispersion in an organic solvent demonstrated a long-term homogeneous stability of the products. Furthermore, comparison with traditional free radical functionalization shows the extent of the defects characterized by TEM and Raman spectroscopy and reveals that direct functionalization enables graphene to be covalently functionalized on the surface without causing any further damage to the surface structure. Thermogravmetric analysis (TGA) shows that the nondestroyed graphene structure provides greater thermal stability not only for the grafted molecules but also, more importantly, for the graphene itself, compared to the free-radical grafting method.

Novel metal mesh hybrid polymer composite bipolar plates for proton exchange membrane fuel cells (PEMFCs) have been prepared via inserting a copper or alumina mesh in polymer composites. The composition of polymer composites consisted of 70 wt% graphite powder and 0–2 wt% modified multi-walled carbon nanotubes (m-MWCNTs). Results indicated that the inplane electrical conductivity of m-MWCNTs/polymer composite bipolar plates increased from 156 S cm−1 (0 wt% MWCNT) to 643 Scm−1 (with 1 wt% MWCNT) (D.O.E target > 100 S cm−1 ). The bulk thermal conductivities of the copper and aluminum mesh hybrid polymer composite bipolar plates increased from 27.2 W m−1 K−1 to 30.0 W m−1 K−1 and 30.4 W m−1 K−1 , respectively. Furthermore, the current and power densities of a single fuel cell using copper or alumina mesh hybrid polymer composite bipolar plates are more stable than that of using neat polymer composite bipolar plates, especially in the ohmic overpotential region of the polarization curves of single fuel cell tests. The overall performance confirms that the metal mesh hybrid polymer composite bipolar plates prepared in this study are promising for PEMFC application.Copyright © 2009 by ASME

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Polypropylene was successfully covalently grafted onto the surface of thermally reduced graphite oxide (PP-g-TRGO) by taking advantage of the "residual oxygen-containing functional groups" and the "grafting to" method. The PP-g-TRGO obtained showed an improved compatibility, and interfacial interaction, with an isotactic PP (iPP) matrix. The iPP/PP-g-TRGO nanocomposite exhibited a dramatically improved thermal stability compared to that of neat iPP even at low loadings.

This study presents a novel nanocomposite conducting plate (CP) reinforced by graphene at a low weight fraction percentage, and compares the properties of this novel nanocomposite CP with those containing various weight fractions of multi-wall carbon nanotubes (MWCNT) (0.2, 0.5, and 1 phr). Adding only 0.2 phr of graphene as reinforcement remarkably enhanced the thermal, mechanical, and electrical properties of the nanocomposite CP. The coefficient of thermal expansion (CTE) of nanocomposite CP below the glass transition temperature (Tg) decreased from 49.7 μm−1 m °C−1 to 26.9 μm−1 m °C−1 and the CTE above Tg decreased from 119.2 μm−1 m°C−1 to 55.2 μm−1 m °C−1. Thermal conductivity increased from 18.4 W m−1 K−1 to 27.2 W m−1 K−1. The flexural strength increased from to 28.0 MPa to 49.2 MPa. The in-plane electrical conductivity increased from 155.7 S cm−1 to 286.4 S cm−1. The enhancement percentages of these properties are 47.8%, 75.7%, and 83.9%, respectively, which are much higher than that of the original composite CP. These results indicate that using graphene as reinforcement in the preparation of nanocomposite CP is effective in terms of cost and performance, because of the low cost the raw material, graphite, and the fact that a lower loading of graphene than of MWCNT can yield the same performance. Moreover, this novel multi-functional nanocomposite CP has wide potential for use in proton exchange membrane fuel cells (PEMFCs), direct methanol fuel cells (DMFCs), the dye-sensitized solar cells (DSSCs) counter electrode, and vanadium redox battery (VRB) applications.

This study fabricates dye-sensitized solar cells (DSSCs) based on TiO(2)/multi-walled carbon nanotube (MWCNT) nanocomposite photoanodes obtained by the modified acid-catalyzed sol-gel procedure. Results show that incorporating MWCNTs into a TiO(2)-based electrode efficiently improves the physicochemical properties of the solar cell. The results of dye adsorption and cell performance measurements indicate that introducing MWCNTs would improve the roughness factor (from 834 to 1267) of the electrode and the charge recombination of electron/hole (e(-)/h(+)) pairs. These significant changes could lead to higher adsorbed dye quantities, photocurrent and DSSC cell performance. Nevertheless, a higher loading of MWCNTs causes light-harvesting competition that affects the light adsorption of the dye-sensitizer, and consequently reduces the cell efficiency. This study suggests an optimum MWCNT loading in the electrode of 0.3 wt%, and proposes a sol-gel synthesis procedure as a promising method of preparing the TiO(2)-based nanocomposite.

This study presents a novel one-step preparation of functionalized multi-walled carbon nanotubes (MWCNTs) by free-radical modification. MA-POA, i.e.maleic anhydride (MA) grafted on molecular weight 400 and 2000 poly(oxyalkylene)amines (POA400 and POA2000), was attached onto the MWCNTs, forming MWCNTs/MA-POA400 and MWCNTs/MA-POA2000. The functionalized MWCNTs, especially MWCNTs/MA-POA2000, exhibited higher solubility than the pristine MWCNTs in organic solvents and were well dispersion in a vinyl ester matrix. Furthermore, this study also investigated mechanical, electrical and single fuel cell properties of functionalized MWCNT nanocomposite bipolar plates for use in polymer electrolyte membrane fuel cells (PEMFCs). The flexural strength of the nanocomposite bipolar plates containing 2 wt% MWCNTs/MA-POA2000 was increased from 28 MPa to 48.33MPa. In addition, the in-plane and through-plane electrical conductivities and half-cell resistance of the nanocomposite bipolar plates were 780%, 168% and 253%, respectivel,y higher than those of the original composite bipolar plates with the addition of only a small quantity (1 wt%) of MWCNTs/MA-POA2000. The maximum current density and power density of the single cell tests of the nanocomposite bipolar plate with 1 wt% MWCNTs/MA-POA2000 were enhanced from 1.03 to 1.32 A cm−2 and from 0.392 to 0.580 W cm−2, respectively. The overall performance confirms the MWCNTs/MA-POA2000 nanocomposite bipolar plates prepared in this study are suitable for PEMFC application.