Surface modification of multiwall carbon nanotubes and its effect on mechanical and through‐plane electrical resistivity of PEMFC bipolar plate nanocomposites

Abstract

In this work, we showed how the functionalization of multiwall carbon nanotubes (MWCNT) by nitric acid (HNO 3 ) and their predispersion into poly (butylene terephthalate) (PBT) improved the through-plane electrical conductivity and mechanical properties of co-continuous morphology polyvinylidene fluoride (PVDF)/poly (ethylene terephthalate) (PET)/carbon black (CB)/graphite (GR)/MWCNT nanocomposites. First, when MWCNT were functionalized with HNO 3 then premixed with PBT, they showed no aggregations inside the PBT matrix due to their improved interfacial interactions and chemical compatibility with the PBT matrix. Then, when PBT/ (HNO 3 -functionalized MWCNT) mixture was added in small quantities to (PET/PVDF)/(CB/GR) composites, it decreased significantly their through-plane resistivity and enhanced their impact and flexural properties. Its synergistic effect also led to the best proton exchange membrane fuel cell bipolar plate prototypes (smoother surface, without any cracks). | INTRODUCTIONProton exchange membrane fuel cell (PEMFC) technology is considered as one of the most promising future technologies for industrial and transportation applications. A lot of work has been done to develop lightweight and good performance PEMFC components.Bipolar plates (BPPs) are ones of the main components that got more research focus. Bipolar plates comprise the major part, by weigh and volume, of PEMFC stack. They also represent 40% to 50% of its cost. 1 Thus, the development of appropriate and low cost materials for BPPs becomes a key factor for PEMFCs commercialization.To date, metals, graphite (GR), and polymer composites are the 3 types of materials that are mainly used for the fabrication of BPPs.Metallic BPPs could offer a good electrical conductivity, excellent mechanical properties, and ease of fabrication. However, their operating environment exposes them to a pH of 2 to 3 for temperatures around 80°C, leading to their corrosion or even their dissolution. This could poison the membrane and considerably affect its ionic conductivity if the BPPs are not protected with expensive corrosion-resistant metallic coatings.1-3 Although they have excellent corrosion resistance and high electrical conductivity, BPPs made from GR are heavy, brittle, and require precise machining of flow channels, leading to higher costs. Mighri et al 4 tested different conductive additives with thermoplasticcomposites based on polypropylene and polyphenylene sulfide. The lowest through-plane resistivity was obtained by using a combination of high surface area carbon black (CB) and synthetic GR. However, due to the high CB/GR concentration needed, the blends viscosity largely increased so that BPP manufacturing became more difficult.To find a compromise between blends processability and their corresponding BPP properties, Bouatia et al 5 developed poly (ethylene terephthalate) (PET)-based blends by twin-screw extrusion process. In addition to CB/GR combination, silver-coated glass particles were also added to decrease BPP through-plane resistiv...

Effect of carbon nanotubes modified with different concentrations of rare earth lanthanum on the mechanical and tribological properties of epoxy composites

“…First, the CNTs were acidified to acquire acidified ACNTs and the specific process of acidification is given in. 27 , 29 , 30 The intention of acidification treat is to generate oxygen-containing functional groups (e.g. -OHs and -COOHs) on the exterior of the CNTs.…”

A review on key factors influencing the electrical conductivity of proton exchange membrane fuel cell composite bipolar plates

“…This notable reduction was not achievable with CB alone. In a subsequent study by Athmouni et al, 111 MWCNT‐modified with HNO 3 were dispersed in poly(butylene terephthalate) (PBT). They added this nanocomposite to a mixture comprising 55 wt.% of (PET/PVDF 50:50) and 45% of (CB/G 50:50).…”

Current status of research on composite bipolar plates for proton exchange membrane fuel cells (PEMFCs): nanofillers and structure optimization

“…Similarly, Athmouni N. et al 119 studied the effect of functional group-functionalized MWCNT on the performance of composite bipolar plates, and they prepared MWCNT-COOH/PBT composite bipolar plates through nitric acid oxidation with MWCNTs and pre-blending MWCNT-COOH with polybutylene terephthalate (PBT). Due to the enhanced van der Waals force, the interface bonding between MWCNTs and PBT resin is greatly enhanced, resulting in a tighter interface bonding between resin and MWCNTs, effectively improving the mechanical properties.…”