Kyungmun Kang

Evaluation and Fabrication of Composite Bipolar Plate to Develop a Light Weight Direct Methanol Fuel Cell Stack for Small-scale UAV Application (I)

Abstract >> A bipolar plate is a major component of a fuel cell stack, which occupies 50～60% of the totalweight and over 50% of the total cost of a typical fuel cell stack. In this study, a composite bipolar plate isdesigned and fabricated to develop a compact and light-weight direct methanol fuel cell (DMFC) stack for a small-scale Unmanned Aerial Vehicle (UAV) application. The composite bipolar plates for DMFCs are preparedby a compression molding method using resole type phenol resin as a binder and natural graphite and carbonblack as a conductor filler and tested in terms of electrical conductivity, mechanical strength and hydrogen permeability. The flexural strength of 63 MPa and the in-plane electrical conductivities of 191 S cm -1 are achieved under the optimum bipolar plate composition of phenol : 18%; natural graphite : 82%; carbon black : 3%, indicating that the composite bipolar plates exhibit sufficient mechanical strength, electrical conductivity and hydrogen permeability to be applied in a DMFC stack. A DMFC with the composite bipolar plate is tested and shows a similar cell performance with a conventional DMFC with graphite-based bipolar plate.

Graphene structured sulfonated poly(ether sulfone)s containing hexabenzocoronene for PEMFC

The novel sulfonated poly(ether sulfone)s containing hexabenzocoronene moiety that is partial graphene structure were synthesized and characterized their properties. Graphene is an allotrope of carbon and one-atom-thick planar sheets of sp2-bonded carbon atoms that are densely packed in a honeycomb crystal lattice. Poly(arylene ether sulfone)s containing hexaphenyls on polymer backbone were synthesized by polycondensation and followed intra-cyclization by Friedel-Craft reaction with Lewis acid (FeCl3) to form partial graphene structure. The sulfonation was taken selectively on hexabenzocoronen units with concentrated sulfuric acid. The structure properties of the sulfonated polymers were investigated by 1H-NMR spectroscopy. The resulted ion exchange capacities (IEC) were 1.09~1.61 meq./g. The water uptakes were 8.84~15.27% at 30°C and 18.27%~42.38% at 80°C with changing the ion exchange capacities. The S-PDHTPE membranes exhibit proton conductivities (80 °C, RH 90) of 78.3~ 105.7 mS/cm compared with 106.2 mS/cm of Nafion 211®.

Preparation and properties of hydroxide conducting membrane of poly(tetra phenyl ether sulfone) containing pendant quaternary ammonium hydroxide group for alkaline fuel cell application

Poly(tetra phenyl ether sulfone)s (PTPES) were functionalized with quaternary ammonium salt groups in order to investigate their properties as novel polymeric hydroxide exchange membrane materials. The PTPES-QAH (quaternary ammonium hydroxide)s were synthesized via chloromethylation of PTPESs, followed by reactions with chloromethylmethylether and ZnCl2, SOCl2 as Lewis acid catalyst, and then quaternized ammonium hydroxide with immersion of trimethylamine solution. The presence of CH2Cl groups in chloromethylated PTPES and PTPES-QAH were confirmed by 1H-NMR. Different contents of ammonium unit of PTPES-QAH (15, 20, 25 mol% of BHPTPB) were studied by FT-IR, 1H NMR spectroscopy, and thermo gravimetric analysis (TGA). Sorption experiments were conducted to observe the interaction of PTPES-QAH with water. The ion exchange capacity (IEC) and proton conductivity of PTPES-QAH were evaluated with different degree of quaternization.

Develop of advanced bipolar plate using carbon fiber prepreg and graphite/polymer composite materials

In this study, we introduce an advanced composite bipolar plate (BP) to improve mechanical behaviors of BPs as compared to conventional composite BPs. The new BPs are fabricated by compression molding process in which the mixture of natural graphite particles as a major filler, synthetic graphite and carbon blacks (CBs) as the additive are compacted and integrated with epoxy-carbon fiber prepreg. The new BPs are evaluated and the test results clearly demonstrate that the proposed BP is superior to typical carbon composite BPs in terms of key BP properties including electrical conductivity with emphasis on its outstanding flexural strength. The unique feature of this new BP enables to further reduce the thickness of BPs, which directly contributes the reduction in fuel cell stack weight and volume.

Fabrication and evaluation of composite bipolar plate to develop a compact and lightweight direct methanol fuel cell stack

A bipolar plate is a major component of a fuel cell stack, occupying a considerable portion of the overall stack cost and weight. In this study, a composite bipolar plate is designed and fabricated to develop a compact and lightweight direct methanol fuel cell (DMFC) stack for small-scale Unmanned Aerial Vehicle (UAV) applications. The composite bipolar plates for DMFCs are prepared with two different natural graphite particles, phenol resin and carbon black (CB) and fabricated by compression molding method. Then, the bipolar plates are tested in terms of electrical conductivity, mechanical strength and hydrogen permeability. The flexural strength of 63 MPa and the in-plane electrical conductivities of 191 S/cm are achieved under the optimum composition of bipolar plate materials with 18 wt.% phenol resin, 82 wt.% natural graphite, and 3 wt.% CB, which demonstrates that the composite bipolar plates exhibit sufficient mechanical strength, electrical conductivity and gas impermeability to be applied in a DMFC stack. A DMFC with the composite bipolar plate is tested and shows a superior cell performance as compared with a DMFC with a typical pure graphite-based bipolar plate.

Development of a Lightweight 200W Direct Methanol Fuel Cell Stack for UAV Applications and Study of its Operating Characteristics (II)

Abstract >> A lightweight 200W direct methanol fuel cell (DMFC) stack is designed and fabricated to powera small scale Unmanned Aerial Vehicle (UAV). The DMFC stack consists of 33-cells in which membrane-electrodeassemblies (MEAs) having an active area of 88 cm 2 are sandwiched with lightweight composite bipolar plates.The total stack weight is around 3.485 kg and stack performance is tested under various methanol feed concentrations. The DMFC stack delivers a maximum power of 248 W at 13.2 V and 71.3℃ under methanol feed concentrationof 1.2 M. In addition, the voltage of individual cell in the 33-cell stack is measured at various current levelsto ensure the stability of DMFC stack operations. The cell voltage distribution data exhibit the maximum cell voltage deviation of 28 mV at 15 A and hence the uniformity of cell voltages is acceptable. These results clearlydemonstrate that DMFC technology becomes a potential candidate for small-scale UAV applications. Key words : Direct methanol fuel cell, DMFC(직접메탄올연료전지), Unmanned aerial vehicle, UAV(무인비행기),Fuel cell stack(연료전지 스택), Methanol crossover(메탄올 크로스오버)