Shu-Hang Liao

Preparation and properties of a graphene reinforced nanocomposite conducting plate

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.

One-step functionalization of carbon nanotubes by free-radical modification for the preparation of nanocomposite bipolar plates in polymer electrolyte membrane fuel cells

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.

Electrical, mechanical and thermal properties of high performance polymer nanocomposite bipolar plates for fuel cells

Abstract: Proton exchange membrane fuel cells (PEMFC) have received attention owing to their low operating temperature and quick start-up. Fuel cells have high material costs, low power density and short lifetime, which are major barriers to their use. In order to become commercially viable, PEMFC bipolar plates must be cheaper, lighter, and more compact. Here, carbon nanotubes (CNTs) are assessed as a reinforcement for either thermoplastic or thermoset-based nanocomposite bipolar plates, because of such properties as superior mechanical strength, high electrical and thermal properties, and light weight. CNTs have strong intrinsic van der Waals forces with each other, which hold together in ropes and bundles, resulting in very low solubility in most solvents. Therefore, homogeneous dispersion of CNTs in the matrix is key. How to achieve homogeneous dispersion of CNTs by chemical modification is discussed. Owing to the formation of effective 3D electrical conducting networks better properties are obtained such as high mechanical strength, improved electrical conductivity and cell performance when the functionalized CNT is incorporated in a bipolar plate. Functionalized CNT reinforcement is a promising method to manufacture alternative high performance bipolar plates for PEM fuel cell applications.