(259a) Nano Composite Material Based Gas Diffusion Layer for Proton Exchange Membrane Fuel Cell

Gas diffusion layers (GDLs) were fabricated using commercially available carbon paper as macro-porous layer substrate. Functionally graded nano-porous layers were designed by combining carbon nano-fibers with nano-chain type Pureblack carbon (75:25–0:100 wt.%) in the z-direction towards the catalyst layer and Teflon content (say 15–30 wt.%) to obtain variation in pore diameter and also hydrohobicity. On the top of the nanoporous layer, a thin layer of hydrophilic inorganic oxide (fumed silica) was also deposited to retain moisture content to maintain the electrolyte wet, especially when the fuel cell is working at lower relative humidity (RH) conditions, which is typical for automotive applications. The surface morphology, contact angle, bulk characteristics and pore size distribution of the layered GDLs were examined using FESEM, Goniometer, Interferometer and Hg Porosimeter, respectively. The GDLs assembled into MEAs were evaluated in single cell PEMFC under various operating conditions (temperature and RH) using H2/O2 and H2/air as reactants. It was observed that the functionally graded nano-porous GDLs with hydrophilic layer showed an excellent fuel cell performance with a peak power density of about 0.46 W/cm2 at 85 ◦C using H2 and air at 50% RH.

Prompted by our earlier study that fumed silica on gas diffusion layer favored a performance improvement of the single fuel cell at lower RH conditions, the present study has been carried out with inorganic oxides in the nanoscale such as TiO2, Al2O3, commercially available mixed oxides, hydrophilic silica and aerosil silica. The structure of each of the oxide coating on the GDL surface has resulted in refinement with graded pore dimension as seen from the Hg porosimetry data. The fuel cell evaluation at various RH conditions (50–100%) revealed that the performance of all the inorganic oxides loaded GDL is very high compared to that of pristine GDL. The results confirm our earlier observation that inorganic oxides on GDL bring about structural refinement favorable for the transport of gases, and their water retaining capacity enable a high performance of the fuel cell even at low RH conditions.