Titanium Nitride - Polytetrafluoroethylene Composite Coating on Carbon Paper as Gas Diffusion Layer of Proton Exchange Membrane Fuel Cells

Titanium nitride (TiN)-modified hydrophobic-treated carbon paper (CP) was prepared by impregnating CP with polytetrafluoroethylene (PTFE) emulsion containing TiN nanoparticles (NPs). Electrochemical measurements showed that CP witnessed an increase in corrosion resistance and electrical resistivity after treated with 5 wt% PTFE emulsion. Since the sacrifice in electrical conductivity is not beneficial to the application in proton exchange membrane fuel cells (PEMFCs), conductive ceramic NPs – TiN NPs were introduced into the CP to further improve its electrical conductivity. It was found that after adding TiN NPs, the electrical resistivity of CP (immersed in 5 wt% PTFE emulsion containing 8 wt% TiN NPs) decreased to a level (3.8 mΩ cm) similar to that of untreated CP (3.5 mΩ cm), and meanwhile there is a further improvement in corrosion resistance, where the corrosion current density (at 1.4 V) of TiN-modified CP stabilises at the lowest value of 5.50 μA/cm2, as compared with 32.8 and 12.7 μA/cm2 for raw CP and PTFE-treated CP. According to microstructure characterisation, these improvements could be attributable to the formation of conductive networks and improved PTFE distribution due to the addition of TiN NPs.