Method of making fluid diffusion layers and electrodes having reduced surface roughness

The present invention relates to improved methods for making fluid diffusion layers and electrodes having reduced surface roughness and methods for making membrane electrode assemblies having better reliability and performance. The methods comprise adhering at least one loading material to a porous substrate in a manner such that the surface roughness of the resulting fluid diffusion layer is reduced. The reduced surface roughness may be assessed in terms of average surface roughness (R ) or by observation of infrared hot-spots detected. The present methods make fluid diffusion layers having reduced surface roughness. The methods used for adhering the loading material to the substrate surface can reduce the average surface roughness of the fluid diffusion layers, thereby reducing leaks in and damage to ion exchange membranes. When fluid diffusion layers and electrodes having reduced surface roughness are employed in membrane electrode assemblies, better reliability and performance are obtained. A method of calculating the surface roughness of a fluid diffusion layer may be used.