Investigation of a copper etching technique to fabricate metallic gas diffusion media

A new fabrication technique based on etching is employed to convert a copper foil into a porous structure with an array of micron size pores. The motivation stems from the need to develop a more efficient and controllable gas diffusion medium for fuel cell applications. The influence of mask shape, mask width and etching time was investigated experimentally. A correlation to predict trench width with etching time was derived; normalizing by mask width allows one to collapse the data. The etching rates to obtain micro-scale features, which are of the order of 1-2 mu m min(-1), are mainly dominated by the mask width due to mass-transport resistance. It is possible to control the pore dimensions, porosity and pore size distributions with this technique.