Femtosecond pulsed laser micromachining of titanium foils for producing hydrogen as an energy carrier

Proton exchange membrane electrolyzer cells are being developed as a cost-effective, sustainable route to generating hydrogen fuel for energy storage, advanced fuel production, metal refining, fertilizer, and many other applications. Designs using custom-made thin, metallic foil meshes with ~10-µm diameter through-holes, called thin and tunable gas diffusion electrodes (GDEs), can reduce device thickness and decrease rare-element catalyst needs while increasing operating efficiency. GDEs can be fabricated through femtosecond (fs) pulsed laser micromachining of titanium (Ti) foil, where foil thickness, hole size, and fill factor can all be controlled. We present results from parametric studies of fs pulsed laser machining of thin (13 & 25 µm) Ti foils for GDE applications. Tightly focused fs laser pulses can rapidly machine small holes while significantly reducing collateral thermal damage. Direct control over surface chemistry is examined by modifying atmospheric conditions during machining to eliminate non-conductive oxidation, and heating during laser irradiation is observed with thermal micrography. Machined foil is characterized through optical and scanning electron micrographies and energy dispersive spectroscopy to determine resultant chemical species.