Catalyst-Integrated Gas Diffusion Electrodes for Polymer Electrolyte Membrane Water Electrolysis: Porous Titanium Sheets with Nanostructured TiO₂Surfaces Decorated with Ir Electrocatalysts

Novel catalyst-integrated gas diffusion electrodes (GDEs) for polymer electrolyte membrane water electrolysis (PEMWE) cells are presented, in which porous titanium microfiber sheets are etched in NaOH to generate a nanostructured TiO2 surface, followed by arc plasma deposition (APD) of iridium nanoparticles. The porous titanium sheet acts as a gas diffusion layer (GDL); the nanostructured TiO2 surface acts as a catalyst support with large surface area; and the iridium nanoparticles act as the electrocatalyst. The performance of these unique GDEs in PEMWE cells was optimized by etching in different NaOH concentrations to vary the nanostructure of the TiO2; and by varying the Ir loading via the number of APD pulses. The current-voltage characteristics and the durability of the optimized GDEs were comparable to those reported in the literature using conventional Ir-based electrocatalysts, and electrolysis was achieved with current density up to 5 A cm-2. The main advantages of this catalyst-integrated GDE include the very low iridium loading (i.e. around 0.1 mg cm-2, or just one-tenth of the loading typically used in conventional PEMWEs); high electrolysis current density; the fabrication of stacks with fewer components; and the fabrications of thinner stacks. This could ultimately lead to smaller and lower cost PEMWE systems.