Preparation procedure for the electrode slurries of polymer electrolyte fuel cells utilizing the irreversibility of ionomer adsorption onto Pt–C particles

The effect of slurry preparation for polymer electrolyte fuel cells on the electrode performance has been investigated in this work. The amount of ionomer adsorbed onto Pt–C powder increases when water is used as a solvent; however, the size of non-adsorbed ionomer particles increases as well, resulting in a larger gas permeation resistance. Meanwhile, increasing the ethanol-to-water mass ratio in a mixed solvent decreases the ionomer size. Therefore, an improved two-step slurry preparation procedure utilizing the irreversibility of the ionomer adsorption onto Pt–C powder has been investigated. In this method, (1) Pt–C powder is mixed with ionomer in water to maximize its adsorbed fraction, after which (2) ethanol is added to the prepared slurry to minimize the size of non-adsorbed ionomer. As compared with the conventional one-step synthesis method, the developed two-step preparation procedure enhances the electrode performance without changing its composition.