Fabrication and Characterization of Nanoparticle Microporous Layers on Platinized Titanium Fiber Felt for Electrolyzer Anodes

Abstract

This study is concerned with the incorporation of various nanoparticles in the microporous layers (MPL) on titanium fiber felts for use at the anode in proton exchange membrane (PEM) water electrolyzers. The nanoparticle MPLs were coated onto Ti fiber felt using various methods. Three types of nanoparticles were utilized: indium tin oxide (ITO), tin (Sn) and titanium (Ti). The ITO and Sn nanoparticles were applied using an electrospraying technique, with Nafion as a binder (in the case of ITO) to ensure adhesion to the felt substrate and polyvinylpyrrolidone (PVP) as a surfactant to prevent nanoparticle sedimentation. This method resulted in uniformly smooth coatings. In contrast, Ti nanoparticles were deposited via a solvent evaporation method without a binder. This was followed by sintering of the nanoparticle-coated Ti felt at 750°C for 1 hour under an argon atmosphere. The resulting MPLs underwent comprehensive characterization, including surface imaging via scanning electron microscopy (SEM), assessments of permeability and porosity and measurements of electrical conductivity. The final and critical phase of characterization involved testing the samples in a laboratory-scale water electrolyzer. The electrolyzer setup included titanium bipolar plates with a once-through 2.1 x 2.1 cm – flow field leading to the membrane electrode assembly with an active area of 0.9 x 2.0 cm. All cells used to characterize performance consisted of a commercial carbon fiber cathode coated with an MPL (SGL 22BB) and a Hydrion N-115 catalyst-coated membrane. The tests revealed that the performance using sintered MPLs was superior to that of the electrosprayed MPLs and surpassed that of the baseline case (Ti felt with no coating). The sintered Ti coating with the lowest loading operated the best indicating that the rougher and thinner MPL was the best choice. The poor performance of the electrosprayed MPLs is attributed to the higher interparticle resistance due to the presence of non-conducting materials (dispersant and binder) as reflected in the lower conductivity of these MPL.