Frequency Analysis of Water Electrolysis Current Fluctuations in a PEM Flow Cell: Insights into Bubble Nucleation and Detachment

A cross-shaped transparent electrolysis flow cell was designed to simultaneously perform polarization experiments to about 2 A cm −2 while monitoring the current response due to bubble formation and detachment. The flow cell was designed in order to accommodate a large electrolyte flow and have flow conditions similar to a PEM electrolyzer. Ir foil experiments using rapid electrochemical cycling techniques were performed first as a quality control measure for cell functionality. Literature quality cyclic voltammograms were obtained, with the anodically formed iridium oxide film growth plateauing after 1000 cycles. The performance of four different Ti current collector meshes were evaluated using a commercial IrO 2 CCM using 3.5 M H 2 SO 4 at 21 ± 0.5°C. The best performing current collector mesh had the largest triple-phase boundary (TPB) length of 56 mm and a porosity of 52%. Using Fourier Transform analysis, the bubble ratios for different current collector and frequency regimes were obtained. The lowest frequency bubble analysis (< 1 Hz) showed the best correlation with the performance of the different meshes.