Bubble Detection on the Cathode and Anode of a High-Performing Capillary-Fed Water Electrolysis Cell

Abstract

The cathode and anode of a ‘bubble-free’ ‘capillary-fed’ water electrolysis cell that was previously reported to consume only 40.4 kWh kg-1 hydrogen under standard commercial operating conditions, have been separately investigated for the incidence of gas bubble formation during operation. Adaptions of a voltage fluctuation and an acoustic emission technique were applied in combination, to detect and analyze bubble formation at current densities up to 1 A cm-2. The two techniques produced very similar results, showing little bubble formation up to 0.17-0.20 A cm-2. Thereafter, bubbles were formed predominantly at the cathode up to ~0.6 A cm2. At higher current densities, the cathode and anode produced bubbles at similar rates, that were substantially lower than in conventional, ‘bubbled’ electrolysis cells. In the course of this work, the previously reported high electrochemical performance of the capillary-fed cell was independently confirmed.

Operando monitoring of gas bubble evolution in water electrolysis by single high-frequency impedance

“…Given that the HER produces more gas products and faster but with smaller size of hydrogen bubbles, the resistance variation at the cathode is expected to have a slightly bigger impact on the overall dynamic resistance variation, which is similar to detecting more hydrogen gas bubbles on cathodes via voltage signal noise and acoustic emission techniques. 39 However, the FFT patterns of bare NF and Ni(OH) 2 /NF electrodes in an alkaline electrolyser full-cell show more similar amplitudes to those recorded during the OER at increased potentials in the three-electrode half-cell, and notably smaller than the FFT patterns of these electrodes during the HER. This could be due to the cancellation effect of the combined noises and fluctuations at the anode and cathode.…”