Bubble detection on the cathode and anode of a high-performing capillary-fed water electrolysis cell

The cathode and anode of a 'bubble-free' 'capillary-fed' water electrolysis cell that was previously reported to consume only 40.4 kW h 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, some bubbles were formed predominantly at the cathode up to & SIM;0.6 A cm(2). 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.