Renewable, or green, hydrogen will play a critical role in the decarbonisation of hard-to-abate sectors and will therefore be important in limiting global warming. However, renewable hydrogen is not cost-competitive with fossil fuels, due to the moderate energy efficiency and high capital costs of traditional water electrolysers. Here a unique concept of water electrolysis is introduced, wherein water is supplied to hydrogen- and oxygen-evolving electrodes via capillary-induced transport along a porous inter-electrode separator, leading to inherently bubble-free operation at the electrodes. An alkaline capillary-fed electrolysis cell of this type demonstrates water electrolysis performance exceeding commercial electrolysis cells, with a cell voltage at 0.5 A cm−2 and 85 °C of only 1.51 V, equating to 98% energy efficiency, with an energy consumption of 40.4 kWh/kg hydrogen (vs. ~47.5 kWh/kg in commercial electrolysis cells). High energy efficiency, combined with the promise of a simplified balance-of-plant, brings cost-competitive renewable hydrogen closer to reality.

No abstract

‘Green’ hydrogen produced from water electrolysis powered by renewable energy will play a critical role in the future global energy transition to ‘net zero’ carbon emissions. To this end, intensive...

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.