Minimising the ohmic resistance of an alkaline electrolysis cell through effective cell design

Abstract The efficiency of an alkaline electrolysis cell depends strongly on its internal cell resistance, which becomes the dominant efficiency driver at high current densities. This paper uses Electrochemical Impedance Spectroscopy to decouple the ohmic resistance from the cell voltage, and, for the first time, quantify the reduction in cell resistance achieved by employing a zero gap cell configuration when compared to the conventional approach. A 30% reduction in ohmic resistance is demonstrated for the zero gap cell when compared to a more conventional design with a 2 mm electrode gap (in 1 M NaOH and at standard conditions). The effect on the ohmic resistance of operating parameters, including current density and temperature, is quantified; the zero gap cell outperforms the standard cell at all current densities, particularly above 500 mA·cm −2 Furthermore, the effect of electrode morphology on the ohmic resistance is investigated, showing that high surface area foam electrodes permit a lower ohmic resistance than coarser mesh electrodes. These results show that zero gap cell design will allow both low cost and highly efficient alkaline electrolysis, which will become a key technology for short term and inter-seasonal energy storage and accelerate the transition towards a decarbonised society.