(Invited) Alkaline Water Electrolysis: Achieving High Current Densities

The production of hydrogen via water electrolysis is currently recognized as the only option to store gigawatt electrical energy coming from renewable energy sources such as wind and sunlight. However, commercially available alkaline electrolyzers are still limited to low current densities (around 0.5 Acm-2), primarily due to its internal resistance losses. In order to reach the excellent current densities of acidic polymer electrolyte membrane (PEM) water electrolysis (ranging between 2 and 4 Acm-2), it is crucial to tailor electrolyte construction and cell design in order to overcome the high ohmic losses of conventional diaphragms and archaic cell designs used in alkaline electrolysis. Here, we demonstrate for the first time alkaline electrolysis achieving current densities as high as 2 A.cm-2 at 2 volts, not only well overcoming the performances of lab-scale and commercial alkaline electrolyzers, but also closely matching the performance of state-of-the-art PEM water electrolysis.