A team has created an efficient alkaline membrane electrolyser that closely rivals the performance of existing PEM electrolysers. This notable achievement is largely due to the use of affordable nickel compounds as the anode catalyst, which replaces the expensive and rare iridium.
In the future energy landscape, hydrogen is expected to be a key player, serving as a method for energy storage, a fuel, and a crucial raw material for the chemical sector. Hydrogen can be produced through water electrolysis in an almost climate-neutral manner, provided the electricity used comes from renewable sources like solar or wind. Currently, the development of a green hydrogen economy is primarily focused on two methods: proton-conducting membrane electrolysis (PEM) and traditional liquid alkaline electrolysis. Alkaline Membrane (AEM) electrolysers combine the benefits of both techniques and do not rely on rare precious metals like iridium.
Alkaline Membrane (AEM) Electrolysers Without Iridium
Recently, research teams from TU Berlin, HZB, the Department of Microsystems Engineering (IMTEK) at the University of Freiburg, and Siemens Energy have introduced the first AEM electrolyser capable of generating hydrogen with efficiency comparable to that of a PEM electrolyser. Instead of using iridium, they utilized nickel double hydroxide compounds combined with iron, cobalt, or manganese and devised a method to apply them directly onto an alkaline ion exchange membrane.
Understanding Molecular Processes in Electrolysis at BESSY II
During the electrolysis process, the team conducted operando measurements at the Berlin X-ray source, BESSY II, at the LiXEdrom end station. They collaborated with a theoretical team from Singapore and the USA to interpret the experimental results. ‘This allowed us to clarify the key catalytic-chemical processes occurring at the catalyst-coated membrane, particularly the phase change from a catalytically inactive alpha phase to a highly reactive gamma phase, as well as the involvement of various O ligands and Ni4+ centres in the catalysis,’ stated Prof. Peter Strasser from TU Berlin. ‘It is this gamma phase that enhances the competitiveness of our catalyst against the leading iridium catalysts. Our research indicates significant similarities to iridium’s catalytic mechanism, along with some intriguing molecular differences.’
This study has notably improved our understanding of the essential catalytic mechanisms associated with the new nickel-based electrode materials. Furthermore, the innovative coating technique for the membrane electrode indicates strong potential for scalability. A fully operational lab cell has already been tested at IMTEK. This work sets the groundwork for further industrial evaluation and shows that an AEM water electrolyser can indeed be highly efficient.
