German Researchers Develop Alkaline Membrane Electrolyzer
A team of researchers in Germany have developed a highly efficient alkaline membrane electrolyser, which is designed to match the performance of established PEM electrolysers.
Its anode catalyst consists of inexpensive nickel double hydroxide compounds with iron, cobalt or manganese. The water electrolyser cell works with a newly developed membrane electrode unit that is directly coated with a layer-structured nickel-based anode catalyst.
Researchers from the TU Berlin, the Helmholtz Center Berlin, the Institute of Microsystems Technology (IMTEK) at the University of Freiburg and Siemens Energy presented it in the journal “Nature Catalysis.”
“Recent efforts in the field of anion exchange membrane water electrolysis focus on developing superior catalysts and membrane electrode assemblies to reduce the performance gaps compared to proton exchange membrane water electrolysis,” the researchers stated.
Instead of iridium, they used nickel double hydroxide compounds with iron, cobalt or manganese and developed a process to directly coat an alkaline ion exchange membrane with them. The new electrolyzer should produce hydrogen almost as efficiently as a PEM electrolyzer.
The researchers used the Berlin Bessy II X-ray source to carry out operando measurements in the cell during electrolysis. The experimental data were then interpreted with the help of a theory team from Singapore and the US.
“This enabled us to clarify the relevant catalytic-chemical processes on the catalyst-coated membrane — in particular the phase transition from a catalytically inactive alpha phase to the highly active gamma phase and the role that the various O ligands and Ni4+ centers play in catalysis,” said Peter Strasser from the TU Berlin.
It is this gamma phase that makes the new catalyst competitive with current iridium catalysts. “Our work shows important similarities to iridium in the catalytic mechanism, but also completely surprising molecular differences,” Strasser continued.
The study has significantly expanded the understanding of the fundamental catalytic mechanisms of the new nickel-based electrode materials.
According to the researchers, the newly developed coating process for the membrane electrode promises very good scalability.
A first fully functional small cell has already been tested at IMTEK. This lays the foundation for an industrial evaluation and the researchers have demonstrated that an AEM water electrolyzer can also be highly efficient.
