Researchers at the University of Amsterdam have found a way to protect their hydrogen-releasing cobalt catalyst from degradation: flexible, porous spheres made from shrimp waste.
A practical challenge in creating a hydrogen economy is the safety risk posed by high-pressure and liquid hydrogen. An alternative is to store hydrogen in a salt, such as potassium borohydride (KBH4), and then release it in a controlled manner through a catalysed reaction with water. There are many metals and oxides that catalyse this reaction, but the stability of the catalyst during the reaction is still an issue, because the high pH and hydrogen bubbles formed during the reaction cause the catalyst to degrade rapidly.
Researchers at the Van ’t Hoff Institute for Molecular Sciences at the University of Amsterdam have found a way to counteract this degradation. They encapsulated their cobalt catalyst in flexible, porous spheres made of chitosan, which is found in shrimp and crab shells. These spheres can expand when the hydrogen bubbles form, and shrink again when the hydrogen bubbles have escaped. The spheres are produced at high pH. This ensures that they remain intact under the desired reaction conditions. The researchers have published their results in Green Chemistry.
’It was really a so-called Friday afternoon experiment,’ says Gadi Rothenberg, co-author and professor of heterogeneous catalysis and sustainable chemistry. ’My students Jeffrey Jonk and Frances Pope had read something they wanted to try, and it worked. Doing unorthodox research from time to time is part of good scientific research.’ He stresses that the key insight is the principle: a flexible shell for the catalyst and the combination of mechanical and chemical degradation.
According to Rothenberg, the catalyst is not yet good enough for industrial use, but it is a step in the right direction. It still needs a lot of development, but it is cheap enough to have potential. ’That is a very important parameter. The industry is focused on making money, and to do that catalysts have to work for a long time. They will only use a new catalyst if they are sure it will work as well as the ones they already have.’ He is developing the catalyst in collaboration with the Austrian Competence Centre for Tribology and the company Electriq Global.
Pope et al. (2023) Green Chemistry https://doi.org/10.1039/D3GC00821E