Researchers at the University of Amsterdam (UvA) have made a groundbreaking discovery in an endeavor, utilizing flexible spheres of the biomolecule chitosan derived from shrimp waste to develop catalysts for generating hydrogen gas from borohydride salts.
In a paper published in Green Chemistry, the UvA research team demonstrates the spheres’ ability to “breathe out” hydrogen bubbles without breaking, a significant advancement towards practical and secure hydrogen storage and release systems.
The UvA’s Heterogeneous Catalysis & Sustainable Chemistry group has been working on utilizing alkali metal borohydride salts as potential hydrogen carriers since 2020. These solid salts offer a safe means of hydrogen storage under ambient conditions and release hydrogen gas only when they react with water. However, managing the controlled release of hydrogen to prevent runaway reactions has proven challenging.
To stabilize the solution and control hydrogen release, the UvA team is developing catalysts in collaboration with the Austrian Competence Centre for Tribology (AC2T) and Electriq Global. Traditional catalysts, however, face rapid destruction due to the combination of high reaction pH and continuous hydrogen bubble release.
A breakthrough occurred when MSc student Jeffrey Jonk and Ph.D. student Fran Pope decided to encapsulate cobalt particles in chitosan spheres. Chitosan, a natural polymer obtained from chitin found in insect exoskeletons and crustacean shells, proved to be an ideal candidate. These biodegradable and biocompatible spheres could be produced by dropping liquid chitosan into a basic solution. Crucially, the spheres’ flexibility allows them to expand during hydrogen generation, releasing hydrogen bubbles without breaking. Additionally, since they are made at high pH, they are unaffected by the basicity of the borohydride solution.
The new catalysts were tested in batch and continuous modes, showcasing their potential in generating hydrogen. A few millimeter-sized spheres containing 7% cobalt produced an impressive 40 mL of hydrogen per minute in a continuous reactor for two days, demonstrating the real-life viability of this innovative catalyst.
According to Prof. Gadi Rothenberg, the leader of the research team, the focus on catalyst stability is paramount. While many papers highlight catalyst activity and selectivity, true viability lies in a catalyst’s ability to perform efficiently for extended periods. Only catalysts that prove economically viable on a large scale, working for months and years, will drive the future of sustainable hydrogen storage solutions.
The novel application of chitosan spheres as catalyst stabilizers opens new doors for green hydrogen storage and release. This discovery represents a significant stride in making hydrogen a reliable and practical energy carrier, contributing to a sustainable energy transition. As research continues, chitosan-based catalysts offer promising potential in shaping the future of hydrogen technologies, bringing us closer to a cleaner and greener world.
