Processes for transporting green hydrogen become more productive

Researchers at the Friedrich-Alexander-Universit├Ąt Erlangen-Nuremberg (FAU) and the Helmholtz Institute Erlangen-Nuremberg for Renewable Energies (Hi Ern) have now found that catalyst productivity for gas generation reactions can be significantly increased if the catalyst pores are particularly easily formed gas bubbles. This extra element, which significantly affects reaction time, was previously unidentified.

According to Prof. Dr. Peter Wasserscheid, head of the Chair of Chemical Reaction Engineering at FAU and director of the Helmholtz Institute Erlangen-Nuremberg, a division of Forschungszentrum J├╝lich, “Up until now, it was thought that the speed was only determined by the chemical surface reaction or by the transport of the molecules to the active centers of the catalyst.”

The discovery was based on a process that may be crucial in the future transportation of green hydrogen. Liquid organic hydrogen carriers, or LOHCs, are used to store, transport, and then release hydrogen that has been bound to them. The technology is regarded as being very user-friendly and safe. The method is more portable and potent when hydrogen can be liberated from the carrier medium with the aid of a catalyst quickly.

The scientists were able to demonstrate that, under the same circumstances, if the development of gas bubbles in the pores of the catalyst is promoted, 50 times more hydrogen is removed from the carrier medium per unit of time. The reason for the striking disparity is: “Normally, only the catalytic hydrogen release results in the system producing dissolved hydrogen. The liquid phase then quickly becomes saturated in the vicinity of the catalyst’s active sites, according to Peter Wasserscheid.

On the other hand, the bubbles in the catalyst pores function as small pumps. They aid in releasing the hydrogen and dispersing it. “The rising bubble catches the hydrogen that has been produced once a bubble has formed in a catalyst pore. According to Peter Wasserscheid, the process restarts when the bubble bursts into the surrounding liquid and divides into the charged hydrogen carrier.

Nucleation, the scientific word for the development of bubbles, can also be induced artificially through the use of a mechanical stimulus or chemical modification of the catalyst surface. The results provide new insight into performance-limiting elements in heterogeneous catalysis, which are crucial for the development of a sustainable hydrogen economy.

The findings, which have just been published in the prestigious journal Science Advances, were generated in partnership with the teams of professors Jens Harting, Matthias Thommes, Nicolas Vogel, and Peter Wasserscheid in the DFG Collaborative Research Center 1452 “Catalysis at Liquid Interfaces.”