Researchers from the University of Oklahoma have pioneered a method to measure H₂ transfer energy in complex materials, paving the way for advancements in energy storage and renewable energy technology.

Published research led by OU doctoral student Nazmiye Gökçe Altınçekic used a technique called open-circuit potential to study energy changes within a hybrid material known as material-organic framework, or MOF. The MOF used in this research has a structure similar to titanium dioxide, a material widely used in energy applications. This was the first time open-circuit potential was used to measure energy changes in H₂ transfer reactions in this type of material.

“This type of reaction is needed to move from fossil fuels to more carbon-neutral fuel sources,” said Hyunho Noh, OU assistant professor and principal investigator of the study. “Furthermore, if we want to take carbon dioxide out of the atmosphere and turn it into useable fuel, then these findings are quite fundamental.”

According to Noh, the strength of a H₂ atom’s bond to a surface is key to its reactivity. He likens the desired bond strength to the Goldilocks principle.

“We don’t want the binding energy to be too low or too high. If the reactivity is too weak, the bond between the H₂ atom and the surface will never form. If it’s too strong, the H₂ atom will never leave the surface,” Noh said. “So, we want to tune the catalyst to be in the perfect range where it’s just strong enough to react, but not too strong that it can never leave.”

Previously, researchers have attempted to make these catalysts through trial-and-error, mixing and matching materials in hopes of finding the right combination. Altınçekic and Noh tried an alternate method. They first directly measured the binding energy of the MOF, then used that value as a basis to further tune the MOF for optimum value. Chance Lander, a fourth-year doctoral student, was then tasked with computationally predicting the reactions.

“We wanted to investigate if the placement of H₂ atoms on the MOF caused significant bonding impacts. By using computational chemistry, we were able to go step by step, testing multiple configurations, and observe what happens at the atomic level,” Lander said.

The team discovered that the binding energy of H₂ atoms and this MOF is quite different from what previously published research suggested. Results from the OU study demonstrate that by tuning the energy in these reactions, a library of titanium dioxide materials and their reactivities could be compiled. Doing so could potentially help future researchers create better materials for clean energy.

“We demonstrated that, even though the MOF and titanium dioxide looked identical, the binding energy of the two were very different. Is that because of the materials used? Is it because this specific connectivity gives us this specific value? That’s for future research to decide, but it is exciting,” Noh said.