Science, one of the world’s leading scientific journals, has published an article co-authored by a professor with the University of Houston Cullen College of Engineering that uncovers how hydrogen moves along an iron oxide surface when in the presence of water. The findings could have implications for everything from hydrogen storage to catalysis to fuel cell-powered vehicles.
The paper, which appears in the publication’s May 18 issue, was co-written by Lars Grabow, assistant professor of chemical and biomolecular engineering.
According to Grabow, it has long been assumed that water encourages the diffusion, or movement, of hydrogen across metal oxide surfaces. Exactly why this is has only been theorized, until now. Grabow and his collaborators found that on a thin film of iron oxide a water molecule essentially passes along hydrogen protons from one surface site to another, briefly forming an H3O,+ molecule in the process.
Discovering this required simulations to help reveal the mechanisms behind hydrogen diffusion as well as experiments observed with advanced microscopy techniques.
Grabow’s expertise lies on the simulation side, specifically in density functional theory (DFT), which uses quantum chemistry to predict reactions on the level of individual atoms. Using DFT, Grabow, “developed the computational model system and figured out a way to perform these simulations on large systems.” The findings of these simulations are in agreement with high-speed scanning tunneling microscopy, which allowed the researchers to observe the movement of hydrogen at atomic resolution by scanning individual lines in just 18 milliseconds.
According to Grabow a better understanding of how hydrogen interacts with metal oxides could impact numerous fields. Research involving electrochemical water splitting for hydrogen production and fuel cell vehicles in particular could benefit. Knowing how these metal oxides interact with hydrogen could allow for the creation of more efficient electrodes on both the anode and cathode size of a cell, Grabow said. What’s more, understanding hydrogen movement across these surfaces could allow for the creation of safe, affordable hydrogen storage systems for fuel-cell powered vehicles.
“People don’t feel comfortable driving around in a car with a pressurized hydrogen container,” said Grabow. “Some sort of safe, solid phase hydrogen storage material that allows you to transfer the hydrogen in and out quickly and easily is an important potential application.”
Grabow’s co-authors on this piece include the senior authors Flemming Besenbacher from Denmark’s Aarhus University and Manos Mavrikakis from the University of Wisconsin-Madison; first author Lindsay Merte, Ralf Bechstein, Felix Riebolt, Eric Laesgaard, Wilhelmine Kundernatsch and Stefan Wendt, all with Aarhus; as well as Winsconsin’s Guowen Peng and Carrie Farberow.