Omar Abdelrahman, corresponding author and an associate professor in the University of Houston Cullen College of Engineering’s William A. Brookshire Department of Chemical and Biomolecular Engineering, alongside Justin Hopkins, a chemical engineering Ph.D. student at the University of Minnesota, has introduced a technique that, for the first tim,e measures how fractions of an electron are shared between molecules and catalytic surfaces. The work demonstrates a method they call Isopotential Electron Titration (IET).
Hopkins, J. A., Page, B. J., Wang, S., Canavan, J. R., Chalmers, J. A., Scott, S. L., Grabow, L. C., McKone, J. R., Dauenhauer, P. J., & Abdelrahman, O. A. (2025). Isopotential Electron Titration: Hydrogen Adsorbate-Metal Charge Transfer. ACS Central Science. https://doi.org/10.1021/acscentsci.5c00851
The ability to quantify such small-scale electron transfer could reshape how catalysts are understood and designed. Catalysts are essential in industries ranging from fuels and chemicals to pharmaceuticals and batteries. They lower the energy barriers for reactions, improving efficiency and yield. For more than a century, chemists and engineers have theorized that partial electron sharing explains the effectiveness of precious metals like platinum, gold, and silver. Until now, these effects had not been measured directly.
The team built a catalytic condenser device, layering platinum on carbon with a thin dielectric separator above a silicon substrate. By holding the metal and substrate at the same potential, any electron movement caused by molecules binding to the platinum surface could be tracked as a measurable current. This setup allowed the group to quantify electron flow under realistic conditions of temperature and pressure, capturing values as small as fractions of a percent of an electron.
Omar Abdelrahman, associate professor at the University of Houston Cullen College of Engineering’s stated,
“IET allowed us to measure the fraction of an electron that is shared with a catalyst surface at levels even less than one percent, such as the case of a hydrogen atom on platinum. A hydrogen atom gives up only 0.2% of an electron when binding on platinum catalysts, but it’s that small percentage which makes it possible for hydrogen to react in industrial chemical manufacturing.”
In one demonstration, hydrogen atoms binding to platinum were found to donate only about 0.2 percent of an electron each. Despite the small value, that fractional transfer was enough to stabilize the reaction and explain platinum’s catalytic performance. The researchers confirmed their results against computational simulations, showing consistency between experimental data and theoretical models.
The technique has already been applied beyond hydrogen. In related work, the group measured electron transfer during ammonia adsorption on ruthenium, finding values of a few percent. This suggests IET can be used to study a wide range of catalyst–molecule interactions.
For engineering applications, the advance provides three potential benefits. First, it offers a measurable benchmark for electron transfer, helping researchers compare catalytic materials directly. Second, it creates a tool for screening and optimizing catalysts in development, potentially speeding up the discovery process. Third, it bridges experimental and computational approaches, allowing theory to be validated against tangible data.
Challenges remain. The measurements require specialized devices and extreme precision, as the signals are very small. Extending the method to complex real-world catalysts with multiple reaction steps will take further development. Still, the researchers believe that IET could establish a new foundation for catalytic science.
As Hopkins explained, measuring fractions of an electron under relevant conditions provides the clearest view yet of molecular interactions on catalyst surfaces. By turning a long-standing theoretical idea into a quantifiable parameter, the technique may help drive the next generation of catalytic technologies for energy, chemicals, and materials.
Adrian graduated with a Masters Degree (1st Class Honours) in Chemical Engineering from Chester University along with Harris. His master’s research aimed to develop a standardadised clean water oxygenation transfer procedure to test bubble diffusers that are currently used in the wastewater industry commercial market. He has also undergone placments in both US and China primarely focused within the R&D department and is an associate member of the Institute of Chemical Engineers (IChemE).
