The hidden world inside rocks that could decide our energy future
Mohammad Hossein Khoeini defended his PhD thesis at the Department of Mechanical Engineering on March 31.
What happens on the invisible inner surfaces of rocks, filters, and catalysts largely determines whether technologies like COâ‚‚ storage, hydrogen production, and catalysis work efficiently and safely. The most important conclusion of this PhD research of Mohammad Hossein Khoeini is that a new, relatively fast experimental method based on inverse gas chromatography (IGC) can now measure the real chemical and structural diversity of porous surfaces at the scale of the whole material, rather than just small or simplified parts of it. This makes it possible to understand and design porous materials much more reliably for energy applications.
Porous materials are everywhere in energy technology. They are found in underground rock formations used for COâ‚‚ storage, in electrodes that help produce hydrogen, and in catalysts that speed up chemical reactions. What makes these materials so important is not just the holes inside them, but the surfaces within those holes. Fluids interact with these surfaces in different ways: sometimes they spread out, sometimes they stick, and sometimes they react. These interactions determine how fluids move, how reactions happen, and ultimately whether a technology works as intended.
The problem: real surfaces are not uniform
A major challenge is that the internal surfaces of porous materials are not uniform. Their chemistry and roughness change from place to place, meaning that fluids do not experience just one type of surface, but many different ones. Traditional measurement techniques struggle with this reality. Imaging methods can show where fluids are located but often miss chemical details at very small scales. Analytical methods can measure molecular interactions very precisely but often only for small or non-representative parts of the material. As a result, scientists and engineers often work with incomplete information about the very surfaces that control performance.
A new approach using molecular reporters
The PhD research of focuses on improving a technique called inverse gas chromatography. In this method, carefully selected gas molecules act as tiny reporters that travel through the porous material and interact with its surfaces. By observing how these molecules behave, researchers can learn about the surface properties throughout the entire accessible material. Instead of describing a surface as if it were one uniform material, the research shows that it is much more realistic to describe it as a combination of different regions, each with its own interaction strength and behavior.
Why this matters for the energy transition
By developing a method that can measure both chemical and structural surface differences across a whole sample, this research helps solve a long-standing problem in material characterization. The new methodology combines relatively fast experiments with an analytical framework that uses multicomponent adsorption measurements to reveal how heterogeneous a surface really is. This leads to a surface description that is both chemically detailed and representative of the full material. With this knowledge, engineers can design better catalysts and adsorbents, improve underground hydrogen storage, and better understand why materials lose performance over time. In this way, the research contributes to making key energy technologies safer, more efficient, and more predictable, which is essential for a sustainable energy future.
Title of PhD thesis: . Supervisors: Dr. Maja Rücker, Prof. David Smeulders, and Dr. Azahara Luna Triguero.