2/13/2026 Jeni Bushman
Engineers led by Assistant Professor Yingjie Zhang have developed a groundbreaking three-state model that reveals how water molecules behave at solid surfaces, resolving decades of scientific debate about the nature of these critical interfaces. By combining advanced microscopy techniques, the research provides a molecular blueprint that enables precise control of solid-water boundaries, with transformative implications for water desalination, carbon dioxide reduction and electrochemical energy storage technologies.
Written by Jeni Bushman
Illinois Grainger engineers have combined two ultra-sensitive techniques to explain the behavior and characteristics of molecular environment at the graphite-water interface.
For decades, a fundamental question has lingered at the intersection of physics and chemistry: What does the molecular environment look like where water meets a solid? This tiny boundary, called the interface, drives the most critical actions of many modern technologies. Scientists have long debated the true nature of this interface, unsure if it is truly pristine or contains impurities like hydrocarbons and dissolved gas molecules.
Now, researchers from the lab of Yingjie Zhang, an assistant professor of materials science and engineering, have finally decoded this molecular landscape. In collaboration with the Instituto de Ciencia de Materiales de Madrid and published in Nature Communications, the group’s unique three-state model explains how different factors influence the behavior of water molecules at the graphite-water interface. Their findings enhance scientists’ understanding of the molecular blueprint used for water desalination, carbon dioxide reduction, and many other electrochemical applications.
“Water in the bulk is very different from water at the interface, and its structure determines if and how reactant molecules will participate in certain reactions,” said Lalith Bonagiri, a graduate student and lead co-author of the paper. “Understanding the interfacial water network is crucial for many fields.”
But settling an age-old debate is no easy task; to tackle this particular challenge, Zhang’s lab probed the molecular structure of water interfaces using two ultra-sensitive techniques: 3D atomic force microscopy (3D-AFM) and a specialized type of Raman spectroscopy called SHINERS. This dual approach revealed that the interface is not a single static structure, but a dynamic three-state system. Using the graphite-water interface as an experimental framework, the Illinois Grainger engineers’ model explains the interfacial microenvironment with unprecedented clarity.
When water first touches a freshly prepared graphite surface, it enters State 1— a transient phase dominated by pristine water molecules with severely disrupted hydrogen bonds near the surface. Microscopic contaminants quickly begin to crowd this formerly pristine water, a transition Zhang and his colleagues categorize as State 2. They believe this contaminated state explains why many previous experiments failed to capture pristine water structures.
The model’s final phase, State 3, occurs when a negative electric voltage is applied to graphite. This voltage acts as a molecular vacuum cleaner, repelling contaminants and attracting pristine water back to the surface. In this electrified state, water organizes into a stable, diverse network of hydrogen bonds that can be precisely controlled. Ultimately, this discovery acts as a dial, allowing scientists to control the interface.
“By resolving these long-standing controversies within this model system, we have provided a universal configuration diagram that tracks how surface charge and environmental aging transform the solid-water boundaries,” Bonagiri said. “Our three-state blueprint can extend far beyond graphite to a vast array of industrially relevant materials, including metals and semiconductors.”
The study’s impact is two-fold, introducing a powerful new method for precisely capturing solid-liquid interfaces and providing foundational data that can be used in future materials developments.
“The ability to identify the realistic structure of solid-water interfaces is crucial for the rational design of systems like electrochemical energy storage and photocatalysis," Zhang said. “By correlating physical spatial mapping with chemical identification, we finally have the ‘eyes’ to see the molecular environment where solids and liquids meet.”
Illinois Grainger Engineering Affiliations
Yingjie Zhang is an Illinois Grainger Engineering assistant professor in the Department of Materials Science and Engineering. Zhang is affiliated with the Materials Research Lab and the Beckman Institute for Advanced Science and Technology.