Keeping water connected helps carbon electrodes last longer

The University of Osaka

Osaka, Japan – Carbon is inexpensive, conductive, and widely used in technologies such as fuel cells and water electrolyzers. But under strongly oxidizing conditions, carbon electrodes gradually corrode. Researchers at the University of Osaka and their international collaborators have now found that the arrangement of water molecules directly next to the electrode plays a key role in this degradation, suggesting a new way to improve durability.

By monitoring both carbon corrosion and interfacial water during operation, the researchers found that corrosion accelerated as the network connecting nearby water molecules became more disrupted. Weakly connected water appeared to be preferentially involved in the oxidation of carbon to carbon dioxide, and deliberately disturbing the network further increased corrosion.

Rather than modifying the carbon itself, the team then changed its immediate environment. They used different ion-conducting polymers, known as ionomers, to reorganize water at the electrode surface. Sustainion created a more strongly connected water network than the commonly used Nafion and reduced carbon corrosion by about 51%.

The researchers next tested the concept in a chlorine-producing system using a carbon-supported platinum catalyst. Although Sustainion improved durability, it initially reduced catalytic activity. By combining Sustainion with Nafion, the team retained high initial activity while limiting performance loss to 19% after 500 cycles.

“Electrodes are often considered the main players in electrochemical reactions, but the water immediately surrounding them is also important,” says Dr. Yu Katayama, one of the corresponding authors at the University of Osaka. “Our results show that designing the environment around an electrode, not only the electrode material itself, could help improve its durability.”

The findings highlight control of interfacial water as a promising design principle for carbon electrodes and could contribute to longer-lasting electrochemical technologies, including green hydrogen production, chlorine manufacturing, and fuel cells.