Self-Optimizing Cobalt-Tungsten Catalysts for Efficient Hydrogen Production

Researchers from Johannes Gutenberg University Mainz have developed water-splitting catalysts that are both cost-effective and efficient for hydrogen production. The efficiency of these catalysts improves over time.

Hydrogen is considered a promising alternative for producing CO₂-neutral energy. Electrolyzer devices, which separate water into oxygen and hydrogen, are powered by renewable energy sources, primarily solar and wind power.

Catalysts are needed to facilitate the process. Currently, benchmark catalysts are noble metal oxides like iridium dioxide and ruthenium dioxide. These metals are expensive, rare, and unstable in both alkaline and acidic conditions.

Dr. Dandan Gao, a junior group leader at Johannes Gutenberg University Mainz (JGU) and recipient of a Walter Benjamin Fellowship from the German Research Foundation, along with colleagues, has developed an alternative catalyst using affordable and easily accessible cobalt and tungsten.

What's so unique about our catalyst is that it actually enhances its performance over time, while conventional catalysts either maintain their performance at a consistent rate or even lose some of their performance because they are insufficiently durable. After the process of optimization, activity is even higher than that of benchmark catalysts.

Dr. Dandan Gao, Johannes Gutenberg University Mainz (JGU)

What Causes the Self-Optimization Process?

The researchers conducted both theoretical and experimental studies to explain the catalyst's self-optimization. They found that the cobalt-tungsten oxide catalyst undergoes a chemical transformation during the water-splitting process. Initially, the cobalt is mostly in the Co²⁺ state, but it gradually changes to Co³⁺. Meanwhile, the percentage of the original tungsten W⁵⁺ ion shifts in favor of the W⁶⁺ ion.

There are two reactions during the splitting of water. The hydrogen evolution reaction (HER), which produces hydrogen gas, and the oxygen evolution reaction (OER), which produces oxygen gas. The OER represents the bottleneck for the whole reaction. That's why we are so committed to developing a catalyst that can promote the OER half-reaction.

Dr. Dandan Gao, Johannes Gutenberg University Mainz (JGU)

Over time, the mechanism shifts to the cobalt active site, although the tungsten active site initially induces the oxygen evolution reaction (OER). The catalyst's electrochemically active surface area also increases over time. Additionally, the researchers observed changes in the surface's hydrophilicity. Its increasing affinity for water is particularly beneficial for electrochemical water-splitting.

“In general, we recorded notably reduced overpotentials and increased current densities accompanied by a substantial increase in OER kinetics,” concluded Gao.

These findings are promising for the future of hydrogen production.

Funding by the Walter Benjamin Program of the German Research Foundation

Dandan Gao has been supported since June 2023 by the German Research Foundation (DFG) under the Walter Benjamin Program. This program allows early career researchers to work on their projects at any university. The project is supported by Johannes Gutenberg University Mainz, the host research institution.

Additionally, the work has received support from JGU's Top-level Research Area SusInnoScience – Sustainable Chemistry as the Key to Innovation in Resource-efficient Science in the Anthropocene, the Alexander von Humboldt Foundation, and the Carl Zeiss Foundation.

Journal Reference:

Nickel, C., et al. (2025) Self-optimizing Cobalt Tungsten Oxide Electrocatalysts toward Enhanced Oxygen Evolution in Alkaline Media. Angewandte Chemie International. doi.org/10.1002/anie.202424074