麻豆淫院

Hydrogen is a much-debated option in terms of CO鈧�-neutral energy production. Electrolyzer units that split water into its constituent oxygen and storable hydrogen are supplied with electricity from renewable resources, mainly generated by wind and solar energy. However, catalysts are necessary to facilitate this process. To date, noble metal oxides such as ruthenium dioxide and iridium dioxide are being used as benchmark catalysts. These metals, however, are expensive, rare, and unstable in both acidic and alkaline environments.

Dr. Dandan Gao, a junior group leader at Johannes Gutenberg University Mainz (JGU) and holder of a Walter Benjamin Fellowship sponsored by the German Research Foundation, and her team have managed to devise an alternative form of catalyst using cobalt and tungsten, elements that are readily available at low cost.

"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," stated Dr. Dandan Gao. "After the process of optimization, activity is even higher than that of benchmark catalysts." The results of Gao and her team have recently been in the journal Angewandte Chemie International Edition.

What causes the self-optimization process?

The researchers undertook experimental and theoretical investigations to find an explanation for the extraordinary self-optimization of their catalyst. They were able to determine that the chemical nature of the catalyzing cobalt-tungsten oxide changes during the process of water-splitting. While the cobalt is initially largely present in the form of Co虏鈦�, it is increasingly converted to Co鲁鈦�.

At the same time, the proportion of the original tungsten W鈦碘伜 ion to the W鈦垛伜 ion shifts in favor of the latter. "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," explained Gao. "That's why we are so committed to developing a catalyst that can promote the OER half reaction."

While the OER is initially induced by the tungsten active site, this process is transferred with time to the cobalt active site. Moreover, the electrochemically active surface area of the catalyst also increases over the course of time. The research team also observed alterations to the hydrophilicity of the surface. Its affinity for water increases progressively, which is particularly beneficial in the context of electrochemical water-splitting.

"In general, we recorded notably reduced overpotentials and increased current densities accompanied by a substantial increase in OER kinetics," concluded Gao. All this is positive news for the hydrogen production of the future.