Non-precious bifunctional oxygen catalysts for regenerative seawater electrolyzers

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The intermittency of ever increasing renewable solar and wind energy capacities drives up demand for more and more suitable molecular energy storage. Hydrogen, made of electricity and water, is regarded the most promising energy storage molecule. Today, water splitting is carried out using fresh water. Much more desirable would be the efficient electrochemical splitting of raw saline sea water. Reversible seawater electrolyzers, i.e. assemblies that split seawater in hydrogen as well as convert the hydrogen in electricity and freshwater, will enable a self-sufficient energy and fresh water supply in seawater near desert regions. For that purpose new suitable bifunctional electrocatalysts for reversible hydrogen- and oxygen-electrodes are required. Such catalysts have not been explored yet. This will be investigated within the framework of this project. The overall goal is the identification and molecular understanding of structure activity relationships of novel non precious bifunctional catalyst for regenerative seawater splitting in reversibly operating membrane-based electrolyzers. To achieve this goal this project will explore the concept of two-component-catalyst systems as a way to generate special active sites at the surface of the hybrid material, where each component will be specialized to either the selective seawater splitting or the conversion of hydrogen in electricity and fresh water. Own prior results have shown that such hybrid materials exhibit outstanding bifunctional activity. Molecular mechanisms and limitations of this materials concept, however, are still unclear. To address this, electrochemical activity and stability investigations will be combined with structural analysis to develop structure-, reactivity- and stability-relationships for reversible catalyst systems. Special Emphasis will be put on enhanced chloride corrosion and molecular degradation. New fundamental materials insights will be verified in a single cell reversible electrolyzer assembly. Thereby, additional new knowledge about the alkaline ionomer-catalyst-reactant three-phase boundary and their stabilities will be generated. The broad analytical method portfolio of this project targeting structure, charge transport, electrocatalytic stability and activity will provide fundamental understanding, yet will also yield a first sense of how such hybrid catalyst perform in more complex electrolytic environments. In all this project is a fundamental contribution to the Materials Science of renewable energy storage.