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Hydrogen is needed in abundance by mankind to achieve the transition away from fossil fuels. At the moment, green hydrogen (for fuel, heating and energy storage) is produced by splitting water using electricity for renewable sources. But what if hydrogen could be harvested directly from sunlight without the need for expensive electrolysis systems?

Plants achieve this chemical reaction naturally during photosynthesis using enzymes. In the structure of leaves, two molecules of water (H2O) are split into two oxygen (O2) molecules and four protons via an enzymatic process that traps electrons on a cluster bed of four manganese atoms, releasing H2O and O2.

Organic chemists at Julius-Maximilians-Universität Würzburg (JMU) have managed to recreate this catalytic reaction (dubbed Photosystem II) in the laboratory using a ruthenium centre (to replace manganese) in macrocyclic architecture – thereby serving the function of “artificial enzymes”.

"This success was made possible because our doctoral student Niklas Noll created an artificial pocket around the ruthenium catalyst. Therein, the water molecules for the desired proton-coupled electron transfer are arranged in front of the ruthenium centre in a precisely defined arrangement, similar to what happens in enzymes," comments the team leader Professor Frank Würthner, in a press release.

Ultimately, the idea is to design a water oxidation catalyst device that can be scaled up for use in agriculture and industry. Some of the pieces of the jigsaw puzzle are missing, but the first and most fundamental stage of the process has now been solved. The project has been funded by the European Research Council (ERC) and Bavarian Ministry of Science and Arts through the programme Solar Technology goes Hybrid.