Manganese Photocatalyst Splits Water

Ideally, hydrogen fuel would come from splitting water rather than from processing oil. Direct electrolysis of water requires too much energy for large-scale applications, but photolysis—or splitting water with visible light—looks more promising. Mother Nature has optimized water oxidation by using a robust manganese-containing enzyme for photosynthesis. Taking inspiration from that enzyme, Leone Spiccia of Monash University, in Australia; G. Charles Dismukes of Princeton University; and colleagues have developed a manganese catalyst that can photooxidize water. The team previously synthesized a manganese-oxo cube core (Mn₄O₄) surrounded by diarylphosphinate ligands. Now, to give this insoluble compound access to water and to make it behave as a catalyst, the researchers have loaded the compound onto a commercially available proton-conducting Nafion polymeric membrane (Angew. Chem. Int. Ed., DOI: 10.1002/anie.200801132). They showed that when one of the ligands is released via activation with light, the catalyst carries out water oxidation for up to three days. The researchers suggest that their anodic half-cell could be paired with a solar-cell power source and a cathodic hydrogen-producing half-cell to construct a complete photoelectrochemical cell to make hydrogen fuel.