Photochemical water splitting mediated by a C1 shuttle.

The possibility of performing photochemical water splitting in a two-stage system, separately releasing the H2 and O2 components, has been probed with two separate catalysts and in combination with a formaldehyde/formate shuttling redox couple. In the first stage, formaldehyde releases hydrogen vigorously in the presence of an Na4[Fe(CN)6]·10H2O catalyst, selectively affording the formate anion. In the second stage, the formate anion is hydro-genated back to formaldehyde by water and in the presence of a Bi2WO6 photocatalyst whilst releasing oxygen. Both stages operate at room temperature and under visible light irradiation. The two separate photocatalysts are compatible since water splitting can also be obtained in one-pot experiments with simultaneous H2/O2 evolution.