Photoproduction of hydrogen by decamethylruthenocene combined with electrochemical recycling

The photo-induced hydrogen evolution reaction (HER) by decamethylruthenocene, Cp2*Ru(II), is reported. The use of a metallocene to photo-produce hydrogen is presented as an alternative strategy to reduce protons without involving an additional photosensitizer. The mechanism was investigated by (spectro)electrochemical and spectroscopic (UV/vis and 1H NMR) measurements and the photo-activated hydride involved was characterized spectroscopically and the resulting [Cp2*Ru(III)]+ species was electrochemically regenerated in situ on a Fluorinated Tin Oxide (FTO) electrode surface. A promising internal quantum yield of 25 % was obtained. To complete this investigation, optimal experimental conditions, especially the use of weakly coordinating solvent and counter ions, are discussed.