Sacrificial electron donor reagents for solar fuel production

Although justly considered as a cumbersome component in artificial photosystems, these simple molecules are a “necessary evil” to drive photo-induced reactions aiming at producing high added value molecules by photo-induced reduction of low energy value substrates. This review first presents the specifications of sacrificial electron donors. Then the various families of sacrificial donors used from the early 1970s to nowadays are reviewed, such as aliphatic and aromatic amines, benzyl-dihydronicotinamide (BNAH), dimethylphenylbenzimidazoline (BIH), ascorbic acid, oxalate and finally thiols. Experimental conditions (pH, solvent) are immensely versatile but important trends are given for adequate operation of a three-component system. Although literature abounds with various, very different artificial photosystems, we will realize that virtually the same sacrificial donors are used over and over again.