Photocatalytic activity of CdS nanocrystals stabilized by a polymer shell and promoted by cobalt and nickel complexes in the reaction of hydrogen evolution

Nanocrystals (NCs) of CdS with oleate surface (NC-1) and octadecyl thiolate surface (NC-2), stabilized by a polycation shell, were doped with nickel bis(2-aminobenzenethiolate) (1), cobalt(III) chlorobis(dimethylglyoximato)(2-mercaptopyridine) (2), and also with 1,2-ethanedithiol and didodecylsulfide clathrochelates of cobalt(II) (3 and 4). The influence of doping on the photocatalytic activity in the hydrogen evolution reaction was investigated. Complex 1 appeared to be the most effective cocatalyst for H2 evolution with the reaction rate increased by the factor of 8—11. Accomodating the complex in a polymer shell yields the best result. The rate of H2 evolution increases monotonically with increasing concentration of this complex until the concentration achieves the ratio of one complex molecule per single NC. It is shown that the chemical composition of the surface has a significant influence on their photocatalytic activity in the hydrogen evolution reaction. The activity of NC-2 is 200 times that of NC-1. The replacement of oleate groups of the latter with sulfide increases the activity of these photocatalysts by a factor of 2000.