Self-templated synthesis of nanoporous CdS nanostructures for highly efficient photocatalytic hydrogen production under visible light

Nanoporous CdS nanostructures, including nanosheets and hollow nanorods, have been prepared by a two-step aqueous route, which consists of a first precipitation of nanoporous Cd(OH)₂ intermediates and a subsequent S^2-/OH^- ion-exchange conversion of the obtained Cd(OH)₂ used as template either to nanoporous CdS nanosheets with sizes up to 60 nm and an average thickness of about 9 nm or to CdS hollow nanorods with lengths up to 30 nm and outer diameters in the range 7-14 nm. The obtained CdS nanostructures containing nanopores with diameters of ∼3 nm exhibit a very large BET surface area of about 112.8 m² g ^-1. A very high hydrogen yield of about 4.1 mmol h^-1 under visible light irradiation (λ ≥ 420 nm), corresponding to the highest apparent quantum yield of about 60.34% measured at 420 nm so far reported, has been attained over the obtained nanoporous CdS nanostructures loaded with monodisperse 3-5 nm Pt nanocrystals, which is due to an efficient charge separation, a fast transport of the photogenerated carriers, and a fast photochemical reaction at the CdS/electrolyte interface. The photocatalytic reaction conditions, such as the Pt-loading content, the amount of catalyst, and the concentration of sacrificial regents, have been optimized.