Self-Templated Synthesis of Nanoporous CdS Nanostructures for Highly Efficient Photocatalytic Hydrogen Production under Visible Light

Abstract

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-/OHion-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 m 2 g -1 . A very high hydrogen yield of about 4.1 mmol h -1 under visible light irradiation (λ g 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.

Roles of cocatalysts in semiconductor-based photocatalytic hydrogen production

“…Bao et al [18] realized a QE of about 60 per cent at 420 nm for H 2 evolution from Na 2 S/Na 2 SO 3 solution by loading 13 wt% of Pt on nanoporous CdS. The activity depends on the Pt-loading content, the amount of catalyst and the concentration of sacrificial regents, and was attributed to an efficient charge separation, a fast transport of the photogenerated carriers and a fast photochemical reaction at the CdS/electrolyte interface [18]. Subsequently, we reported a QE of 50 per cent at 420 nm for H 2 evolution from Na 2 S/Na 2 SO 3 solution on CdS synthesized by a hydrothermal method through loading less than 1 wt% of Pt [11].…”

“…A main shortcoming for CdS (and other sulfide or nitride semiconductors) photocatalyst is the photo-instability, which is owing to photocorrosion (CdS + 2h + → Cd 2+ + S) [18]. The reaction time courses (figure 5) for H 2 evolution showed that the rate of H 2 production over Pt/CdS gradually decreases and an evident drop in the activity is found after an irradiation for 7 h [11].…”

Controlled Fabrication of Colloidal Semiconductor–Metal Hybrid Heterostructures: Site Selective Metal Photo Deposition

“…4 Interest in the synthesis of colloidal semiconductorÀmetal hybrid nanostructures has grown exponentially in recent years. 1 33 Some of these reports build upon earlier work on the surface modification of microcrystalline semiconductors using platinum group metals as a way to generate hydrogen evolving photocatalysts, for example, CdSÀPt doped wth Zn and Ag sulfides, 34,35 and powders made of MS/CdS/M(M = Pt, Ir), 36…”

“…4 Interest in the synthesis of colloidal semiconductorÀmetal hybrid nanostructures has grown exponentially in recent years. 1 33 Some of these reports build upon earlier work on the surface modification of microcrystalline semiconductors using platinum group metals as a way to generate hydrogen evolving photocatalysts, for example, CdSÀPt doped wth Zn and Ag sulfides, 34,35 and powders made of MS/CdS/M(M = Pt, Ir), 36Received: May 27, 2011 Revised:June 27, 2011ABSTRACT: Reliable synthesis of semiconductorÀmetal heterostructures would increase their availability for fundamental studies and applications in catalytic, magnetic, and opto-electronic devices. Here, we demonstrate there are three main pathways for the formation of Pt and Pd nanoparticles on CdS and CdS 0.4 Se 0.6 nanorods.…”

Nanomaterials for renewable energy production and storage

“…Hydrogen evolution stopped at the absorption edge in the tail region (>600 nm), revealing that the visible-light response of the photocatalyst is due to the band-gap transition between the valence and conduction bands. 198 The photocatalytic activity for the hydrogen evolution over CdS nanorods and nanowires has also been studied. [205][206][207][208] Fig.…”