Effects of crystalline phase and morphology on the visible light photocatalytic H2-production activity of CdS nanocrystals

Visible light photocatalytic H 2 -production from aqueous solutions is of great importance for its potential application in converting solar energy into chemical energy. In this study, a series of CdS nanostructures with different contents of wurtzite (WZ) and zinc blende (ZB) phases were successfully synthesized by a simple solvothermal route in an ethylenediamine and ethylene glycol mixed solution. The solvent volume ratio of ethylenediamine in the mixed solution ( R ) exhibited an obvious influence on the crystalline phase and morphology of the resulting CdS products. With increasing R , the percentage of wurtzite first increased and then decreased, whilst the morphology changed from nanoparticles to multi-armed nanorods, and finally to long rods and sheets. The prepared multi-armed CdS nanorod samples showed especially high and stable photocatalytic H 2 -production activity with Pt (0.25 wt%) as a co-catalyst and lactic acid aqueous solution as a sacrificial reagent under visible light irradiation. The optimized CdS nanorods with the highest percentage (64%) of the WZ phase exhibited a high H 2 -production rate of 231.4 μmol h −1 (about 16.6 times higher than that of CdS nanoparticles with a low percentage (38.4%) of WZ CdS) and with a quantum efficiency (QE) of 28% at 420 nm. This high photocatalytic H 2 -production activity could be attributed to the results of the positive synergistic effects of the hexagonal WZ phase and morphology of multi-armed nanorods. Optimized multi-armed CdS nanorods with a high percentage of wurtzite, prepared by a simple solvothermal route, exhibited high visible-light photocatalytic H 2 -production performance.