Highly Crystalline Wurtzite CdS Prepared by a Flux Method and Application to Photocatalysis

Highly crystalline wurtzite CdS particles with exposed crystal facets and fewer sulfur defects have been successfully prepared by heat treatment of zincblende CdS in a mixed molten salt. This method does not require a vacuum or highly toxic hydrogen sulfide conditions as in conventional annealing methods or high pressure as in conventional flux methods. The obtained wurtzite CdS photocatalyst with a Pt cocatalyst shows hydrogen evolution activity under visible light, in the presence of sulfide sacrificial reagents, and its external quantum yield at 420 nm is 19.2%. The activity is ∼50-fold higher than that of the zincblende CdS precursor and about twice as high as that of wurtzite CdS prepared by vacuum annealing, both with a Pt cocatalyst.