Toward Facet Engineering of CdS Nanocrystals and Their Shape-Dependent Photocatalytic Activities

Controlling the shape or morphology of semiconductor nanocrystals is central to their enhanced physical and chemical properties. Herein, using CdS as a model photo catalyst, we demonstrate that the crystal habit of a visible-light-active semiconductor can be quantitatively controlled through synthesis kinetics. Growth rate control of {0001} facets (r(1)) and {10 (1) over bar1} facets (r(1')) of CdS nanocrystals was achieved by simply employing a syringe pump, which enables us to finely tune the crystal shape from nanocones, to nanofrustums, and further to nanoplates. These shape-controlled samples, showing altered proportions of {0001} to {10 (1) over bar1} facets, were used to investigate the crystal-facet dependence of solar hydrogen production. The results indicate that CdS nanoplates with the largest {0001} facets showed the highest photocatalytic activity. This work not only advances our knowledge on the growth mechanism of semiconductor crystals but also illustrates a robust method to targeted crystal design of semiconductors toward optimizing their associated catalytic activities.