Facet-Selective Photoelectrochemical Reactions on Wurtzite CdS Photocatalysts
Haruki Nagakawa, Tetsu Tatsuma
Abstract
Some of the photocatalytic reactions take place selectively at specific crystal planes, and knowledge in this regard has attracted much attention from the viewpoint of designing advanced and sophisticated photocatalysts. Here we report some novel facet-selective photoreduction and photo-oxidation reactions for wurtzite CdS. First we deposited Pt nanoparticles onto CdS by direct photodeposition (PD method) or an indirect process via entrapment of photoexcited electrons by reduction of Cd(II) to metallic Cd, followed by its galvanic replacement with Pt (ETD method). The PD method allowed small Pt nanoparticles to be deposited selectively on the CdS(101) facets, whereas Pt nanoparticles were deposited almost uniformly on all of the facets by the ETD method. Those CdS particles with Pt nanoparticles also showed facet-selective photocorrosion reactions based on self-oxidation. CdS–Pt prepared by the PD method exhibited selective photocorrosion at the CdS(101) facets in pure water. In the case of CdS–Pt prepared by the ETD method, however, the photocorrosion occurred selectively at the CdS(001) facets in the presence of lactic acid. These facet-selective reactions would allow the wurtzite CdS to be designed for sophisticated photocatalytic systems.