Roles of cocatalysts in Pt–PdS/CdS with exceptionally high quantum efficiency for photocatalytic hydrogen production

The essentials of the exceptionally high quantum efficiency (93%) of photocatalytic hydrogen production on Pt–PdS/CdS have been investigated by studying the roles of the dual cocatalysts Pt and PdS in photocatalysis. In situ photoelectrochemical measurements, photoluminescence spectroscopy and high-resolution transmission electron microscopy characterizations indicate that the exceptionally high QE can be attributed to vital factors including PdS and Pt as the oxidation and reduction cocatalysts, respectively; the efficient utilization of the photogenerated electrons, including those at the shallow trap states of CdS, for photocatalytic reactions; and the facial charge transfer between the cocatalysts and CdS through atomic heterojunctions. Combinations of Pt with other metal sulfides and PdS with other noble metals as dual cocatalysts also show an evident synergetic effect on the activity. The co-loading of Pt and PdS on other sulfide semiconductors results in the same enhancement of photocatalytic activity. It is proposed that the crucial role of dual cocatalysts is general for photocatalysis.