Metal-chalcogenide nanomaterials, as compared to their wide bandgap counterparts, are particularly attractive photoelectrocatalytic materials for the conversion of solar energy into chemical energy under visible-light irradiation. In this study, the thin layer of CdTe was deposited on the surface of Au/ITO electrode using electrochemical atomic layer deposition. Deposition process was performed through the alternate under potential deposition of the Te and Cd elements with a monolayer at a time, respectively. The images of scaning electron microscopy (SEM) indicated that nanoparticles of CdTe well dispersed on Au/ITO with an average particle size about 15 nm. The results of energy dispersive analysis by X-rays (EDAX) confirmed the off-stoichiometric CdTe layer, which lead to Cd-rich CdTe because of tellurium vacancies in the deposition potential. The resulting Cd-rich CdTe/Au/ITO electrode was used for preparation of Pt/CdTe/Au/ITO by redox replacement reaction between Pt2þ and Cd excess in CdTe layer to form 1.76 wt% of Pt element which uniformly distributed on the surface of CdTe/Au/ITO. Chronoamperometric tests in sodium sulfide solution exhibited that the Cd-rich CdTe layer had n-type semiconductivity whereas the Pt/CdTe layer showed p-type semiconductivity. The Pt/CdTe/Au/ITO electrode showed higher photoelectrocatalytic activity for the HER as compared to a commercial Pt/C on Au/ITO. The onset potential for HER is almost similar and the overpotential at 10 mAcm2 is 160mV more positive on Pt/CdTe/Au/ITO under light illumination with respect to Pt/C/Au/ITO. The long-term stability tests under illumination in acidic solution revealed that Cd-rich CdTe and Pt/CdTe layeres have extremely high stablity for HER compared to Pt/C. The higher photocatalytic activity on Pt/CdTe/Au/ ITO electrode for HER is attributed predominantly to the synergistic effect of Pt, which not only serves as co-catalysts for promoting electron transfer to the electrocatalyst-electrolyte interface, but also accelerates the HER.
