Visible light harvesting Pt/CdS/Co-doped ZnO nanorods molecular device for hydrogen generation

Abstract

Co-doped ZnO nanorods (Co–ZnO NRs) were synthesized by hydrothermal method using cationic surfactant cetyltrimethylammonium bromide (CTAB). Their physical growth mechanism was traced in the light of FESEM and HRTEM studies. A strong correlation between their electronic structural arrangement and photocatalytic activity was established. Broad and uniform peaks were found between 525 and 700 nm in UV–Vis. diffuse reflectance spectra, which were attributed to the d–d transition of Co2+ ion. Successful loading of the nano-sized sensitizer CdS onto the Co–ZnO NRs' surface, contributes to the band gap reduction in CdS/Co–ZnO NRs (Eg = 2.25 eV) sample. X-ray absorption spectroscopy confirms the presence of the lower degree structural disorders in CdS/Co–ZnO NRs with respect to the pristine ZnO and Co–ZnO NRs. Gradual modification in pristine ZnO NRs enhances the photocatalytic activity. Hetero-assembly of 1.5% Pt/CdS/Co–ZnO NRs, exhibited excellent photocatalytic responses in terms of quantum efficiency (1.98%) and hydrogen generation capacity (67.20 mmol/H2 g) under 1 Sun (1.5AM G) light exposure.