Photocatalytic performance of Pd decorated TiO2–CdO composite: Role of in situ formed CdS in the photocatalytic activity

Abstract We report an enhanced photocatalytic activity for TiO 2 –CdO composite for hydrogen generation from aqueous solution of Na 2 S + Na 2 SO 3 compared to pure CdO and TiO 2 . An in situ conversion of CdO to CdS is observed during the photocatalytic reaction resulting in the formation of a CdO–CdS–TiO 2 ternary composite, which play a role in the enhanced activity. Presence of Pd as a co-catalyst in the composite increases the hydrogen production nearly ten times. As prepared composite exists as anatase phase of TiO 2 and cubic phase of CdO. Characterization of the catalyst by powder XRD, SEM and TEM suggest that a nanosized TiO 2 exists as a dispersed phase on aggregated CdO. UV-visible absorption spectrum of the composite shows features of both CdO and TiO 2 . Composite sample exhibits increased photocurrent response and has increased fluorescence lifetime for the charge carriers compared to pure CdO and TiO 2 . A detailed characterization of the used catalysts clearly shows the formation of CdS phase besides TiO 2 and CdO. This is the first report on the photocatalytic activity of TiO 2 –CdO system for hydrogen generation from water due to in situ bulk formation of CdS during the photocatalytic reaction. The in situ formed CdS in the composite enhances the photocatalytic activity in two ways: (i) CdS, whose conduction band is at higher negative potential than CdO and TiO 2 , can reduce H + more efficiently and (ii) efficient separation of photogenerated charges can occur in this composite system, resulting in increased lifetime for the charge carriers.