Photocatalytic hydrogen generation from water using a hybrid of graphene nanoplatelets and self doped TiO2–Pd

Abstract

Nanohybrids of self doped (Ti³⁺ doped or reduced TiO₂–TiO₂R) TiO₂–graphene nanoplatelets (TiO₂R–G) of different compositions are synthesized by a facile soft chemical method. A decrease of bandgap and improved visible light absorption is exhibited by TiO₂R–G. Based on current–voltage (I–V) measurements, it is concluded that the hybrid material possesses improved electron transport properties compared to TiO₂R and pure TiO₂. A detailed characterization of the composites indicated that TiO₂R exists as a dispersed phase on graphene nanoplatelets (graphene). Among different compositions of the composites, the catalyst containing 3 weight% of graphene (TiO₂R–3G) shows enhanced photocatalytic activity for hydrogen generation from water compared to both TiO₂ and TiO₂R. When Pd is used as co-catalyst in this composite, a large increase in the activity is observed. The increased efficiency of the nanocomposite is attributed to factors like: (i) improved visible light absorption promoted by G and Ti³⁺ dopant (ii) increased lifetime of the charge carriers assisted by the enhanced electron transporting properties of G (iii) increased number of active sites for hydrogen evolution provided by the Pd co-catalyst. This work highlights the role of TiO₂ based hybrid materials as efficient photocatalysts for solar energy utilization.