Hierarchical composites of TiO2 nanowire arrays on reduced graphene oxide nanosheets with enhanced photocatalytic hydrogen evolution performance

In this study, hierarchical composites of reduced graphene oxide (RGO)-TiO2 nanowire arrays were prepared via an in situ controlled growth process and subsequent calcination. A more homogeneous mixture was formed and strong interaction between RGO nanosheets and anatase TiO2 nanowires existed, which help the interfacial charge transfer and separation. Electrochemical impedance spectroscopy (EIS), surface photovoltage spectroscopy (SPV) and transient photovoltage (TPV) were used to study the interfacial charge transfer process. The prepared hierarchical RGO-TiO2 nanowire array composites showed excellent H-2 production activity in the absence of noble metal cocatalysts, which was much higher than that of the pure anatase TiO2 and RGO-TiO2 generated by mechanical mixing. It was mainly attributed to the synergetic effect of the improved electron-hole pair separation rate, increased catalytic active sites and high light harvesting provided by the special hierarchical structure. The approach for the preparation of the hierarchical composite in this study may guide the way for designing new composite materials for enhanced photocatalytic and photoelechemical performance.