Abstract
This paper describes a nonaqueous sol-gel preparation of p-n diode-type CoO x /TiO 2 nanocomposites for photocatalytic hydrogen generation. Characterization results suggested that the nanocomposites consisted of highly crystalline anatase nanoparticles and Co 3 O 4 -like species. They showed composition-dependent activity for hydrogen production under ultraviolet light irradiation with methanol as a sacrificial agent. The nanocomposite with the optimum composition exhibited superior photocatalytic activity and a hydrogen evolution rate of 2.17mmolg -1 h -1 . In comparison, the hydrogen evolution rates for the reference photocatalysts Degussa P25 and sodium tantalite measured under the same conditions were 20μmolg -1 and 410μmolg -1 , respectively. The stability and the concentration-dependent hydrogen production with methanol or ethanol as sacrificial agent were also studied. In addition, the nanocomposite was capable of producing hydrogen, albeit in small amount, in the sacrificial agent-free conditions in the phosphate-buffered solutions. The results show not only the uniqueness of the nonaqueous synthesis for highly active CoO x /TiO 2 heterojunction photocatalysts, but also the possibility to further improve the photocatalytic activity of CoO x /TiO 2 through surface engineering. © 2013 Elsevier B.V.