Nonaqueous synthesis of CoOx/TiO2 nanocomposites showing high photocatalytic activity of hydrogen generation

This paper describes a nonaqueous sol-gel preparation of p-n diode-type CoOx/TiO2 nanocomposites for photocatalytic hydrogen generation. Characterization results suggested that the nanocomposites consisted of highly crystalline anatase nanoparticles and Co3O4-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 2.17 mmol g(-1) h(-1). In comparison, the hydrogen evolution rates for the reference photocatalysts Degussa P25 and sodium tantalite measured under the same conditions were 20 mu mol g(-1) and 410 mu mol g(-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 CoOx/TiO2 heterojunction photocatalysts, but also the possibility to further improve the photocatalytic activity of CoOx/TiO2 through surface engineering. (c) 2013 Elsevier B.V. All rights reserved.