Graphene oxide embedded into TiO₂ nanofiber: Effective hybrid photocatalyst for solar conversion
By il Kim, Hyoung; Kim, Soonhyun; Kang, Jin-Kyu & Choi, Wonyong
Published in Journal of Catalysis
2014
Abstract
One-dimensional TiO₂ nanofibers (NFs) in which graphene oxide (GO) sheets were incorporated (GO–TiO₂ NFs) were prepared by using a sol–gel method and an electro-spinning technique. Unlike typical graphene/TiO₂ composites that have TiO₂ nanoparticles loaded on graphene/GO sheets, GO in GO–TiO₂ NF is embedded within the matrix of TiO₂ NF that consists of closely packed TiO₂ nanoparticles. GO–TiO₂ NF was characterized by various analytical methods and tested for its photocatalytic and photoelectrochemical activities. The inclusion of GO sheets in TiO₂ NF improved the photocatalytic and photoelectrochemical activities: the photocatalytic hydrogen production and photocurrent generation increased by 1.7 and 8.5 times, respectively. GO sheets embedded in TiO₂ NFs can improve the interparticle connection and facilitate the charge pair separation by serving as an in-built electron collector and conduit. Therefore, the enhanced photo(electro)chemical activities in the presence of embedded GOs are related to the retarded charge recombination rate and the lower charge transfer resistance. The advantages of GO–TiO₂ NF were confirmed by comparing with a different composite of GO/TiO₂ NF having GO sheets bound to the external surface of TiO₂ NF (GO(s)–TiO₂ NF). The photocatalytic hydrogen production with GO–TiO₂ NF was higher than GO(s)–TiO₂ NF both in the absence and presence of Pt cocatalyst, which is mainly ascribed to the stronger electronic coupling between GO sheets and TiO₂ matrix and the reduced light shielding by GO buried inside of TiO₂ NF. Whether GO sheets are present within the NF matrix or on the external surface of NF critically influences the photocatalytic activity.