title: Effects of spatial topologies and electron Fermi-level gradient on the photocatalytic efficiency of nano-particulate semiconductors.
abstract: Nanocrystalline (nc) semiconductor materials are important in photocatalysis. The nanoparticle (NP) topologies and electron Fermi-level (EF) gradient along the interconnected NPs affect the photocatalytic efficiency (η) of the nc-materials because of the charge carrier interparticle transport (IPT). However, the detailed physiochemical kinetic mechanism remains unclear. Based on the kinetic analysis and the numerical Monte-Carlo simulation of random walks, the statistical probability distributions pRec(t) and pit(t) for the recombination time and interfacial transfer (IT) time have been proposed in this study. The recombination lifetime (τRed) and IT lifetime (τIT) were calculated by averaging pRec(t) and pit(t). The characteristic time τeof the entire electron kinetics was defined using τReand τIT, and η was calculated by dividing τeby τIT. The simulation results show that the pRec(t) clearly shows the IPT of electrons. Both the kinetic factors (NP spatial topologies and boundary barrier) and the thermodynamic factor (electron EFgradient) can affect the IPT. It was observed that the increase in IPT cannot lead to a monotonous increase in η although it can prohibit recombination. Whether the IPT can increase the η is dependent on ratio of the back IPT for recombination and the forward IPT for IT. The existence of an electron EFgradient from the electron generation site to the active site can increase η by promoting the forward IPT.
authors.affiliation: State Key Laboratory of Silicate Materials for Architectures Institution: Wuhan University of Technology, Wuhan City, Hubei province 430070, P. R. China. liubaoshun@126.com.
authors.forename: Baoshun
authors.initials: B
authors.lastname: Liu
authors.forename: Rui
authors.initials: R
authors.lastname: Zhang