Liu Baoshun, Zhang Rui
State Key Laboratory of Silicate Materials for Architectures Institution: Wuhan University of Technology, Wuhan City, Hubei province 430070, P. R. China.
Phys Chem Chem Phys. 2017 Apr 12;19(15):10116-10124. doi: 10.1039/c7cp00574a.
Nanocrystalline (nc) semiconductor materials are important in photocatalysis. The nanoparticle (NP) topologies and electron Fermi-level (E) 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 p(t) and p(t) for the recombination time and interfacial transfer (IT) time have been proposed in this study. The recombination lifetime (τ) and IT lifetime (τ) were calculated by averaging p(t) and p(t). The characteristic time τ of the entire electron kinetics was defined using τ and τ, and η was calculated by dividing τ by τ. The simulation results show that the p(t) clearly shows the IPT of electrons. Both the kinetic factors (NP spatial topologies and boundary barrier) and the thermodynamic factor (electron E gradient) 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 E gradient from the electron generation site to the active site can increase η by promoting the forward IPT.
纳米晶（nc）半导体材料在光催化中很重要。由于载流子的粒子间传输（IPT），纳米粒子（NP）的拓扑结构以及沿相互连接的NP的电子费米能级（E）梯度会影响nc材料的光催化效率（η）。然而，详细的物理化学动力学机制仍不清楚。基于动力学分析和随机游走的数值蒙特卡洛模拟，本研究提出了复合时间和界面转移（IT）时间的统计概率分布p(t)和p(t)。通过对p(t)和p(t)求平均来计算复合寿命（τ）和IT寿命（τ）。利用τ和τ定义了整个电子动力学的特征时间τ，并通过τ除以τ来计算η。模拟结果表明，p(t)清楚地显示了电子的IPT。动力学因素（NP空间拓扑结构和边界势垒）和热力学因素（电子E梯度）都可以影响IPT。据观察，IPT的增加虽然可以抑制复合，但并不能导致η单调增加。IPT能否提高η取决于用于复合的反向IPT与用于IT的正向IPT的比值。从电子产生位点到活性位点的电子E梯度的存在可以通过促进正向IPT来提高η。
