Yamada Kento, Suzuki Hajime, Abe Ryu, Saeki Akinori
Department of Applied Chemistry, Graduate School of Engineering , Osaka University , 2-1 Yamadaoka , Suita , Osaka 565-0871 , Japan.
Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering , Kyoto University , Nishikyo-ku, Kyoto 615-8510 , Japan.
J Phys Chem Lett. 2019 Apr 18;10(8):1986-1991. doi: 10.1021/acs.jpclett.9b00880. Epub 2019 Apr 9.
Strontium titanate (SrTiO) is a perovskite that is important in water-splitting photocatalytic chemistry. Although excess Sr is known to improve the photocatalytic activity, its effect on charge dynamics remain largely unaddressed. Herein, we present a detailed analyses of gigahertz complex transient photoconductivity (Δσ) measured using time-resolved microwave conductivity (TRMC). We show that charge carrier trapping associated with the emergence of an anomalous positive imaginary part and the first-order rate constant of the normal positive real part of Δσ dramatically decreased with increasing Sr/Ti ratio. The second-order rate constant attributed to charge recombination simultaneously decreased, and these rate constants were well correlated with the improved hydrogen evolution rate of aqueous SrTiO suspensions with a Pt co-catalyst. These findings provide a fresh perspective on the stoichiometry-carrier dynamics relationship paramount for the optimization of composition-engineered photocatalysts and reveal the broad implications for mechanistic studies based on TRMC evaluation.
钛酸锶（SrTiO）是一种在光催化水分解化学中具有重要意义的钙钛矿。尽管已知过量的Sr能提高光催化活性，但其对电荷动力学的影响在很大程度上仍未得到解决。在此，我们对使用时间分辨微波电导率（TRMC）测量的千兆赫兹复瞬态光电导率（Δσ）进行了详细分析。我们表明，与异常正虚部的出现相关的电荷载流子俘获以及Δσ正常正实部的一级速率常数随着Sr/Ti比率的增加而显著降低。归因于电荷复合的二级速率常数同时降低，并且这些速率常数与含铂助催化剂的SrTiO水悬浮液中析氢速率的提高密切相关。这些发现为优化成分工程光催化剂至关重要的化学计量 - 载流子动力学关系提供了新的视角，并揭示了基于TRMC评估的机理研究的广泛意义。
