Sathiyan Krishnamoorthy, Bar-Ziv Ronen, Marks Vered, Meyerstein Dan, Zidki Tomer
Department of Chemical Sciences, Ariel University, Centers for Radical Reactions and Material Research and the Schlesinger Family Center for Compact Accelerators, Radiation Sources and Applications, Kyriat Hamada 3, Ariel, 40700, Israel.
Department of Chemistry, Nuclear Research Center Negev, P.O. Box 9001, Beer-Sheva, 84190, Israel.
Chemistry. 2021 Nov 17;27(64):15936-15943. doi: 10.1002/chem.202103040. Epub 2021 Oct 13.
Photocatalytic hydrogen production is proposed as a sustainable energy source. Simultaneous reduction and oxidation of water is a complex multistep reaction with high overpotential. Photocatalytic processes involving semiconductors transfer electrons from the valence band to the conduction band. Sacrificial substrates that react with the photochemically formed holes in the valence band are often used to study the mechanism of H production, as they scavenge the holes and hinder charge carrier recombination (electron-hole pairs). Here, we show that the desired sacrificial agent is one forming a radical that is a fairly strong reducing agent, and whose oxidized form is not a good electron acceptor that might suppress the hydrogen evolution reaction (HER). In an acidic medium, methanol was found to fulfill both these requirements better than ethanol and propan-2-ol in the TiO -(M -NPs) (M=Au or Pt) system, whereas in an alkaline medium, the alcohols exhibit a reverse order of activity. Moreover, we report that CH (OH) is by far the most efficient sacrificial agent in a nontrivial mechanism in acidic media. Our study provides general guidelines for choosing an appropriate sacrificial substrate and helps to explain the variance in the performance of alcohol scavenger-based photocatalytic systems.
光催化制氢被认为是一种可持续能源。水的同时还原和氧化是一个具有高过电位的复杂多步反应。涉及半导体的光催化过程将电子从价带转移到导带。与价带中光化学形成的空穴发生反应的牺牲底物常被用于研究产氢机理，因为它们能清除空穴并阻碍电荷载流子复合（电子 - 空穴对）。在此，我们表明理想的牺牲剂是一种形成自由基的物质，该自由基是一种相当强的还原剂，且其氧化形式不是可能抑制析氢反应（HER）的良好电子受体。在酸性介质中，发现在TiO₂-(M - NPs)（M = Au或Pt）体系中，甲醇比乙醇和2 - 丙醇更能满足这两个要求，而在碱性介质中，醇类表现出相反的活性顺序。此外，我们报道在酸性介质中，通过一种非平凡的机理，CH₃OH是迄今为止最有效的牺牲剂。我们的研究为选择合适的牺牲底物提供了通用指导方针，并有助于解释基于醇类清除剂的光催化体系性能的差异。
