Daldossi Chiara, Di Valentin Cristiana, Selloni Annabella
Department of Materials Science, University of Milano-Bicocca, via R. Cozzi 55, Milano 20125, Italy.
Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States.
ACS Catal. 2025 Jun 18;15(13):11487-11501. doi: 10.1021/acscatal.5c01848. eCollection 2025 Jul 4.
The photocatalytic oxidation of formic acid (FA), which is one of the most abundant volatile organic compounds, is a promising air remediation technology inspired by nature. However, the detailed mechanism of this photocatalytic reaction on the surface of TiO, a typical photocatalyst, is not yet well-understood. In this work, we present a computational mechanistic study of the thermal vs photocatalytic oxidation of FA on dry and hydrated anatase TiO (101) surfaces, based on periodic hybrid density functional theory (DFT) calculations, in which the photo-oxidation is treated as an excited-state process in a constrained triplet spin state. We first compare the adsorption modes of FA on the anatase (101) surface in the ground and excited states, followed by identification of the corresponding reaction intermediates that lead to the formation of CO. We unveil the pivotal role of photogenerated holes localized at surface under-coordinated oxygen sites in mediating the C-H bond cleavage, thereby promoting CO formation through a highly stable intermediate and an exergonic reaction step. Further investigation of the effect of coadsorbed water molecules shows that hydrogen bonding with water stabilizes FA in a monodentate configuration. This is favored over the unreactive bidentate structure that is the most stable under dry conditions, thus providing insight into the experimentally observed increase of the reaction rate in the presence of water.
甲酸（FA）是最丰富的挥发性有机化合物之一，其光催化氧化是一种受自然启发的很有前景的空气修复技术。然而，在典型光催化剂TiO表面上这种光催化反应的详细机理尚未得到很好的理解。在这项工作中，我们基于周期性杂化密度泛函理论（DFT）计算，对干燥和水合锐钛矿TiO(101)表面上FA的热氧化与光催化氧化进行了计算机理研究，其中光氧化被视为在受限三重态自旋状态下的激发态过程。我们首先比较了FA在锐钛矿(101)表面基态和激发态下的吸附模式，然后确定了导致CO形成的相应反应中间体。我们揭示了位于表面低配位氧位点的光生空穴在介导C-H键断裂中的关键作用，从而通过一个高度稳定的中间体和一个放能反应步骤促进CO的形成。对共吸附水分子影响的进一步研究表明，与水形成的氢键以单齿构型稳定了FA。这比在干燥条件下最稳定的无反应性双齿结构更有利，从而为实验观察到的在有水存在时反应速率增加提供了见解。
