Pt/TiO2 催化剂在水相中加氢醛：氧空位和溶剂水的协同作用,JACS Au

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Pt/TiO2 催化剂在水相中加氢醛：氧空位和溶剂水的协同作用
JACS Au ( IF 8.5 ) Pub Date : 2022-12-28 , DOI: 10.1021/jacsau.2c00560
Wei Cao ₁ , Guang-Jie Xia ₁ , Zhen Yao ₁ , Ke-Han Zeng ₁ , Ying Qiao ₁ , Yang-Gang Wang ₁

Affiliation

用于稳定和升级生物质的醛氢化通常在水相中使用负载型金属催化剂进行。通过结合密度泛函理论计算和从头算分子动力学模拟，甲醛加氢与Pt/TiO _{2的模型反应}用明确的溶剂水分子研究催化剂。在水相中，载体和溶剂分子上的 O 空位 (Ov) 都可以向 Pt 簇提供电荷，其中 Ov 可以显着地将 Pt 簇从正向还原为负向。在甲醛加氢过程中，水分子可以通过酸/碱交换自发地质子化醛基中的 O，通过远程质子转移在金属-载体界面产生 OH*。通过比较化学计量的和还原的TiO ₂载体，发现OH*在带正电的Pt簇上的进一步氢化比化学计量的TiO _2困难. 然而，随着 Ov 在还原载体上的存在，OH* 氢化不仅可以放出能量，而且在动力学上也更容易进行，从而防止催化剂中毒。该机制表明溶剂水分子的质子转移和 Ov 更容易的 OH* 氢化可以协同促进醛氢化。这意味着，即使对于水中这种简单的氢化反应，催化机制也可能与所有金属簇、氧化物载体和溶剂水明确相关。_{考虑到可还原氧化物载体中普遍存在的 Ov 缺陷和常见的水环境，这种协同效应可能并非 Pt/TiO 2}所独有，这对于生物质转化中的负载型金属催化剂至关重要。

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Aldehyde Hydrogenation by Pt/TiO2 Catalyst in Aqueous Phase: Synergistic Effect of Oxygen Vacancy and Solvent Water

The aldehyde hydrogenation for stabilizing and upgrading biomass is typically performed in aqueous phase with supported metal catalysts. By combining density functional theory calculations and ab initio molecular dynamics simulations, the model reaction of formaldehyde hydrogenation with a Pt/TiO₂ catalyst is investigated with explicit solvent water molecules. In aqueous phase, both the O vacancy (Ov) on support and solvent molecules could donate charges to a Pt cluster, where the Ov could dominantly reduce the Pt cluster from positive to negative. During the formaldehyde hydrogenation, the water molecules could spontaneously protonate the O in the aldehyde group by acid/base exchange, generating the OH* at the metal–support interface by long-range proton transfer. By comparing the stoichiometric and reduced TiO₂ support, it is found that the further hydrogenation of OH* is hard on the positively charged Pt cluster over stoichiometric TiO₂. However, with the presence of Ov on reduced support, the OH* hydrogenation could become not only exergonic but also kinetically more facile, which prohibits the catalyst from poisoning. This mechanism suggests that both the proton transfer from solvent water molecules and the easier OH* hydrogenation from Ov could synergistically promote aldehyde hydrogenation. That means, even for such simple hydrogenation in water, the catalytic mechanism could explicitly relate to all of the metal cluster, oxide support, and solvent waters. Considering the ubiquitous Ov defects in reducible oxide supports and the common aqueous environment, this synergistic effect may not be exclusive to Pt/TiO₂, which can be crucial for supported metal catalysts in biomass conversion.

更新日期：2022-12-28

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