二酸化チタンの表面構造が水による阻害を制御（Surface Structure Controls Water Inhibition on Titanium Dioxide）

2026-09-29 パシフィック・ノースウェスト国立研究所（PNNL）

Water reorganizes adsorbed isopropanol into facet-specific surface complexes that alter the reaction barrier for an isopropanol dehydration reaction. (Image by Cortland Johnson | Pacific Northwest National Laboratory, courtesy of Angewandte Chemie International Edition)

＜関連情報＞

• https://www.pnnl.gov/publications/surface-structure-controls-water-inhibition-titanium-dioxide
• https://onlinelibrary.wiley.com/doi/10.1002/anie.2431054

異なる水-アルカノール錯体を介してTiO2上でのアルカノール脱水反応を阻害する、面依存的な水の影響 Facet-Dependent Water Inhibition of Alkanol Dehydration on TiO2 via Distinct Water–Alkanol Complexes

Wenda Hu, Haiting Cai, Anthony Savoy, Jinshu Tian, Sungmin Kim, Fan Lin, Junrui Li, Hao Xu, Yiqing Wu, Zihao Zhang, Nicholas Jaegers, Huamin Wang, Feng Gao, Jianzhi Hu
Angewandte Chemie International Edition  Published: 07 June 2026
DOI:https://doi.org/10.1002/anie.2431054

ABSTRACT

Water is ubiquitous in biomass-derived feeds, yet its molecular impact on oxygen-elimination reactions remains poorly understood, particularly for catalysts exposing different facets. Here, we utilize well-defined TiO₂ nanocrystals with dominant (101) and (001) facets to reveal a pronounced facet-dependent effect of water, where inhibition for dehydration of isopropanol (IPA) on the TiO₂(001) surface is about four times more severe than TiO₂(101). Through a combination of in situ solid state NMR, in situ infrared spectroscopy, kinetics studies, and theoretical calculations, we demonstrate that this disparity arises from the formation of distinct alkanol-water complex intermediates. On TiO₂(001), IPA undergoes dissociative adsorption to form an isopropoxide-H₂O complex that readily drives the surface into a complex-dominated regime. This pathway increases the activation barrier for C–H cleavage by 40 kJ mol⁻¹ by inducing a disordered transition state. In contrast, TiO₂(101) favors molecular IPA adsorption with weak hydrogen bonding to water, resulting in a smaller complex formation constant and a much smaller activation barrier increase (25 kJ mol⁻¹). By quantitatively linking facet-dependent complex coverage to transition-state destabilization, this work moves beyond simple site-blocking models and provides a conceptual framework for designing catalysts that remain active in water-containing environments.