Alteration of Hydrodeoxygenation Pathways of Ni/TiO2-A Catalyst through Controlled Regulation of Strong Metal–Support Interactions and Surface Acidity

For supported metal catalysts on reducible oxides, encapsulation of metal particles by the support due to strong metal–support interaction (SMSI) often occurs uncontrollably under hydrogen reduction and may adversely affect the catalytic performance of the catalysts. In this work, methods to finely regulate SMSI are developed and demonstrated in guaiacol hydrodeoxygenation to allow for the alteration of reaction pathways. Among alkali and alkaline earth metal ions as modifiers on the surface of Ni/anatase TiO2 (TiO2-A), Ba ions, even at very low surface coverage, are found to have the greatest effect in suppressing the cross-migration between Ni and TiO2-A induced by SMSI. The product selectivity in guaiacol hydrodeoxygenation shifts from phenolics on Ni/TiO2-A to cyclohexane/cyclohexanol on Ni–Ba/TiO2-A due to the effects of Ba ion modification on SMSI and the surface acidity of the Ni/TiO2-A catalyst. Characterizations using high-resolution transmission electron microscopy, pulsed CO adsorption, and the catalytic pathways illustrate that the exposed surface area of Ni particles is sensibly controlled by adjusting the Ba loading in a narrow range. High-angle annular dark field scanning transmission electron microscopy, in situ X-ray photoelectron spectroscopy, and theoretical calculation reveal the strong interaction between atomically dispersed Ba species and TiO2-A on the Ni–Ba/TiO2-A catalysts.