Size-Dependent Strong Metal-Support Interactions in Ni/Anatase TiO2 Catalysts for Selective Guaiacol Hydrodeoxygenation

Strong metal–support interactions (SMSI) are widely recognized as a powerful strategy for tuning catalytic selectivity and stability. However, a clear understanding of how controllable parameters govern SMSI strength and its impact on reaction pathways remains limited. In this work, the effect of hydrogen pretreatment temperature and Ni particle size on the SMSI behavior of Ni/TiO2-A catalysts and their catalytic performance in guaiacol hydrodeoxygenation (HDO) was systematically investigated. The results reveal a size-dependent SMSI behavior governed by the degree of metal encapsulation: small Ni particles (1–2 nm) are fully encapsulated by TiOx species, leading to suppression of aromatic ring hydrogenation, whereas larger Ni particles (~15 nm) are partially covered and retain aromatic hydrogenation activity. At 600 °C reduction, nearly complete Ni coverage suppresses aromatic hydrogenation sites, leading to selective formation of phenolic compounds. This study highlights that Ni particle size and reduction conditions jointly control SMSI strength, which in turn governs the catalyst activity and selectivity, providing guidance for rational design of SMSI catalysts.