DFT investigation of hydrodeoxygenation of guaiacol on Fe-decorated Ni (111)

Developing a deep understanding of the hydrodeoxygenation (HDO) processes of lignin-derived compounds is crucial for the rational design of high-performance catalysts aimed at bio-oil upgrading. In this study, we present an in-depth theoretical investigation of the HDO of guaiacol, a phenolic compound emerging from lignin, on both Ni (111) and Fe-decorated Ni (111) catalysts, utilizing density functional theory calculations. Our investigations disclose that the introduction of Fe to the Ni (111) surface enhances the adsorption stability of guaiacol. Energy barrier calculations for the initial elementary reactions of guaiacol and its HDO derivative, catechol, indicate that the most favorable reaction involves the demethylation of guaiacol and dehydroxylation of catechol on Ni (111). Fe doping does not alter the primary pathway of guaiacol and catechol HDO, yet it influences the catalysts' activity and selectivity. The rate-limiting step in converting guaiacol to catechol is the hydrogenation of R(O)(OH)∙, whereas the dehydroxylation reaction is the rate-controlling step in the conversion of catechol to phenol. It is worth noting that on Ni-based catalysts, the conversion of catechol to phenol is a slower process than the production of catechol. Additionally, the integration of Fe boosts the surface electronic activity of the Ni (111) catalyst and establishes a favorable d-band center, thereby facilitating the HDO of guaiacol.