(509a) Design Rationales for an Optimal Oxide/Metal Interface Catalyst for Hydrodeoxygenation Chemistry of Biomass Derivatives

Selective C-O cleavage is the most difficult chemical transformation en route to fuel production from biomass derivatives such as furfuryl alcohol. Metal oxide-metal interfaces have recently been used to manipulate catalytic selectivity in such multistep reactions, and also hinder non-selective decarbonylation (DCO, C-C activation). Our DFT interfacial model of TiO₂/Pd core-shell catalyst in the form of rutile TiO₂ (110) nanowire over Pd (111) provides qualitative mechanistic determination of the role of interfacial active sites towards deoxygenation and decarbonylation [1]. A TiO_2-x/Pdinterface provides a much-lowered barrier towards hydrodeoxygenation (HDO) relative to supported Pd catalysts.

We have extended the supported-TiO₂ nanowire model to predict an optimal combination of oxides and metal catalyst with interfacial properties that combine hydrogenation and redox requirements of HDO. Descriptors that dictate the synergy between the oxide and metals’ functionalities for HDO at the oxide/metal interface are evaluated, including the interfacial reducibility, metal-carbon binding energy and metal’s work function. We identify a greater stabilization of the C-O activation transition state through electronic charge redistribution at the interface, facilitated by a higher metal work function. Stronger metal-carbon binding dictates the favorable hydrogenation of the resulting organic fragment. The role of these descriptors was further investigated under experimentally relevant hydrogenation reaction conditions of H₂ and hydrocarbons partial pressures. Also, electronic perturbation of the oxide-metal interface via metal oxide doping provides an additional design variable in catalyst design for increasing the selectivity towards HDO. Doping TiO₂ favored the formation of oxygen vacancy active sites and significantly altered the HDO reaction energy barriers. Such fundamental understanding of the descriptors dictating HDO can provide opportunities for strategic tuning of the structural, electronic, and chemical properties of a multicomponent interface to achieve optimal HDO activity and selectivity.

[1] S. Deo, W. Medlin, E. Nikolla, M.J. Janik, Journal of Catalysis, 377 (2019) 28-40.