Interfacial Ru/RuO_x heterostructures on carbon support regulate selectivity in lignin hydrodeoxygenation

Area of Science:

• Catalysis
• Materials Science
• Chemical Engineering

Background:

• Biomass upgrading requires efficient catalysts to overcome scaling constraints.
• Hydrodeoxygenation (HDO) of lignin is crucial for producing sustainable liquid hydrocarbons.
• Heterostructure interfaces in catalysts can steer reaction pathways.

Purpose of the Study:

• To develop a bifunctional catalyst for one-pot lignin hydrodeoxygenation.
• To investigate the formation and properties of Ru/RuOx heterostructures on carbon nanofibers (CNF).
• To elucidate the molecular mechanisms governing lignin HDO selectivity.

Main Methods:

• Thermal restructuring of hydroxyl groups on CNF to form Ru/RuOx heterostructures.
• Catalytic testing of Ru/CNF for lignin HDO.
• X-ray absorption spectroscopy (XAS) and near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) for catalyst characterization.
• Density Functional Theory (DFT) calculations to understand reaction mechanisms.

Main Results:

• Optimized 5 wt% Ru/CNF catalyst achieved 49.1% mass yield and 67.7% carbon yield in lignin HDO.
• High selectivity towards saturated cycloalkanes was observed.
• Characterization confirmed the formation of Ru/RuOx heterostructures and tunable Ru oxidation states.
• DFT revealed polarized interfacial active sites (Oδ⁻···Ruδ++···Ruδ+) facilitating H2 activation and C-O bond polarization.

Conclusions:

• Thermal restructuring of CNF effectively creates bifunctional Ru/RuOx heterostructures for lignin HDO.
• The polarized interfacial sites enable cooperative hydrogenation and deoxygenation pathways.
• This work provides design principles for engineering advanced catalysts for sustainable fuel production.