Metal–Support Interaction Between Titanium Oxynitride and Pd Nanoparticles as a Tool for Tuning the Selectivity of Electrocatalytic Hydrogenation of Furfural

Electrocatalytic hydrogenation (ECH) offers a sustainable alternative to conventional hydrogenation of biomass-derived compounds by using cathodic potential instead of heat and molecular hydrogen. This study explores the ECH of furfural under acidic conditions, focusing on how metal–support interactions influence the performance of Pd-based catalysts. Two systems are compared: Pd on carbon (Pd/C) and Pd supported on titanium oxynitride-graphene oxide (Pd–TiONx/GO). Pd–TiONx/GO exhibits lower oxophilicity and a higher proton adsorption tendency than Pd/C. Additionally, its surface shows a more negative charge, indicated by a cathodic shift (≈10 mV) in the potential of zero total charge measured via N₂O reduction. These differences significantly affect catalytic behavior. While Pd/C shows roughly twice the activity for converting furfural to furfuryl alcohol (FA), Pd–TiONx/GO is over 100 times more active in producing 2-methylfuran (2-MF) and also enhances the competitive hydrogen evolution reaction. This suggests Pd–TiONx/GO has lower surface coverage by furfural and FA, allowing for more hydrogen adsorption and favouring 2-MF formation. Overall, the study demonstrates that Pd's electrosorptive and catalytic properties can be tuned via electronic effects from the TiONx support, enabling selective manipulation of ECH pathways.