Atom level revelation of the synergistic effect between Pd and Au atoms in PdAu nanoalloy catalyst for aerobic oxidation of 5-hydroxymethylfurfural

[Display omitted] •Pd-Au dual single atom catalyst (SAC) and PdAu nanoalloy catalyst were synthesized.•Liquid phase aerobic oxidation of 5-hydroxymethylfurfural over Pd-Au SAC and PdAu nanoalloy were compared.•Pd-Au dual SACs had much worse catalytic activity and PdAu nanoalloy gave much higher FDCA yield.•DFT shows that highly positive charged Pd sites or Au sites in Pd or Au SACs have a low capability for O2 and intermediates adsorption.•DFT calculation suggests that Pd dimer in Au (111) were the most favorable active sites in catalyzed HMF oxidation. PdAu nanoalloy catalyst is widely used in liquid phase aerobic oxidation reactions. However, how Pd and Au atoms in PdAu nanoalloy catalyst worked synergistically and whether single atom isolated Pd or Au atoms are superior than their nanoparticle or nanoalloy counterparts in liquid phase are less investigated. Here, with nitrogen doped carbon as supporting material, Pd, Au dual single-atom-catalysts (SACs) and PdAu nanoalloy catalyst are prepared and compared in catalyzed aerobic oxidation of 5-hydroxymethylfurfural (HMF). The results show that Pd, Au dual SACs had much worse catalytic activity for the transformation of HMF into 2,5-furandicarboxylic acid (FDCA). Remarkably, PdAu nanoalloy catalyst gives excellent catalytic activity. DFT calculations demonstrate that the charge state of Pd sites can be varied obviously with the changing of surrounding coordination atoms. Pd dimer in Au (111) was shown to be the most favorable active sites. This work emphasizes the importance of coordination atoms type, number in catalyst synthesis on their catalytic activity and opens an avenue in future rational design of Pd and Au based SAC.