Design of bimetallic Au/Cu nanoparticles in ionic liquids: Synthesis and catalytic properties in 5‐(hydroxymethyl)furfural oxidation

Abstract In alloyed nanoparticles, synergistic electronic and/or geometric effects may enhance the catalytic properties compared to their monometallic counterparts. Herein, we address the synthesis of bimetallic Au/Cu nanoparticles with different compositions by wet chemical reduction in ionic liquids. The nanoparticles were successively supported on carbon. The ionic liquid could be recycled after synthesis. Annealing of the carbon‐supported NPs at 400 °C led to NPs of the ordered intermetallic L1₀ AuCu phase. The nanoparticle‐derived catalysts were characterized by X‐ray diffraction analysis, transmission electron microscopy, X‐ray photoelectron spectroscopy and optical emission spectroscopy with inductively coupled plasma. Oxidation of biomass‐derived furans is a prominent process for biomass transformation into value‐added chemicals. Herein, the oxidation of 5‐hydroxymethyl‐2‐furfural (HMF) to 2,5‐furandicarboxylic acid (FDCA) was chosen as a model reaction to evaluate the effect of Cu addition and intermetallic structure on the catalytic performance. Particularly Au/Cu nanoparticles with an Au/Cu ratio of 3 : 1 showed very high conversion to FDCA.