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

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 L1$_{0}$ 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.