Selective Aerobic Oxidation of 5‐(Hydroxymethyl)furfural over Heterogeneous Silver‐Gold Nanoparticle Catalysts

Abstract

Bimetallic silver-gold alloy nanoparticles on zirconia with varying Ag/Au ratios were designed by a rational approach and tested as catalysts for the selective oxidation of the promising biomass platform molecule 5-(hydroxymethyl)furfural (HMF). For this purpose, colloidal Ag x Au 10-x particles with molar compositions x = 1/3/5/7/9 were prepared by laser ablation in liquids, a surfactant-free method for the preparation of highly pure nanoparticles, before adsorption on zirconia. In-depth characterization of the supported catalysts evidenced alloyed nanoparticles with distinct trends of the surface and bulk composition depending on the overall Ag/Au molar ratio as determined by X-ray photoelectron spectroscopy (XPS) and Xray absorption spectroscopy (XAS), respectively. To uncover the synergistic effect of the Ag/Au ratio, the catalysts were further studied in terms of the catalytic activity and selectivity in HMF oxidation. Either the aldehyde moiety or both functional groups of HMF were selectively oxidized depending on the Ag/Au composition resulting in 5-hydroxymethyl-2-furan-carboxylic acid (HFCA) or 2,5-furandicarboxylic acid (FDCA), respectively. Optimization of the reaction conditions allowed the quantitative production of HFCA over most catalysts, also after re-use. Only gold rich catalysts Ag 1 Au 9 /ZrO 2 and particularly Ag 3 Au 7 /ZrO 2 were highly active in FDCA synthesis. While Ag 3 Au 7 /ZrO 2 deactivated upon re-use due to sintering, no structural changes were observed for the other catalysts and all catalysts were stable against metal leaching. The present work thus provides fundamental insights into the synergistic effect of Ag and Au in alloyed nanoparticles as active and stable catalysts for the oxidation of HMF.

Laser-generated high entropy metallic glass nanoparticles as bifunctional electrocatalysts

“…With the high heating and cooling rates of more than 10 10 K/s during some particle formation processes in PLAL from the ablation plume, the NP formation is kinetically quenched [46,48,53,54]. Under these favorable conditions, the formation of amorphous oxide and carbide NPs [55][56][57][58], as well as high defect densities favorable for catalysis [57,58], have been found previously in PLAL. Due to their enhanced electrochemical properties, the synthesis of HEMG nanostructures is not only of prime relevance for applications in energy conversion and catalysis but also highly interesting from a fundamental point of view.…”

“…Hence, a direct contact between the surface atoms of the HEMG NPs and the electrolyte from carbon corrosion or directly through the nm-thick carbon shell appears to render the latter still active in OER and ORR, respectively. It is also known that, due to the extremely fast initial cooling rates associated with PLAL [54], the generated NPs can possess defect-rich surfaces and metastable phases [106] which in turn impact their electrochemical properties [58,73,107]. In addition, since the catalytic reactions occur at the particle surface, the surface compositions of the HEMG NPs must be also seriously considered, especially when the surfaces are partially occupied by different intermetallic phases.…”

Laser-Generated InOx/ZrO2 Catalysts for CO2 Hydrogenation: Role of In Situ Fragmentation and Ripening Control

“…This is supported by several publications on the optical properties of indium-based NPs , as well as Mie theory, which predicts a 5–6 times higher absorption efficiency at 532 nm than 1064 nm for elemental indium (2–13% > 0.3–2.5%), assuming a size range of 5–30 nm (and the presence of spherical particles, see Figure S1). In fact, the in situ fragmentation of larger NPs, the accompanied size reduction, and improved monodispersity were also reported when synthesizing AuAg- and PtPd-based catalysts by laser ablation. Hence, the in situ fragmentation during laser ablation appears to be an effective strategy to reduce the particle size independent of the ablated material …”

“…In fact, the in situ fragmentation of larger NPs, the accompanied size reduction, and improved monodispersity were also reported when synthesizing AuAg- and PtPd-based catalysts by laser ablation. Hence, the in situ fragmentation during laser ablation appears to be an effective strategy to reduce the particle size independent of the ablated material …”

One‐Pot Synthesis of 2,5‐Furandicarboxylic Acid from 2‐Furoic Acid by a Pd‐catalyzed Bromination–Hydroxycarbonylation Tandem Reaction in Acetate Buffer

“…In the literature, there are three main routes for the synthesis of 2,5‐FDCA as summarized in Scheme 1 . Route‐I involves oxidation of 5‐(hydroxymethyl) furfural (HMF) to 2,5‐FDCA through a number of thermal‐catalytic,[ 4 , 5 , 6 , 7 , 8 , 9 , 10 ] electrocatalytic, [11] photocatalytic [12] and biocatalytic[ 13 , 14 , 15 ] processes. Thereinto, sequential oxidation of the two functional groups (formyl and hydroxyl) bound to the furan ring leads to the formation of 2,5‐FDCA.…”