Ag Electrodeposited on Cu Open‐Cell Foams for the Selective Electroreduction of 5‐Hydroxymethylfurfural

Abstract

The electrocatalytic conversion of 5‐hydroxymethylfurfural (HMF), a biomass platform molecule, to 2,5‐bis(hydroxymethyl)furan (BHMF), a polymer precursor, is a fully sustainable route that operates at room temperature and pressure, using water as source of hydrogen, and avoids high H2 pressures. In this work, we investigate the use of 3D electrocatalysts, made by Ag0 electrodeposited on Cu open‐cell foams (Ag/Cu), to improve the efficiency in the electrochemical conversion of HMF to BHMF in basic media at different HMF concentrations. For comparison purposes, Ag and Cu bulk foams as well as Ag, Cu and Ag/Cu foil counterparts are investigated. For diluted 0.02 M HMF solutions, BHMF is selectively produced at high HMF conversion and FE over Ag/Cu foams. The large surface area of 3D Ag/Cu foams, compared to their 2D counterparts, does not affect selectivity, but increases the rate of conversion and in turn the productivity. However, it would appear that the increase in the surface area is not enough to increase the efficiency in the conversion of more concentrated HMF electrolytes (0.05–0.50 M). The productivity of Ag/Cu is modified with electrocatalytic cycles.

AgCu Bimetallic Electrocatalysts for the Reduction of Biomass-Derived Compounds

“…Note that the dimer is generated by the coupling of radicals and its formation is fostered by increasing the HMF concentration in the electrolyte. 11 Hence, the deposition of Ag over Cu foams also determines the selectivity of the reduction process. The conversion and selectivity in BHMF of the Ag/Cu ED and GD catalysts are rather similar after the accumulation of the same charge (241 C).…”

“…The deposition/dissolution charge of Pb on the foams was compared with the response of polished Ag foil. 11 Cyclic voltammetries (CVs) were recorded in a single compartment three-electrode cell between 0 and −0.6 V vs SCE (from 0.79 to 0.19 vs RHE) with a scan rate of 50 mV s –1 . The electrolyte was an aqueous solution of 0.10 M sodium potassium tartrate containing 0.01 M H 2 SO 4 and 3 × 10 –4 M Pb(NO 3 ) 2 .…”

“…In the HPLC chromatograms, an intense peak close to the one for BHMF was detected, which was related to 5,5′-bis(hydroxymethyl)hydrofuroin, in agreement with gas chromatography–mass spectrometry (GC–MS) and electrospray ionization-mass spectrometry (ESI-MS) analyses. 11 Unfortunately, we were not able to quantify the amount of the byproduct; hence, the area of the peak was used to estimate its formation during the electroreduction experiments over the different investigated electrocatalysts.…”

“…For instance, the electrochemical conversion of benzaldehyde to benzyl alcohol is a model reaction for the ambient temperature post-pyrolysis treatment of bio-oil. 5 , 6 Moreover, the electroreductions of furfural 7 , 8 and 5-hydroxymethylfurfural (HMF) 9 − 11 biomass-platform molecules produce furfuryl alcohol and 2,5-bis(hydroxymethyl)furan (BHMF), which are precursors of polymers, and 2-methylfuran and 2,5-dimethylfuran (DMF), which can be used as fuel additives.…”

“… 9 Recently, some of us reported that the combination of electrodeposited Ag nanoparticles and 3D Cu open-cell foams produces electrocatalysts with hierarchical porosity, outperforming flat electrodes. 11 Nanostructuring is an efficient way to intensify the electrocatalyst activity since it provides a greater number of active sites compared to the bulk metal, increasing the exchanged current. 18 Galvanic displacement 17 , 19 and electrodeposition 20 − 22 are two simple methods to nanostructure the surface of Cu supports with Ag particles of different morphologies.…”