Electrocatalytic oxidation of HMF to FDCA was achieved on Pd/C, Au/C and Pd–Au/C catalysts and the synergistic effect of Pd–Au alloying is clearly demonstrated with electrochemical methods.

Herein, we report an effective approach to electricity storage in biofuels by selective electrocatalytic reduction of levulinic acid (LA) to high-energy-density valeric acid (VA) or γ-valerolactone (gVL) on a non-precious Pb electrode in a single-polymer electrolyte membrane electrocatalytic (flow) cell reactor with a very high yield of VA (>90 %), a high Faradaic efficiency (>86 %), promising electricity storage efficiency (70.8 %), and a low electricity consumption (1.5 kWhL(VA)(-1) ). The applied potential and electrolyte pH can be used to accurately control the reduction products: lower overpotentials favor the production of gVL, whereas higher overpotentials facilitate the formation of VA. A selectivity of 95 % to VA in acidic electrolyte (pH 0) and 100 % selectivity to gVL in neutral electrolyte (pH 7.5) are obtained. The effect of the molecular structure on the electrocatalytic reduction of ketone and aldehyde groups of biomass compounds was investigated. Whereas LA can be fully electroreduced to VA though a four-electron transfer, the C-O groups are only electroreduced to -OH by a two-electron-transfer process when glyoxylic acid and pyruvic acid serve as feedstocks.

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2 3 1.PdAg/CNT with 2.7 nm average particle size is prepared without using surfactants. 2.Ag outperforms Pt, Pd, and Au towards electrocatalytic aldehyde oxidation. 3.PdAg/CNT has high activity towards electrocatalytic alcohol oxidation. 4.PdAg/CNT was used as a highly active anode catalyst for direct alcohol fuel cells. 5.PdAg/CNT cleaves C-C bond of glycerol more effectively than Pd/CNT. 4 ABSTRACTSPdAg supported on carbon nanotubes (PdAg/CNT) with an average particle size of 2.7 nm is prepared by an aqueous phase reduction method for alcohol oxidation reaction in direct alcohol fuel cells. In a half-cell system with three electrodes, the peak mass activity of PdAg/CNT reaches 0.105 mA µg Pd -1 , 0.305 mA µg Pd -1 , 2.105 mA µg Pd -1 , and 8.53 mA µg Pd -1 for methanol oxidation reaction, ethanol oxidation reaction, ethylene glycol oxidation reaction, and glycerol oxidation reaction, respectively, in 1 M KOH 0.1 M alcohol electrolyte. These values are higher than the mass activity of Pd/CNT at the same applied potential. With PdAg/CNT (0.5 mg Pd per MEA -1 ) as an anode catalyst, a direct methanol fuel cell, a direct ethanol fuel cell, a direct ethylene glycol fuel cell and a direct glycerol fuel cell achieve peak power densities of 135.1 mW cm -2 , 202.3 mW cm -2 , 245.2 mW cm -2 , and 276.2 mW cm -2 , with corresponding peak mass activities of 270.2 mW mg Pd per MEA -1 , 404.6 mW mg Pd per MEA -1 , 490.4 mW mg Pd per MEA -1 , and 552.4 mW mg Pd per MEA -1 , respectively, at 80 °C and ambient pressure. Ag has shown excellent activity towards aldehyde (formaldehyde, acetaldehyde, and glyoxylate) oxidation, thus, the enhancement in alcohol oxidation on PdAg/CNT is proposed due to Ag's promotion of intermediate aldehyde oxidation. PdAg/CNT also improves the fuel efficiency of glycerol oxidation by contributing to the C-C bond cleavage of C 3 glycerol to C 2 oxalate.5