Electroreforming of Glucose/Xylose Mixtures On PdAu Based Nanocatalysts

Abstract

The electroreforming of glucose/xylose mixtures has been evaluated at Pd 1-x Au x /C anodes in 0.10 mol L À 1 NaOH electrolyte. The catalysts synthesized by a wet chemistry route are comprehensively characterized by physicochemical and electrochemical techniques. From linear scan voltammetry and in situ Fourier transform infrared spectroscopy measurements, it was shown that the Pd 0.3 Au 0.7 /C material led to the best electrocatalytic behavior towards the electrooxidation of glucose/ xylose mixtures in terms of activity (higher current densities at lower potentials) and selectivity (lower dissociative adsorption). Six-hour chronoamperometry measurements were performed at 293 K in a 25 cm 2 electrolysis cell at + 0.4 V and + 0.6 V and the reaction products were analyzed by high performance liquid chromatography. The main products were gluconate and xylonate, but the contributions of xylose to all formed products was always lower in percentages than the initial xylose ratios in solutions, showing that glucose was more electro-reactive than xylose at Pd 0.3 Au 0.7 surface.

Revisited Mechanisms for Glucose Electrooxidation at Platinum and Gold Nanoparticles

“…The electrocatalytic behavior of gold could then help to integrate electrochemical methods in biorefinery by demonstrating high activity and selectivity, and lower energy cost. Indeed, electrochemical reactors often consist of divided cells separated by an ionic conductive separator allowing biomass oxidation reaction into value added compounds at the anode and either hydrogen production [7,10] or reduction reaction of biomass molecules into value added compounds (paired electrochemical processes) [37,38] at the cathode. The production of valuable compounds at both electrodes allows decreasing the total energy cost [39].…”

“…The protocol of the water-in-oil route for the synthesis of Pt-NPs/C and Au-NPs/C catalysts was described elsewhere, as well as the characterization methods to determine the metal loading, the particle and the crystallite sizes [7,10,15]. The results are given in Table 1.…”

“…Spectra were normalized considering the averaged one recorded at +0.050 V vs RHE as the reference. By this way, negative absorption bands correspond to the formation of species and positive absorption bands to the consumption of species at the electrode surface [7,10].…”

“…Non-edible lignocellulosic biomass is composed of around 20% lignin, 30-45% cellulose (linear crystalline polymers of glucose units [4]) and 20-50% hemicellulose (branched polymers of mainly xylose and glucose [5]), depending on the feedstock [4]. Therefore, hydrolysates after lignocellulosic pretreatments to separate lignin from cellulose and hemicellulose [6] contain more than 50 mol. % of glucose; glucose accounts then for more than 40 % of the whole lignocellulosic biomass (lignin accounting for ca.…”

“…20 %), which represents a very huge quantity of raw materials for production of chemicals. Noteworthy, electroreforming of glucose in an electrolysis cell can produce high value-added chemicals at the anode together with pure hydrogen at the cathode [7,8]. In this context, unveiling the oxidation mechanism of glucose (considered as a model molecule) is of paramount importance and will further allow developing active and selective catalysts in view of the production of value-added compounds, such as gluconic acid, at high conversion rate and selectivity.…”