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The composition effect of carbon supported Ni x M 1−x (M = Bi, Pd, and Au) nanomaterials toward glycerol electrooxidation (GEOR) was evaluated in alkaline media. Ni-rich catalysts with different atomic ratios (M atomic ratio ≤20%) were synthesized by the heatless coreduction method and characterized by various physicochemical and electrochemical techniques. All structures of the Ni x M 1−x /C catalysts were composed of a rich phase of Ni(OH) 2 , as evidenced by TDA-TGA and XPS. Among the different nanomaterials, the Ni 0.9 Au 0.1 /C catalyst provided the lowest onset potential (+0.12 V vs Hg/HgO) and the highest peak current density. In situ infrared spectroscopy experiments combined with electrochemical measurements exhibited the formation of formate for all catalysts, thus indicating the breakage of C− C bonds of glycerol. GEOR led to 100% selectivity for formate after 1 h electrolysis and 100% conversion of glycerol after 24 h at +1.55 V. Furthermore, when these inexpensive catalysts were tested in tandem with cathodic CO 2 electroreduction, the anodic Ni 0.9 Au 0.1 /C catalyst displayed the highest partial current density for CO and the lowest onset potential.

Pt/C and Pt 9 Bi 1 /C catalysts are synthesized by wet chemistry, characterized by physicochemical and electrochemical methods, and evaluated towards glucose and methylglucoside electrooxidation in alkaline medium. Pt 9 Bi 1 /C leads to onset potentials 150 to 350 mV lower than those of Pt/C for glucose and methyl-glucoside oxidation, respectively. From in situ infrared spectroscopy, main reaction products of glucose and methyl-glucoside oxidation are gluconate and methyl-glucuronate, respectively. Chronoamperometry are performed for 6 hours in a 25 cm 2 electrolysis cell fitted with a Pt 9 Bi 1 /C anode to oxidize 18 g L -1 glucose and methyl-glucoside at cell voltages of 0.30 V and 0.50 V, respectively, and a Pt/C cathode to produce hydrogen. Analyses of the reaction products by high performance liquid chromatography, 13 C nuclear magnetic resonance and mass spectroscopy indicate that gluconate and methyl-glucuronate are formed with 100% faradaic efficiency and 100 % selectivity at 40 % glucose and 37 % methyl-glucoside conversion, respectively.

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.

The effects of cell voltage and of concentration of sugars (glucose and xylose) on the performances of their electro-reforming have been evaluated at a Pd3Au7/C anode in 0.10 mol L−1 NaOH solution. The catalyst synthesized by a wet chemistry route is first comprehensively characterized by physicochemical and electrochemical techniques. The supported catalyst consists in alloyed Pd3Au7 nanoparticles of circa 6 nm mean diameter deposited on a Vulcan XC72 carbon support, with a metal loading close to 40 wt%. Six-hour chronoamperometry measurements are performed at 293 K in a 25 cm2 electrolysis cell for the electro-conversion of 0.10 mol L−1 and 0.50 mol L−1 glucose and xylose at cell voltages of +0.4 V, +0.6 V and +0.8 V. Reaction products are analyzed every hour by high performance liquid chromatography. The main products are gluconate and xylonate for glucose and xylose electro-reforming, respectively, but the faradaic yield, the selectivity and the formation rate of gluconate/xylonate decrease with the increase of aldose concentration, whereas lower faradaic yields and higher formation rates of gluconate/xylonate are observed at +0.8 V than at +0.4 V (higher chemical yields).

The electrooxidation of glucose on gold (Au) and platinum (Pt) nanoparticles (NPs) is investigated in alkaline medium by cyclic voltammetry after chronoamperometry at different potentials (+0.100 V, +0.200 V and +0.400 V vs the reversible hydrogen electrode, RHE), in situ Fourier transform infrared spectroscopy and differential electrochemical mass spectrometry measurements. We show that glucose can adsorb on both metallic Au and Pt surfaces at low potentials, but that the adsorbed species are different: hydrogen atoms, carbon monoxide (CO), lactones and gluconate species on Pt-NPs, and only hydrogen atoms and gluconate species on Au-NPs. On Pt-NPs, the first oxidation peak between +0.050 V vs RHE and +0.250 V vs RHE is due to glucose adsorption and hydrogen atoms oxidation into protons (H + ), whereas the second electrochemical feature between +0.250 V vs RHE and +0.800 V vs RHE is due to the oxidation of glucose into lactone, gluconate and of adsorbed CO into carbon dioxide (CO 2 ). For Au-NPs, adsorbed hydrogen atoms are not oxidized into H + but transformed into molecular hydrogen H 2 , and glucose is adsorbed as gluconate species that are desorbed into gluconates for potentials higher than +0.300 V vs RHE.

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Palladium nanoparticles (Pd-NPs) with controlled distributions of sizes and shapes (nanospheres–Pd-NS-, nanocubes -Pd-NC-, and nanooctahedrons -Pd-NO-) are synthesized by wet chemistry methods and characterized by TEM/HRTEM. The surfaces of Pd-NPs are modified by spontaneous adsorption of gold and characterized by cyclic voltammetry in acidic medium. It is shown that the modification of Pd-NPs by dipping in HAuCl 4 solutions of different concentrations allows controlling the surface coverage by gold. It is also shown that the modification of Pd-NPs surfaces involves first the formation of PdAu surface alloys. For higher coverages, both PdAu surface alloys and pure Au structures are formed. The activity toward the glucose electrooxidation reaction is determined by linear scan voltammetry (LSV). Higher activity is observed on pure Pd-NC presenting extended (100) surfaces than on Pd-NO with mainly (111) surface orientation and on Pd-NS without preferential surface orientation, both these latter Pd-NPs displaying almost the same activity. The modification of the surface by spontaneous adsorption of gold greatly improves the activity of all Pd-NPs. However, Au-modified Pd-NC materials remain the most active catalysts. PdAu surface alloys seem to be involved in the improvement of the catalytic activity at low potentials, although the role of pure gold structures on Pd-NPs toward the enhancement of the catalytic activity cannot be excluded for high gold coverage. The study allows a better understanding of the material structure/electrocatalytic behavior relationship.