Search Results (5)

The production of H₂ from renewable sources represents a crucial challenge for the planet’s future to achieve net zero emissions and store renewable energy. A possible alternative to water electrolysis (WE), which requires high potential (E > 1.48 V) to trigger the oxygen evolution reaction (OER), would be alcohol electrochemical reforming (ER), which implies the oxidation of short organic molecules such as methanol or ethanol. In ER, energy must be supplied to the system, but from a thermodynamic point of view, the energy request for the methanol or ethanol oxidation reaction is much lower than that of the OER. To study this process, an in-house 50 wt.% Pt₁Ru₁/C anodic catalyst was easily synthesized according to the Pt sulphite complex route and the impregnation of a carbon support (Ketjenblack, KB) and a Ru precursor. X-ray diffraction (XRD), X-ray fluorescence (XRF) spectroscopy, and Transmission Electron Microscopy (TEM) were used to characterize the structure, composition, and morphology of the catalyst. It appears that two distinct crystallographic phases of the Pt and Ru nanoparticles were encountered after the synthesis conducted by Ru impregnation. For the electrochemical measurements, ethanol electrooxidation (2 M CH₃CH₂OH) was studied first in a half cell with a rotating disc electrode (RDE) configuration under acid conditions and then in a direct ethanol electroreforming (or electrolysis) cell, equipped with a proton exchange membrane (PEM) as the electrolyte. The output current density was 0.93 A cm⁻² at 1 V and 90 °C in 2 M ethanol. The remarkable current densities obtained in the alcohol electrolyzer at a low voltage are better than the actual state of the art for PEM ethanol ER. Full article

This study shows the results, for the first time, of an glycerol alkaline-acid electrolyzer. Such a configuration allows spontaneous operation, producing energy and hydrogen simultaneously as a result of the utilization of the neutralization and fuel chemical energy. The electroreformer—built with a 20 wt% Pd/C anode and cathode, and a Na⁺-pretreated Nafion^® 117—can simultaneously produce hydrogen and electricity in the low current density region, whereas it operates in electrolysis mode at high current densities. In the spontaneous region, the maximum power densities range from 1.23 mW cm⁻² at 30 °C to 11.9 mW cm⁻² at 90 °C, with a concomitant H₂ flux ranging from 0.0545 STP m⁻³ m⁻² h⁻¹ at 30 °C to 0.201 STP m⁻³ m⁻² h⁻¹ at 90 °C, due to the beneficial effect of the temperature on the performance. Furthermore, over a chronoamperometric test, the electroreformer shows a stable performance over 12 h. As a challenge, proton crossover from the cathode to the anode through the cation exchange Nafion^® partially reduces the pH gradient, responsible for the extra electromotive force, thus requiring a less permeable membrane. Full article

Humanity’s overreliance on fossil fuels for chemical and energy production has resulted in uncontrollable carbon emissions that have warranted widespread concern regarding global warming. To address this issue, there is a growing body of research on renewable resources such as biomass, of which cellulose is the most abundant type. In particular, the electrochemical reforming of biomass is especially promising, as it allows greater control over valorization processes and requires milder conditions. Driven by renewable electricity, electroreforming of biomass can be green and sustainable. Moreover, green hydrogen generation can be coupled to anodic biomass electroforming, which has attracted ever-increasing attention. The following review is a summary of recent developments related to electroreforming cellulose and its derivatives (glucose, hydroxymethylfurfural, levulinic acid). The electroreforming of biomass can be achieved on the anode of an electrochemical cell through electrooxidation, as well as on the cathode through electroreduction. Recent advances in the anodic electroreforming of cellulose and cellulose-derived glucose and 5-hydrooxylmethoylfurural (5-HMF) are first summarized. Then, the key achievements in the cathodic electroreforming of cellulose and cellulose-derived 5-HMF and levulinic acid are discussed. Afterward, the emerging research focusing on coupling hydrogen evolution with anodic biomass reforming for the cogeneration of green hydrogen fuel and value-added chemicals is reviewed. The final chapter of this paper provides our perspective on the challenges and future research directions of biomass electroreforming. Full article

The electrooxidation kinetics of ethanol is key to making direct ethanol fuel cells and electrocatalytically reforming ethanol viable technologies for a more sustainable energy conversion. In this study, the electrooxidation of ethanol was investigated on nickel hydroxide (Ni(OH)₂) catalysts synthesized using a facile solvothermal method. Variations in the temperature, heating time, and the addition of oleylamine in the precursor enabled the phase and morphology control of the catalysts. X-ray diffraction and scanning electron microscopy show that the addition of oleylamine in the precursor resulted in microspheres with a high surface area, but favored the formation of β-phase Ni(OH)₂. Elevated temperatures or prolonged periods of heating in a controlled environment, on the other hand, can lead to the formation of the ethanol oxidation reaction-active α-phase. Among the synthesized catalysts, the α-Ni(OH)₂ microspheres with nanoflakes achieved the highest activity for ethanol oxidation with a current density of 24.4 mA cm⁻² at 1.55 V (vs. RHE, reversible hydrogen electrode) in cyclic voltammetry tests and stable at 40 mA cm⁻² in chronoamperometric tests at the same potential, comparatively higher than other Ni-based catalysts found in the literature. While the overpotential is beyond the useful range for direct ethanol fuel cells, it may be useful for understanding the mechanism of ethanol oxidation reactions on transition metal hydroxides at their oxidizing potential for ethanol electroreforming. Full article

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). Full article