Hydrogen from electrochemical reforming of C1–C3 alcohols using proton conducting membranes

Abstract

This study investigates the production of hydrogen from the electrochemical reforming of short-chain alcohols (methanol, ethanol, iso-propanol) and their mixtures. High surface gas diffusion Pt/C electrodes were interfaced to a Nafion polymeric membrane. The assembly separated the two chambers of an electrochemical reactor, which were filled with anolyte (alcohol+H2O or alcohol+H2SO4) and catholyte (H2SO4) aqueous solutions. The half-reactions, which take place upon polarization, are the alcohol electrooxidation and the hydrogen evolution reaction at the anode and cathode, respectively. A standard Ag/AgCl reference electrode was introduced for monitoring the individual anodic and cathodic overpotentials. Our results show that roughly 75% of the total potential losses are due to sluggish kinetics of the alcohol electrooxidation reaction. Anodic overpotential becomes larger as the number of C-atoms in the alcohol increases, while a slight dependence on the pH was observed upon changing the acidity of the anolyte solution. In the case of alcohol mixtures, it is the largest alcohol that dictates the overall cell performance.

Overpotential analysis of alkaline and acidic alcohol electrolysers and optimized membrane-electrode assemblies

“…Electrochemical Impedance Spectroscopy(Figure 4) was used to further characterize the electrolysers. As discussed in our previous study44 , the ohmic resistance is affected by the presence of alcohols for the case of Nafion-based cells (4.1, 6.5 and 5.0 Ω for methanol, ethanol and iso-propanol respectively) indicating that interfacial phenomena take place and lead to ohmic losses (changes in Nafion conductivity or membrane swelling). On the other hand, the ohmic losses remain unchanged for the case of doped-PBI (10.4 Ω), indicating that these interfacial phenomena are suppressed (the presence of alcohols causes less degree of swelling and/or negligible changes in the ionic conductivity of doped PBI membranes).The low-frequency semicircle at the Nyquist plot is related to the anodic reaction since it is clearly affected by the kind of alcohol and the type of polymeric membrane.…”

“…The experiments were carried out in a dual-chamber, separated electrochemical reactor made from borosilicate glass (Pine Research Instrumentation, figure S2) as described elsewhere 44 . The catholyte chamber was filled with 0.3 M H2SO4 or 0.3 M KOH solution for the experiments with H + and OHconducting membranes respectively.…”

“…electrolysis of iso-propanol shows high anodic overpotentials at both acidic and alkaline polymeric electrolytes, suggesting that iso-propanol electrolysis is not a viable technology under the tested conditions. We assume that the high anodic overpotentials obtained with iso-propanol are mainly related to the formation of strongly adsorbed intermediates [44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60] .…”

“…Comparison of the current for different values of anodic overpotential, ionic agents and kinds of alcohol.Data for Nafion are obtained from literature44 .…”

Greener Routes to Biomass Waste Valorization: Lignin Transformation Through Electrocatalysis for Renewable Chemicals and Fuels Production

“…Water electrolysis is aw ell-established method for hydrogen production.H owever,t his process still suffers from high cost due to the expensive noble-metale lectrocatalysts neededa nd the high energy demands associated with the high potential neededf or the OER. [54, 140 141] Among other organic molecules, such as methanol, [142][143][144][145] ethanol, [146][147][148][149][150][151] glycerol, [152,153] 5-HMF, [154,155] or even whole biomass, [156,157] lignin oxidation has been explored as al ower cost and lower energy alternative to water electrolysis to replaceanodic oxidation while co-generating hydrogen at lower potentials. Early studies by Ghatak et al demonstrated that BL electrolysis occurred at al ower potential [83,84] and could be optimized to produce CO 2 -free hydrogen gas with high energye fficiency.…”