Glycerol In Alkaline Medium Research Articles

Hydrothermal Transformation of Glycerol to Lactic Acid in Alkaline Medium Using Cu Catalysts Obtained from Hydrotalcite-Like Precursors

PurposeThe conversion of glycerol into lactic acid in alkaline medium using heterogeneous catalysts has been highlighted and has proved to be an efficient alternative to the conventional fermentative route. This work investigated the production of lactic acid from glycerol in alkaline medium using copper catalysts obtained from hydrotalcite-like precursors in a continuous flow reaction system and the effect of different copper loading on catalytic behaviors in terms of yield and selectivity to lactic acid.MethodsThe catalysts were synthesized by the coprecipitation method and characterized by XRF, XRD, N2 adsorption–desorption, H2-TPR, CO2-TPD, and the copper dispersion (i.e., metal atoms exposed) was determined by N2O oxidation. The reaction was performed for 30 h at 240 °C, 35 atm, using space velocity (WHSV) of 2 h−1, solution of 10 vol% glycerol, and NaOH/glycerol molar ratio of 0.75.ResultsAlthough the 30CuHT catalyst presented higher BET surface areas, Cu dispersion, and basicity than the 20CuHT catalyst, the best results in terms of glycerol conversion (96.5%) and yield (64%) to lactic acid were obtained in the catalytic test performed with the 20CuHT catalyst.ConclusionThis result may be related to the reaction steps that occur in the liquid phase in the presence of the hydroxyl group (\({\text{OH}}^{-}\) Furthermore, the high content of Cu may favor the hydrogenation of the reaction intermediates (2-hydroxypropenal and pyruvaldehyde), increasing the formation of 1,2-propanediol and consequently reducing the yield of lactic acid. The catalytic activity of the reduced and non-reduced catalysts was investigated, and the results showed that copper oxide also has catalytic activity. However, the reduction of copper oxide provides better results.Graphical Abstract

Glycerol electrooxidation on carbon-supported Pt-CuO and PtCu-CuO catalysts

Herein, Pt and Pt0.85Cu0.15 nanoparticles were deposited over hybrid CuO/C supports (1.5, 3 and 5 wt.% on carbon) by a pulsed microwave-assisted reduction method and the as-prepared materials were evaluated as electrocatalysts toward the electrooxidation of glycerol in alkaline medium. The structural and morphological analysis showed that the platinum particles decrease from 4.2 nm to around 3.0 nm in size when the CuO crystallites are present on the surface of the carbonaceous material. The electrochemical experiments indicated that the nanoparticles deposited over the hybrid support present significantly improved electrocatalytic properties compared to Pt/C. Among them, Pt0.85Cu0.15CuO(3)/C catalyst exhibited the best performance for the GOR, delivering a mass activity of around 270 mA mgPt−1 at a fixed potential of 0.7 V, which is 5.4 times higher than that of Pt/C (∼50 mA mgPt−1). The results showed that the addition of very small amounts of copper oxide on the surface of the carbonaceous support and the addition of a small amount of Cu to Pt boost the activity of the active sites via the bifunctional mechanism, geometric strain and ligand effects.

Catalytic oxidation of glycerol in alkaline medium – Influence of mass transport limitations

AbstractGlycerol upgradation via oxidation is characterized by a complex reaction network, further complicated by the heterogeneous (gas/liquid/solid) nature of the reaction. Thus, rates and selectivities could be significantly modified by transport limitations, especially in industrial reactors. In this work, we have studied the reaction on supported Pd and Au catalysts under alkaline conditions, both in the absence and presence of transport resistances, both external and internal. Reaction pathways proposed on the basis of data under kinetic control have been used to rationalize the findings. Interestingly and counterintuitively, the selectivity to C3 compounds is better under the influence of mass transfer. This behaviour is because of the nature of the reaction, which involves solution‐mediated reactions in addition to the metal‐catalyzed reactions on the catalyst surface. These findings have important implications for the scale up of this reaction and process design methodology.

Electrochemical Studies of Pd-Based Anode Catalysts in Alkaline Medium for Direct Glycerol Fuel Cells

This study investigates the most effective electrocatalyst for glycerol oxidation reaction (GOR) in alkaline medium for five synthesized electrocatalysts, Pd, PdNi, PdNiO, PdMn3O4 and PdMn3O4NiO, supported on multi-walled carbon nanotubes (MWCNTs) prepared using the polyol method. The particle size and crystalline size of the electrocatalysts were determined using HR-TEM and XRD techniques, respectively, while EDS was used to determine the elemental composition. XRD showed crystalline sizes ranging from 3.4 to 10.1 nm, while HR-TEM revealed particle sizes within the range of 3.4 and 7.2 nm. The electroactivity, electron kinetics and stability of the electrocatalysts towards glycerol in alkaline medium was evaluated using linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA), respectively, while the electroactive surface area (ECSA) of the electrocatalysts was determined using cyclic voltammetry (CV). The metal oxide-based Pd electrocatalysts PdNiO and PdMn3O4 were the most electrochemically active, while the addition of the second metal oxide to the Pd electrocatalyst PdMn3O4NiO did not show any improvement. This was associated with this electrocatalyst having the highest particle and crystalline sizes.

Highly active Ag/C nanoparticles containing ultra-low quantities of sub-surface Pt for the electrooxidation of glycerol in alkaline media

The practical application of Pt-based technologies depends on the lowering in the costs and one way to face this challenge is by reducing the amount of Pt. Herein, we decorate Ag nanoparticles with ultra-small (0.8 %) quantities of Pt and test them for the electrooxidation of glycerol. We showed that the Pt atoms of our catalyst are one order of magnitude more active (in terms of mass activity) than Pt/C commercial catalyst. By performing in situ FTIR measurements, electrolysis experiments and HPLC analysis, we showed that both catalysts form mainly glycerate and lactate, but Pt/C is more prone to poisoning and to form carbonate. We suggest that this different behavior is attributed to the high dispersion of the Pt atoms on Ag nanoparticles. The lower probability of finding neighboring Pt atoms diminishes the formation of multiple bonded intermediates, which are precursors for the formation of carbonate and some poisoning intermediates.

Electrofabrication of the Ternary NiCuFe Alloy Nanoparticles/ERGO Nanocomposite: Effective Electrooxidation of the Glucose and Glycerol in Alkaline Media

AbstractIn this work, a facile and straightforward approach was developed to fabricate a ternary NiCuFe alloy nanoparticles (ANPs) on/in the electrochemically reduced graphene oxide (ERGO) nanocomposite at the carbon‐ceramic electrode (CE); NiCuFe‐ANPs/ERGO/CE, through a two‐step electrochemical deposition method. After physicochemical characterization of the fabricated nanocomposite, it was found that the NiCuFe‐ANPs/ERGO/CE has high electrocatalytic activity towards the oxidation of glucose and glycerol in alkaline media. The obtained results showed that the NiCuFe‐ANPs/ERGO/CE has excellent electrocatalytic activity in comparison with binary alloy nanoparticles including NiCu and NiFe in the same conditions. Moreover, the achieved results also indicated that the electrocatalytic activity of the NiCuFe‐ANPs/ERGO/CE has high value in comparison with NiCuFe‐ANPs/CE (without ERGO layers on the CE). The best results for electrooxidation of glucose (Jp=163.14 mA/cm2) and glycerol (Jp=170.35 mA/cm2) were in 0.1 M KOH and 5 mM fuels concentration. Chronoamperometry and chronopotentiometry results showed that the NiCuFe‐ANPs/ERGO/CE has significant toxic tolerance and stability. Finally, to evaluate the capacity of active sites located on the surface of the NiCuFe‐ANPs/ERGO/CE, high concentrations of glucose and glycerol were used and it was found that the prepared electrocatalyst has a high capacity towards high concentrations of these fuels.

Surface Design: Exploiting the Instability of Small Nanoparticles on Metallic Substrates

Thiolated Au nanoparticles have been shown to undergo fast redistribution of the capping layer and subsequently of the metal core, when in contact with bare Au substrates. This is the result of an intricate interplay of entropic and enthalpic factors, which are likely affected by the choice of core metal and capping chemistry. This raises interesting questions, for example whether such a process could be used to modify and functionalize electrode substrates in a well-defined and controlled manner. Here, we report results for Pt and Au nanoparticles on Au and Pt substrates, based on the electrochemical response of the modified electrodes towards the oxidation of glycerol in alkaline media. Our study provides evidence that Pt nanoparticles on Au substrates remain relatively stable, while Au nanoparticles on Pt substrates readily decompose. This is in accordance with initial expectations based on the energetics of the thiol/metal bond.

Nickel-Cerium Layered Double Hydroxide as Electrocatalyst for Glycerol Oxidation

A new nickel based layered double hydroxide nanomaterial, Ni0.8Ce0.2-LDH, constituted by about 3 nm large nanoparticles exhibiting enhanced electrocatalytic properties towards oxidation of glycerol in alkaline media, was prepared by incorporation of 20 wt.% of CeIII ions into α-nickel hydroxide. This can be oxidized to CeIV, as demonstrated by X-ray photoelectron spectroscopy, a much electron withdrawing and oxidizing species responsible for electronic interactions and additional electrocatalytic active sites giving rise to synergic effects. High-resolution transmission electron microscopy images and the X-ray diffractograms indicated a material with a significantly lower size and degree of crystallinity than α-Ni(OH)2, one of the factors contributing to its enhanced electrochemical and electrocatalytic activity, as demonstrated by cyclic voltammetry and electrochemical impedance spectroscopy, suggesting a good potentiality for development of glycerol fuel cells.

Raspberry-like Pd3Pb alloy nanoparticles: superior electrocatalytic activity for ethylene glycol and glycerol oxidation.

Pd3Pb catalysts are one of the state-of-the-art catalysts for the electrooxidation of alcohols. Herein, raspberry-like Pd3Pb catalysts are synthesized via a simple method. The materials are characterized using various physical techniques. The electrocatalytic behaviors of the products towards the oxidation of ethylene glycol and glycerol are investigated. Electrochemical results show that the raspberry-like Pd3Pb nanostructure produces excellent electrocatalytic activity and stability towards the electrooxidation of ethylene glycol and glycerol in alkaline media, which endows the prepared nanostructure with promising potential in applications like fuel cells.

Cu catalysts supported on CaO/MgO for glycerol conversion to lactic acid in alkaline medium employing a continuous flow reaction system.

The production of lactic acid (LA) from glycerol in alkaline medium was investigated using Cu catalysts supported on CaO, MgO and xCaO/MgO (x = 5, 10, 15 wt%), employing a continuous flow reaction system over a period of 30 h. In addition to assessing the effect of the composition of the catalytic support, the influence of the temperature (200–260 °C), NaOH/glycerol molar ratio (0.5–1.5), hydroxide type (NaOH and KOH), as well as the influence of concentration (10 and 20 vol%) and purity of glycerol was investigated. The catalysts were prepared by a wet impregnation method and characterized by XRF, XRD, N2 adsorption–desorption, H2-TPR and CO2-TPD. The catalytic tests showed that the use of NaOH results in higher yields to LA. Cu catalysts supported on xCaO/MgO exhibited better catalytic performance than the CuCa and CuMg catalysts. The LA yield increases with the increase of the reaction temperature from 200 to 240 °C, and then decreases with a subsequent increase to 260 °C. NaOH/glycerol molar ratios greater than 1.25 are not necessary, since high yield to LA (96.9%) was obtained in the catalytic test performed using a molar ratio of 1.25. The catalysts showed excellent stability without evidence of deactivation over the evaluated period.

Bi-modified Pt Electrodes toward Glycerol Electrooxidation in Alkaline Solution: Effects on Activity and Selectivity

Herein we investigate the effect of irreversibly adsorbed bismuth on polycrystalline platinum (Ptp) on the electrooxidation of glycerol in alkaline media by combining electrochemical, spectroscopic...

NiO-promoted Pt electrocatalysts prepared by thermal decomposition of polymeric precursors for oxidation of glycerol in alkaline medium

We have investigated the electrocatalytic behavior of PtxNi(1-x)Oy/Ti electrodes during the oxidation of glycerol in alkaline medium. The catalysts were prepared by thermal decomposition of polymeric precursors, and characterized by scanning electron microscopy, energy-dispersive X-ray, and X-ray diffraction. According to cyclic voltammetry and chronoamperometry experiments, mixed catalysts with different metal compositions and high electrochemical surface area, prepared by thermal decomposition of polymeric precursors, afford higher current densities at low values of potential as compared to the PtOy/Ti electrocatalyst. In addition, the onset potential for the oxidation of glycerol shifts toward less positive values, showing that the mixed electrodes facilitate oxidation as compared to the PtOy/Ti electrocatalyst. Among the tested metal compositions, the Pt0.8Ni0.2Oy/Ti and the Pt0.9Ni0.1Oy/Ti electrocatalysts display the highest electroactivity.

Effect of Pd/C, Au/C and PdAu/C Synthesized Using Ionic Liquids in the Electro-Oxidation of Crude Glycerol in Alkaline Media

Crude glycerol as waste from the synthesis of biodiesel has been used in fuel cells to obtain electrical energy using mainly Pt-based electrocatalysts. In the present work, nanoparticles of Pd/C, Au/C and PdAu/C were synthesized and tested in the electro-oxidation reaction of crude glycerol. The synthesized materials were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), thermogravimetric analysis (TGA), high-resolution transmission electron microscopy (HR-TEM) and cyclic voltammetry. On the other hand, crude glycerol was prepared by transesterification reaction in alkaline medium and temperature with edible vegetable oil, KOH and methanol. In addition, Pd, Au and PdAu were synthesized and supported on Vulcan® carbon via green chemistry using the 2-hydroxyethylammonium formate ionic liquid. The micrographs obtained by HR-TEM revealed the presence of hemispherical particles with sizes between 8 and 30 nm. The electrocatalytic evaluation performed by cyclic voltammetry at 0.1, 0.5, 1, 1.5 and 2 M in alkaline medium of glycerol and crude glycerol. Raman spectrum of crude glycerol showed bands of methanol, soaps and glycerol, and the Raman spectrum of purified glycerol exhibited the characteristically signals of analytical glycerol. The maximum current density peak (55 mA mg-1) was obtained employing PdAu/C at 2 M glycerol. On the other hand, for 2 M crude glycerol, PdAu/C showed two maximum current densities peaks at 0.18 and 0.44 V vs NHE, associated to the oxidation of methanol and glycerol from crude glycerol. In summary, PdAu/C can be used as an alternative to Pt-based electrocatalysts for the efficient usage of crude glycerol as fuel for energy conversion applications.

Towards a fuel-flexible direct alcohol microfluidic fuel cell with flow-through porous electrodes: Assessment of methanol, ethylene glycol and glycerol fuels

A mixed media fuel-flexible direct alcohol microfluidic fuel cell (μDAFC) with flow-through configuration is introduced. The anode of the fuel-flexible μDAFC can interchangeably use methanol, ethylene glycol or glycerol in alkaline media, while saturated oxygen in acidic media feeds the cathode to generate ∼30–40 mW cm−2 of maximum power density. The performance in terms of output power density of the μDAFC is highly dependent on the fuel concentration in each case. The output power is proportional to the fuel concentration for ethylene glycol and methanol. Contrarily, glycerol shows higher power at low concentrations and vice-versa, which is rationalized as a consequence of the poisoning effect due to the limited glycerol catalysis on Pt at high concentration cases. The fuel-flexible μDAFC with consistently high power density is achieved by balancing the number of carbons participating in the ethylene glycol and methanol oxidation reactions, while glycerol must be administered in low concentrations. This concept therefore shows promise as a practical and cost-effective fuel cell solution that can operate on a range of organic, biomass-derived fuels without sacrificing power density at room temperature.

Single Step Synthesis of Porous NiCoO2 for Effective Electrooxidation of Glycerol in Alkaline Medium

Herein, we report the electrooxidation of glycerol in alkaline media in presence of highly active and durable NiCoO2 catalyst synthesized using single step solution combustion synthesis (SCS) and compare its activity with NiO and Co3O4 prepared using the same method. X-ray diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS), Scanning electron microscopy (SEM) with EDS and Transmission electron microscopy (TEM) along with EDS elemental/phase mapping were used to analyze the crystallinity, morphology and phase composition of the synthesized particles. TEM image with phase mapping confirms the existence of mixed NiCoO2 and these materials shows enhanced performance when compared with individual metal oxides. The onset potential of NiCoO2 is much lower and the oxidation current density obtained is relatively higher. More importantly, the current density and stability of NiCoO2 obtained from chronoamperometry makes it a promising catalyst for glycerol based fuel cells.

Lactic acid production from glycerol in alkaline medium using Pt-based catalysts in continuous flow reaction system

It was investigated the lactic acid (LA) production from glycerol in alkaline medium (NaOH) employing platinum (0.5 wt% PtO2) catalysts supported on Al2O3, ZnO and MgO in continuous flow reaction system over a period of 30 h. Besides the effect of catalyst supports, it was studied the influence of the temperature/pressure and NaOH/glycerol molar ratio. The catalysts were prepared by incipient wetness method and characterized by XRF, XRD, N2 adsorption–desorption, TPR, TPD-CO2 and the dispersion of platinum was determined by H2 chemisorption. The reactions were performed at 200–260 °C, 20–46 atm, with space velocity (WHSV) of 2 h−1, 10 vol% glycerol solution and NaOH/glycerol molar ratio of 0.5, 0.75 and 1.0. The results of the catalytic tests showed that the main liquid products are lactic acid and 1,2-propanediol (1,2-PDO). Using the Pt/ZnO catalyst at 240 °C/35 atm and NaOH/glycerol molar ratio = 1, it was obtained the highest lactic acid selectivity (∼80%) and yield (∼68%). However, in this reaction, the lactic acid yield decreases to around 25% if NaOH/glycerol molar ratio is reduced to 0.5. The highest yield to 1,2-propanediol (18.5%) was obtained with Pt/Al2O3 catalyst that was associated with the acidity of the catalyst. The catalysts showed excellent stability without evidence of deactivation over the evaluated period.

A comparative study for the electrocatalytic oxidation of alcohol on Pt-Au nanoparticle-supported copolymer-grafted graphene oxide composite for fuel cell application

The platinum-gold bimetallic nanoparticles supported poly(cyclotriphosphazene-co-benzidine)-grafted graphene oxide (poly(CP-co-BZ)-g-GO) composite has been prepared for electrochemical performance studies. Cyclic voltammetry and chronoamperometric studies were carried out to check the electrochemical properties of Pt-Au/poly(CP-co-BZ)-g-GO and Pt/poly(CP-co-BZ)-g-GO catalysts for methanol, ethylene glycol and glycerol in alkaline medium. The morphology and crystalline structure of the prepared Pt-Au/poly(CP-co-BZ)-g-GO and Pt/poly(CP-co-BZ)-g-GO and catalysts have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and fourier transform infrared spectroscopy (FT-IR). From the electrochemical results, it was concluded that Pt-Au/poly(CP-co-BZ)-g-GO catalyst shows higher catalytic activity and stability compared to Pt/poly(CP-co-BZ)-g-GO catalyst. The catalytic activity of Pt/poly(CP-co-BZ)-g-GO catalyst has been compared with Pt/poly(CP-co-BZ), Pt/GO and Pt/C catalysts. In addition, oxidation current of ethylene glycol is higher than the methanol and glycerol in alkaline medium on the prepared catalyst.

Preparation of a highly active palladium nanoparticle/polyoxometalate/reduced graphene oxide nanocomposite by a simple photoreduction method and its application to the electrooxidation of ethylene glycol and glycerol

A one-pot phosphotungstic-acid-assisted photoreduction approach was used to fabricate reduced graphene oxide decorated with Pd nanoparticles, with the phosphotungstic acid acting as both photocatalyst and stabilizer. The resulting nanocomposites were tested, and the electrochemical results showed that their electrocatalytic activity towards the electrooxidation of ethylene glycol and glycerol could be tailored by varying the composition of the material. As a result of the increased surface area of the reduced graphene oxide and the catalytic properties of the Pd nanomaterial and phosphotungstic acid, the prepared nanocomposite exhibited better catalytic activity towards the electrooxidation of ethylene glycol and glycerol in alkaline media than commercial Pd/C catalysts.

Electrochemical Conversion of Bio-Sourced Alcohols / Polyols and Saccharides for Platform Molecules and Hydrogen Cogeneration

The electrochemical conversion of biosourced compounds such as alcohols/polyols and saccharides gains more and more attention for their potency hydrogen and added-value-chemical cogeneration [1–4] from an energy efficient method compatible with several green chemistry principles. Alcohols and polyols can be produced from biomass (and are a by-product of biofuel industry in the case of glycerol) and represent an interesting challenge for the production of platform molecules for further chemical transformations into polymers, surfactants, etc. The main challenges are then reaching a high activity and controlling the selectivity of the anode. These challenges can be addressed by the reaction medium and the catalyst design with modification of catalytic metals (generally platinum group metal) with p-group and d-group metals to improve the activity and tune the selectivity towards desired reaction products [1,4-7]. The use of saccharide for hydrogen and value-added chemical cogeneration would represent a convenient way of introducing biosourced molecules in the hydrogen and platform molecules production chain. Indeed, a large part of cellulosic biomass which is not devoted to food industry is composed of saccharide derivatives. The production of saccharide from these resources is then less demanding in terms of energy and chemical steps than alcohol / polyol production. Furthermore, the oxidation of saccharide in alkaline medium under conditions similar to that of an electro-reforming cell [8] leads to the formation of carboxylic acids very similar to those produced from alcohol / polyol electro-reforming and to longer carboxylic acids. However, while the oxidation of saccharide such as glucose and xylose starts at low potential, it remains difficult to reach high current densities compatible with an industrial process and the reactant turnover has to be improved. Finally, the conversion of these compounds is performed with co-production of clean hydrogen on the cathode, at low cell voltage (typically less than 1 V) compared to water electrolysis [2–4,7]. Acknowledgement: The research leading to these results has received funding from the French National Research Agency (ANR) under grant agreement N° ANR-16-CE29-0007-01 (ECO-PLAN project) [1] M. Simões, S. Baranton, C. Coutanceau, Electrochemical Valorisation of Glycerol, ChemSusChem, 5 (2012) 2106–2124 [2] Y.X. Chen , A. Lavacchi, H.A. Miller, M. Bevilacqua, J. Filippi, M. Innocenti, A. Marchionni, W. Oberhauser, L. Wang, F. Vizza, Nanotechnology makes biomass electrolysis more energy efficient than water electrolysis, Nature Commun., 5 (2014) 4036 [3] C. Lamy, T. Jaubert, S. Baranton, C. Coutanceau, Clean hydrogen generation through the electrocatalytic oxidation of ethanol in a proton exchange membrane electrolysis cell (PEMEC). Effect of the nature and structure of the catalytic anode. J Power Sources, 245 (2014) 927–936 [4] C. Coutanceau, S. Baranton, Electrochemical conversion of alcohols for hydrogen production: a short overview, WIRE Energy and Environment, (2016) 388-400 [5] A. Zalineeva, A. Serov, M. Padilla, U. Martinez, K. Artyushkova, S. Baranton, C. Coutanceau, P.B. Atanassov, Self-Supported PdxBi Catalysts for the Electrooxidation of Glycerol in Alkaline Media, J. Am. Chem. Soc., 136 (2014) 3937−3945 [6] A. Zalineeva, A. Serov, M. Padilla, U. Martinez, K. Artyushkova, S. Baranton, C. Coutanceau, P.B. Atanassov, Glycerol electrooxidation on self-supported Pd1Snxnanoparticules, Appl. Catal. B: Environ., 176 (2015) 429–435 [7] J. Gonzalez-Cobos, S. Baranton, C. Coutanceau, Development of Bismuth-Modified PtPd Nanocatalysts for the Electrochemical Reforming of Polyols into Hydrogen and Value-Added Chemicals, ChemElectroChem, 3 (2016) 1694–1704 [8] A.T. Governo, L. Proença, P. Parpot, M.I.S. Lopes, I.T.E. Fonseca, Electro-oxidation of d-xylose on platinum and gold electrodes in alkaline medium, Electrochim. Acta, 49 (2004) 1535–1545

Rrde Studies of Glycerol Electro-Oxidation: Local pH Variation and Oscillatory Dynamics

Based on the fast consumption and depletion of OH- that generate considerable local pH variations from reference bulk values during anodic processes on platinum, rotating ring-disk electrode (RRDE) studies are expected to contribute in elucidating mechanisms and pH implications on kinetics. As more recently demonstrated by Feliu and co-workers[1] , significant pH variations of up to 1.5 pH units during the voltammetric electro-oxidation of ethanol in alkaline media over platinum, even under hydrodynamic conditions, were detected. Using Ptdisk-Ptring electrodes we investigated glycerol electro-oxidation in alkaline media under both conventional (Figure 1) and oscillatory conditions. All ring currents were corrected by the collection efficiency of the electrode, N, of 25.6%. Importantly, the intrinsic ohmic drop of the system might bring about distortions on the ring currents that must be taken into account in order to rule out the cross-talk of the disk and ring electrodes. Parameters such as ionic strength, distance between working and reference electrodes, and, current magnitudes in the disk require special attention in order to avoid misleading conclusions. The detection of pH variation under voltammetric conditions was done by polarizing the ring electrode at 100mV vs. RHE. The local generation of H+ is seen by the cathodic currents registered at the ring (Fig.1,bottom) whose potential is shifted to lower values due to the well-known pH dependence on the equilibrium potential (Nernstian potential). In oscillatory conditions[2] the situation is rather complicated as many soluble intermediate species are produced at the disk, introducing relevant mass-transport limitations to the oscillatory dynamics being recorded. For example, galvanostatic oxidation of glycerol is only observable in stationary conditions: rotation of the electrode modifies importantly the population of intermediates necessary to sustain oscillations. A systematic study of the effects of rotation speed and of different ring polarizations was conducted. Additionally, the interaction of platinum oxides and glycerol in alkaline media, at open circuit potential, was also followed by collection experiments with the ring polarized at different potentials. The results so far demonstrate particular features for the glycerol system unseen for other model systems, yet to be understood. Acknowledgments: A.A.Z., P.B.P. E.G.M. and H.V. acknowledge São Paulo Research Foundation (FAPESP) and Sao Paulo University Research Office for the scholarships (grants #2013-06205-3 and #2012/07313-1) and financial support (grants #2009/07629-6, #2012/21204-0, and #2013/16930-7).