Electrochemical Oxidation Of Glycerol Research Articles

Electrochemical oxidation of glycerol to hydroxypyruvic acid on cobalt (oxy)hydroxide by high-valent cobalt redox centers

Transforming glycerol to value-added chemicals by mild electrochemical oxidation on earth-abundant, low-cost transition metal electrocatalysts is both environmentally and economically beneficial. Herein, substoichiometric cobalt (oxy)hydroxide CoOxHy has been demonstrated as an effective electrocatalyst for selective glycerol oxidation to hydroxypyruvic acid (HPA), an important chemical intermediate with three carbon atoms bearing three different functional groups. The Faradaic efficiency for HPA production can reach 43.2%, with an average production rate of 679.2 µmol min−1 mgeo−2. Through systematic investigation using cyclic voltammetry, step potential electrochemical spectroscopy, and in situ Raman spectroscopy characterizations, we have revealed that the high-valent cobalt center is responsible for the enhanced activity and selectivity, where electrochemically more stable CoOx exhibits much lower activity and Faradaic efficiency in comparison. This redox-mediated glycerol oxidation mechanism offers a new perspective for future electrocatalyst development toward selective glycerol valorizations.

Electrochemical Oxidation of Glycerol to Dihydroxyacetone in Borate Buffer: Enhancing Activity and Selectivity by Borate–Polyol Coordination Chemistry

Electrochemical Oxidation of Glycerol to Dihydroxyacetone in Borate Buffer: Enhancing Activity and Selectivity by Borate–Polyol Coordination Chemistry

Direct and Indirect Electrooxidation of Glycerol to Value-Added Products.

In this work, different approaches for the direct and indirect electrooxidation of glycerol, a by‐product of oleochemistry and biodiesel production, for the synthesis of value‐added products and of intermediates for biofuel/electrofuel production, were investigated and compared. For the direct electrooxidation, metallic catalysts were used, whose surfaces were modified by promoters or second catalysts. Bi‐modified Pt electrodes (Pt x Bi y /C) served as model systems for promoter‐supported electrocatalysis, whereas IrO2‐modified RuO2 electrodes were studied as catalyst combinations, which were compared under acidic conditions with the respective monometallic catalysts (Pt/C, RuO2/Ti, IrO2/Ti). Furthermore, inorganic halide mediators (chloride, bromide, iodide) and organic nitroxyl mediators (4‐oxo‐2,2,6,6‐tetramethyl‐piperidin‐1‐oxyl and 4‐acetamido‐2,2,6,6‐tetramethyl‐piperidin‐1‐oxyl) were evaluated for indirect electrooxidation. These different approaches were discussed regarding selectivity, conversion, and coulombic efficiency of the electrochemical glycerol oxidation.

Enhanced catalytic performance and changed reaction chemistry for electrochemical glycerol oxidation by atomic-layer-deposited Pt-nanoparticle catalysts

Atomically controlled thin TiO2 layers were coated onto a carbon-supported Pt nanoparticle (Pt/C) surface using an atomic layer deposition (ALD) technique. Then, the resulting TiO2 coated Pt/C (ALD(TiO2)-Pt/C) was heat-treated at 150 °C under N2 atmosphere. The heat-treated ALD(TiO2)-Pt/C (ALD(TiO2)-Pt/C(150 H T)) catalyst demonstrated improved electrocatalytic glycerol oxidation reaction (GOR) activity with a turnover frequency (TOF) 3-times higher than for uncoated Pt/C catalyst. Interestingly, the ALD(TiO2)-Pt/C(150 H T) catalyst maintained its catalytic GOR performance after a cyclic voltammetry (CV) stability test of 1200 cycles, preventing Pt sintering due to strong Pt-TiO2 interaction. The reaction chemistry for GOR on the ALD(TiO2)-Pt/C(150 H T) catalyst also changed due to the newly created Pt-TiO2 interfaces, producing more oxidized chemicals such as glyceric acid and glycolic acid. The enhanced GOR performance is related to the formation of new Pt-O-Ti bonds and to change in the physicochemical properties of the Pt by interaction between the Pt nanoparticles and ALD-coated TiO2.

Boosting the electrocatalytic glycerol oxidation performance with highly-dispersed Pt nanoclusters loaded on 3D graphene-like microporous carbon

Preparing Pt nanostructure catalysts with better support materials is an efficient catalyst design strategy to develop high performance Pt-based electrocatalysts. Here we report for the first time a method to synthesize highly-dispersed Pt nanoclusters supported on microporous three-dimensional (3D) graphene-like carbon (3D-GLC) for use in the electrochemical oxidation reaction. The Pt nanoclusters loaded on 3D graphene-like carbon (Pt/3D-GLC) are synthesized by Ca2+-exchanged beta zeolite template based carbon synthesis and subsequent Pt impregnation methods. Highly-dispersed Pt nanoclusters (ca. 1.25 ± 0.30 nm) loaded on the 3D-GLC having a large surface area (ca. 2910 m2/g) demonstrate superior electrocatalytic performance for electrochemical glycerol oxidation reaction (GOR) over that of a commercial Pt/C catalyst. We hypothesize in this work that the improved GOR performance of Pt/3D-GLC is related to the increase of Pt active sites by decreasing Pt cluster size and the change in the physicochemical properties of the Pt by interaction between the Pt cluster and 3D-GLC. In addition, first-principle density functional theory (DFT) and ab-initio molecular dynamics (MD) simulations are performed to demonstrate that the finely-dispersed Pt nanoclusters on 3D-GLC support can give rise to excellent GOR activity in accordance with the enhanced adsorption behavior of glycerol on its Pt crystal surfaces.

Development of an electrochemical biosensor for the determination of triglycerides in serum samples based on a lipase/magnetite-chitosan/copper oxide nanoparticles/multiwalled carbon nanotubes/pectin composite

A very sensitive electrochemical biosensor to determine totals triglycerides (TGs) in serum samples has been developed. It is based on the electrochemical oxidation of glycerol at glassy carbon electrodes modified with magnetic nanoparticles bonded to lipase enzyme and copper oxide nanoparticles, both supported on a multiwalled carbon nanotubes/pectin dispersion. Glycerol is produced by enzymatic reaction between the TGs present in samples and the lipase immobilized. The quantification of triglycerides was performed by amperometric measurements. The proposed electrochemical biosensor improves the performance of others methods developed for the TGs quantification. The determination of TGs does not need a pretreatment of serum samples. The PLS-1 algorithm was used for the quantification of TGs. According to this algorithm, the of detection and quantification limits were from 3.2 × 10−3 g L−1 to 3.6 × 10−3 g L−1, and from 9.6 × 10−3 to 1.1 × 10−2 g L−1, respectively. The sensitivity was 1.64 × 10−6 A L g−1. The proposed electrochemical biosensor exhibited a very good performance, a stability of 20 days, very good reproducibility and repeatability, and it is presented as a very good alternative for the determination of TGs in human serum clinical samples.

Spectroelectrochemical studies on the effect of cations in the alkaline glycerol oxidation reaction over carbon nanotube-supported Pd nanoparticles.

The effects of the alkali cations Na+ and K+ were investigated in the alkaline electrochemical oxidation of glycerol over Pd nanoparticles (NPs) deposited on functionalized carbon nanotubes (CNTs). The electrocatalytic activity was assessed by cyclic voltammetry revealing a lower overpotential of glycerol oxidation for nitrogen-functionalized Pd/NCNTs compared with oxygen-functionalized Pd/OCNTs. Whereas significantly lower current densities were observed for Pd/OCNT in NaOH than in KOH in agreement with stronger non-covalent interactions on the Pd surface, Pd/NCNT achieved an approximately three-times higher current density in NaOH than in KOH. In situ electrochemistry/IR spectroscopy was applied to unravel the product distribution as a function of the applied potential in NaOH and KOH. The IR spectra exhibited strongly changing band patterns upon varying the potential between 0.77 and 1.17 V vs RHE: at low potentials oxidized C3 species such as mesoxalate and tartronate were formed predominantly, and with increasing potentials C2 and C1 species originating from C–C bond cleavage were identified. The tendency to produce carbonate was found to be less pronounced in KOH. The less favored formation of highly oxidized C3 species and of carbonate is deduced to be the origin of the lower current densities in the cyclic voltammograms (CVs) for Pd/NCNT in KOH. The enhanced current densities in NaOH are rationalized by the presence of Na+ ions bound to the basic nitrogen species in the NCNT support. Adsorbed Na+ ions can form complexes with the organic molecules, presumably enhanced by the chelate effect. In this way, the organic molecules are assumed to be bound more tightly to the NCNT support in close proximity to the Pd NPs facilitating their oxidation.

A Hybrid Multi-Catalyst Motif for Enhanced Electro-Oxidation of Glycerol

Enzyme-based catalytic systems are common bioelectrocatalysts employed in biofuel cells, as a consequence of the inherently high volumetric catalytic activity towards oxidation of biofuels. Integration of these bioelectrocatalysts with organic oxidation catalysts extends their utility by enabling significant amplification of the electrocatalytic activity, which increases the rate of electrocatalytic oxidation of readily available biofuels. However, immobilization of organocatalysts is necessary for their use in biofuel cell applications. Herein, we describe the development of a hybrid catalytic architecture consisting of MWCNTs, TEMPO-modified linear poly(ethylenimine) (TEMPO-LPEI), and an enzyme, oxalate decarboxylase (OxDC) (MWCNT/TEMPO-LPEI/OxDC) to illustrate a synergistic enhancement in the electrochemical oxidation of glycerol. Specifically, we demonstrate that immobilized MWCNT/TEMPO-LPEI/OxDc permits enhanced electrocatalytic oxidation of glycerol by allowing the organic redox polymer, TEMPO-LPEI, to catalyze the oxidation of glycerol to mesoxalate, followed by cleavage of CO2 from mesoxalate by catalytically active MWCNTs - a crucial step in the complete oxidation of glycerol. Finally, conversion of oxalate to formate by OxDc, and subsequent oxidation of formate by TEMPO-LPEI generates CO2 while collecting up to 14 electrons per molecule of glycerol. This results in a synergistic enhancement of up to 3.3-fold. This study illustrates the promising potential of surface-immobilized, polymer hydrogel-based hybrid multicatalytic systems, and thus offers a simple methodology for fabricating bioanodes for enzymatic fuel cells.

Oxidation of Glycerol with Unactivated Electroless CuNiMoP Catalyst

Unannealed CuNiMoP electrocatalyst was found active in electrochemical oxidation of glycerol, providing over 60% conversion without optimization. Prompted by this result, the same catalyst was investigated for the thermochemical oxidation of glycerol. For the thermochemical oxidation of glycerol using the as-deposited electroless CuNiMoP catalyst, a 23 full factorial design of experiments (two level factorial experiment design with three factors) to assess the influence of temperature (A), reaction time (B) and pressure (C). The major reaction products detected by high performance liquid chromatography (HPLC) were glyceric, hydroxypyruvic, tartronic, oxalic and formic acids. The factors found to be most significant for the production of glyceric and tartronic acids were A, B, C, AB and BC. The highest percent conversion obtained for 30-min and 60-min catalysts was 10.6% and 9.4%, respectively. The presence of lactic acid was observed only for the 60-min as-deposited electroless CuNiMoP/Al2O3 catalyst. The results suggest the feasibility of an inexpensive catalyst based on non-noble metals for the thermochemical oxidation of glycerol through the electroless deposition technique. Some differences exist between the thermochemical and electrochemical product selectivity of the CuNiMoP catalyst, and reasons are suggested for the observed differences.

Effect of atomic-layer-deposited TiO2 on carbon-supported Ni catalysts for electrocatalytic glycerol oxidation in alkaline media

Thin TiO2 layers were deposited onto a carbon-supported Ni catalyst (Ni/C) through atomic layer deposition (ALD) and the resulting TiO2-coated Ni/C (ALD(TiO2)-Ni/C) was utilized for electrochemical glycerol oxidation in alkaline media. X-ray photoelectron spectroscopy analysis demonstrated that the Ni surface phase of ALD(TiO2)-Ni/C mainly consisted of Ni(OH)2 while that of uncoated Ni/C was a mixed phase of NiO and Ni(OH)2. The ALD(TiO2)-Ni/C exhibited electrocatalytic activity at least 2.4 times higher than that of Ni/C. Density functional theory calculations were used to investigate how the modified Ni surface with the TiO2 coating affects the adsorption/desorption of glycerol.

A Group Additivity Based-Thermodynamic Analysis of a Conceptual Glycerol/Ferric Redox Flow Battery

The electrochemical oxidation of glycerol has been studied and known to be a source of several chemicals of premium industrial value and has also been utilized in the concept of direct glycerol fuel cells to produce electrical energy additionally[1]. In the current study however, this concept is extended to cover both electrochemical oxidation and reduction of glycerol as a substitute for the hydrogen ion in redox flow battery with a Fe2+/Fe3+ couple as cathode [2]. A predictive thermodynamic analysis has been developed and applied to the study and proof of this conceptual glycerol redox flow battery. Reactions toward electrochemical formation of several partial oxidation and reduction products of glycerol in acidic media under discharge and charging conditions of the proposed glycerol flow battery are presented. Free energy values of the reaction species as estimated by the Group Additivity Value (GAV) method were used to determine the feasibility of these proposed reaction towards cogeneration of electricity and commodity chemicals. The equilibrium voltages representing the maximum electrical work under these conditions are also computed. Experimental validation of this theoretical concept has also been investigated using electrochemical methods to study the electro-catalytic activity of electrolessly deposited NiCuSnP supported on carbon towards glycerol oxidation in acidic medium as anode in a proton exchange membrane-glycerol redox flow battery. Li W., Xin L., Zhang Z., Wang Z.,. (2012) Simultaneous Generation of Mesoxalic Acid and Electricity from Glycerol on a Gold Anode Catalyst in Anion-Exchange Membrane Fuel Cells ChemCatChem Vol 4 1105-1114Khalid Fatih K, Wilkinson D., Moraw F., Ilicic A and Girarda F Advancements in the Direct Hydrogen Redox Fuel Cell Electrochemical and Solid-State Letters, 11 2 B11-B15 (2008) Figure 1

Development of an electrochemical sensor for the determination of glycerol based on glassy carbon electrodes modified with a copper oxide nanoparticles/multiwalled carbon nanotubes/pectin composite

A very sensitive electrochemical sensor to determine glycerol (GLY) in biodiesel samples has been developed. It is based on the electrochemical oxidation of GLY at glassy carbon electrodes modified with copper oxide nanoparticles supported on multiwalled carbon nanotubes/pectin composite. The electrochemical oxidation of GLY was studied in pH 8 phosphate buffer solutions. The quantification of GLY was performed by amperometric measurements. The proposed electrochemical sensor improves the performance of others methods developed for the quantitation of GLY. A low limit of detection of 5.8×10−6g dm−3 and a percent coefficient of variation smaller than 10% was found, along with a reasonable linear range of 9×10−6–1×10−3g dm−3. The proposed electrochemical sensor exhibited good performance, stability, reproducibility, repetitiveness and a good detection limit and a linear concentration range to quantify GLY in biodiesel samples.

A Practical Approach in Glycerol Oxidation for the Development of A Glycerol Fuel Cell

The research on electrochemical carbon molecule oxidation started in the past years as new electrochemistries were researched for new fuel cells systems and batteries that may line up as backup energy supply and storage systems in off-grid and on-grid microgrids, as modeled by our group at the University of Twente [1-3]. By lining up these two disciplines we hope to support the bridge between new electrochemical systems on one side, (pilot) production with partner companies, prediction, and validation of systems upon implementation in microgrids by our group. The electrochemical oxidation of glycerol in alkaline aqueous solution has been studied on gold and gold coated metals (Zn-Au and Cu-Au) by voltammetry and EIS (Electrochemical impedance spectroscopy) for possible use in a new fuel cell as an outlet for the excess glycerol that is produced in the biodiesel industry. The observations show that the gold surface may change upon cycling by cyclic voltammetry. Besides, the current density shows non-linear behavior with the square root of the scan rate, implying that the reaction is not totally controlled by diffusion. EIS analysis using the EQUIVCRT software revealed that one out of twenty tested equivalent circuits fitted the data well at potentials of -0.05 V,- 0.15 V and -0.25 V vs. Ag/AgCl, identifying resistors and a Warburg element in parallel with the double layer capacitance, the elements are possibly related to the presence of double layers associated with hydroxypyrovate and oxalate ions. The results are consistent with the low-frequency error fitting analysis (10-4), AC Simulink-Matlab fitting responds and the Kronig-Kramers transform test. The tested Zn-Au and Cu-Au electrodes show similar voltammetry behavior as the gold electrode, as witnessed by the results of cycle analysis and the scan rate analysis. The discharge chronoamperometry test further shows that the Zn-Au electrode and Cu-Au have higher current densities than the gold electrode at a potential of -0.25 V vs. Ag/AgCl (5 mA cm-2, 4.5 mA cm-2, and 3 mA cm-2 respectively).

Polymer-immobilized, hybrid multi-catalyst architecture for enhanced electrochemical oxidation of glycerol

The development of a hybrid, tri-catalytic architecture is demonstrated by immobilizing MWCNTs, TEMPO-modified linear poly(ethylenimine) and oxalate decarboxylase on an electrode to enable enhanced electrochemical oxidation of glycerol. This immobilized, hybrid catalytic motif results in a synergistic 3.3-fold enhancement of glycerol oxidation and collects up to 14 electrons per molecule of glycerol.

Strong Impact of Platinum Surface Structure on Primary and Secondary Alcohol Oxidation during Electro-Oxidation of Glycerol

Herein we describe a combined experimental and computational study of electrochemical glycerol oxidation in acidic media on Pt(111) and Pt(100) electrodes. Our results show that glycerol oxidation is a very structure-sensitive reaction in terms of activity and, more surprisingly, in terms of selectivity. Using a combination of online HPLC and online electrochemical mass spectrometry, we show that on the Pt(111) electrode, glyceraldehyde, glyceric acid, and dihydroxyacetone are products of glycerol oxidation, while on the Pt(100) electrode, only glyceraldehyde was detected as the main product of the reaction. Density functional theory calculations show that this difference in selectivity is explained by different binding modes of dehydrogenated glycerol to the two surfaces. On Pt(111), the dehydrogenated glycerol intermediate binds to the surface through two single Pt–C bonds, yielding an enediol-like intermediate, which serves as a precursor to both glyceraldehyde and dihydroxyacetone. On Pt(100), the deh...

PtAu Electrocatalyst for Glycerol Oxidation Reaction Using a ATR-FTIR/Single Direct Alkaline Glycerol/Air Cell In Situ Study

Different ratios of PtAu/C electrocatalysts were synthesized and assessed for their capability by glycerol electrooxidation. Electrocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), cyclic voltammetry (CV), chronoamperometry, and direct glycerol/air fuel cell coupled with a ATR-FTIR setup. XRD of PtAu/C electrocatalysts showed the presence of Pt (fcc), Au (fcc), and PtAu (fcc) phases, and TEM images for PtAu/C electrocatalysts showed particle size between 5.4 and 5.8 nm. PtAu/C (50:50) presented the best result for glycerol electrooxidation by cyclic voltammetry and chronoamperommetry measurements in comparison with other electrocatalysts prepared. All PtAu/C showed better performance in comparison with Pt/C and Au/C. Moreover, the addition of gold to platinum favored glycerol by electronic effect and bifunctional mechanism. Through ATR-FTIR/direct alkaline glycerol/air cell in-situ study, it was possible to identify glycerate and tartronate as main products formed during the electrochemical glycerol oxidation.

Catalytic Design through Computational Modeling: Exploring the Electrochemical Oxidation of Glycerol By Nitroxyl Radical

Recently there has been an increased interest in the development of small molecule electrooxidation catalysts such as (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO), for use in the anodic compartment of a biofuel cell. Some TEMPO derivatives are capable of electrochemically oxidizing short chain alcohols and various sugars to the corresponding aldehydes and carboxylic acids under physiological aqueous conditions. However, building libraries of such a catalyst is difficult due to the limited number of commercially available TEMPO derivatives and the lack of modular synthetic pathways to more complicated TEMPO structures. A promising alternative to the physical preparation of such libraries is the use of computational modeling to allow for in silico catalytic screening of a much wider range of TEMPO compounds. We have developed a computational model based on simple geometry optimization and population analysis to probe the catalytic activity and oxidation potential of TEMPO-derived species. Redox potentials were calculated from the free energy cycle of TEMPO oxidation while the relative catalytic activity was modeled using multidimensional analysis involving the computed pKas of various protonation states of the hydroxylamine form of TEMPO along with the corresponding redox potentials. We will also discuss how analysis of the atomic polar tensor (APT) charge of TEMPO can provide insight into the factors that affect its redox potential.

Kinetic Investigations of Glycerol Oxidation Reaction on Ni/C

This study evaluates the electrochemical oxidation of glycerol using a nickel-supported catalyst under several well-defined experimental conditions. The influence of scan rate, temperature, glycerol, and NaOH concentrations were systematically investigated. The slope of the log-log relationship of the anodic peak current for glycerol oxidation as a function of the scan rate indicates that the electrochemical glycerol oxidation is a complex mechanism partially limited by diffusion-controlled process. This is in agreement with the temperature effect on glycerol oxidation, since the slope value associated with the relationship between the logarithm of the current density of the anodic peak and the inverse of temperature also indicates a diffusion process. When the glycerol concentration increases, the peak associated to its oxidation also increases, but it seems to reach a limit. This behavior was associated with two main effects, i.e., the saturation of the active catalytic sites on the electrode surface and the change in the glycerol oxidation mechanism as demonstrated by FTIR spectroscopic measurements.

Promotional Effect of Ag on the Catalytic Activity of Au for Glycerol Electrooxidation in Alkaline Medium

AbstractThe potential of silver as an auxiliary metal for gold in the electrochemical oxidation of glycerol in alkaline medium is studied. Three bimetallic materials (Au3Ag/C, AuAg/C, and AuAg3/C) and the corresponding monometallic reference materials (Au/C and Ag/C) are prepared by chemical reduction of their precursors with glycerol. Half‐cell measurements evidence the beneficial effect of Ag on the electrocatalytic activity of Au for glycerol oxidation owing to decreased onset potential and higher current density in chronoamperometry, with an optimum formulation of AuAg/C. These results are confirmed by the single‐cell performance of AuAg/C, which, despite having half the Au loading, has a higher open‐circuit voltage than Au/C and a similar maximum power density. The results are correlated with the structural and electronic features of these materials, which are widely discussed in other works.

Effect of Nanometallic Catalysts on Electrochemical Oxidation of Glycerol

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