Glycerol Electrooxidation Research Articles

Anodic glycerol oxidation to formate facilitating cathodic hydrogen evolution with earth-abundant metal oxide catalysts

Substituting sluggish oxygen evolution reaction (OER) with glycerol electrooxidation reaction (GER) to formate is a promising strategy for addressing glycerol overproduction and hydrogen production efficiency concurrently. However, the poor formate selectivity and the use of noble-metal catalysts hamper electrolysis applications of glycerol. Herein, we present a commercial nickel foam-supported nickel cobaltite (NiCo2O4/NF) synthesized via a facile hydrothermal/annealing combined process. The as-synthesized earth-abundant metal oxide composite enables anodic GER to formate, achieving not only as low as potential of 1.23 V (vs. reversible hydrogen electrode, RHE) to deliver 10 mA cm−2, but also a large catalytic current density of 152 mA cm−2 with an exceeding formate faradic efficiency (FE) of 97 % at 1.6 V (vs. RHE). Synergy effect induced by intermetallic interactions of hierarchical NiCo2O4 nanostructures rooted in Ni foam substrate facilitates anodic oxidation of glycerol and assists cathodic hydrogen production simultaneously. In particular, a two-electrode electrolyser NiCo2O4/NF || Ni foam requires a cell voltage of as low as 1.35 V to achieve 10 mA cm−2, which is 320 mV lower than that of the conventional overall water splitting systems.

Replacing oxygen evolution reaction by glycerol electrooxidation on Rh modified Ni(OH)2/C for energy-efficient hydrogen production

Oxygen evolution reaction (OER) is a key reaction for the development of green and sustainable energy system based in the production of hydrogen by electrolysis. However, the water splitting required a high overpotential for the oxygen evolution reaction. In this work we investigated the use of the Glycerol Electrooxidation Reaction (GEOR) in alkaline solutions on Rh/C, Ni(OH)2/C and Rhx{Ni(OH)2}y/C nanocomposites instead of water as a reagent in the anodic reaction in electrolyzers as a way to reduce the cell overpotential and obtain energy savings. The electrocatalysts were prepared by microwave-assisted alcohol reduction method and characterized by X-ray diffraction. The catalysts presented particles with fcc structure for Rh/C, a hexagonal structure for (Ni(OH)2/C), and (Rh0.3{Ni(OH)2}0.7/C) and (Rh0.5{Ni(OH)2}0.5/C) presented mixed structures with brucite and a α-Ni(OH)2/C structure. The electrochemical performance of Rh0.3{Ni(OH)2}0.7/C presented superior density current at low potential in comparison to the other studied materials. The potential value determined for GEOR at 10 mA cm−2 was nearly 1.29 V vs. RHE in a 0.5 mol L−1 glycerol solution that is 0.3 V less than the value obtain Rh/C in the absence on the organic species. The analysis of the products generated after bulk electrolysis using high-performance liquid chromatography demonstrated that at 1.50 V vs. RHE the main reaction products were and tartronate, glyceraldehyde and oxalate, depending on the employed catalytic material. These results demonstrated that value-added products could be obtained as a promising way to valorize by the glycerol electrooxidation besides the energy saving during the electrolysis for the hydrogen production.

Photoassisted Strategy to Promote Glycerol Electrooxidation to Lactic Acid Coupled with Hydrogen Production

Electrocatalytic oxidation of glycerol (GLY; from a biodiesel byproduct) to lactic acid (LA; the key monomers for polylactic acid; PLA) is considered a sustainable approach for biomass waste upcycling and is coupled with cathodic hydrogen (H2) production. However, current research still suffer from issues of low current density and low LA selectivity. Herein, we reported a photoassisted electrocatalytic strategy to achieve the selective oxidation of GLY to LA over a gold nanowire (Au NW) catalyst, attaining a high current density of 387 mA cm-2 at 0.95 V vs RHE, together with a high LA selectivity of 80%, outperforming most of the reported works in the literature. We reveal that the light-assistance strategy plays a dual role, which can both accelerate the reaction rate through the photothermal effect and also promote the adsorption of the middle hydroxyl of GLY over Au NWs to realize the selective oxidation of GLY to LA. As a proof-of-concept, we realized the direct conversion of crude GLY that was extracted from cooking oil to attain LA and coupled it with H2 production using the developed photoassisted electrooxidation process, revealing the potential of this strategy in practical applications.

Electrolysis of Glycerol by Non-Noble Metal Hydroxides and Oxides

A series of free-standing electrodes consisting of hydroxides (Ni(OH)2, Co(OH), NiFeLDH, and CoFeLDH) and oxides (NiO, Co3O4, NiFe2O4, and CoFe2O4) supported by carbon paper were fabricated via an in situ hydrothermal process and further examined for glycerol conversion. The morphology and structures of the samples were characterized by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The performance of the samples was studied by cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy. The products of glycerol oxidation were analyzed by high-performance liquid chromatography. Operando electrochemical Raman spectroscopy was employed to monitor the variations on the active sites and intermediates. Among the samples, the NiO exhibited superior activity with the largest current density of 0.8 mA cm–2 at 1.7 V and selectivity of 97% for formic acid. Furthermore, coupling the hydrogen evolution reaction with the glycerol electro-oxidation reaction (GOR), we explored the electrolysis of water and glycerol. The potential of the electrolysis process was negatively shifted from 1.68 to 1.28 V by replacing the oxygen evolution reaction with GOR. The strategy reported in this work could afford a sustainable approach to produce hydrogen and value-added chemicals with high energy efficiency.

Operando Revealing the Crystal Phase Transformation and Electrocatalytic Activity Correlation of MnO2 toward Glycerol Electrooxidation

In this work, we report for the first time a comprehensive operando investigation of the intricate correlation between dynamic phase evolution and glycerol electrooxidation reaction (GEOR) performance across three primary MnO2 crystallographic phases (α-, β-, and γ-MnO2). The results showed that all three electrocatalysts exhibited comparable selectivity toward three-carbon products (∼90%), but γ-MnO2 exhibited superior performance, with a low onset potential of ∼1.45 VRHE, the highest current density of ∼1.9 mA cm-2 at 1.85 VRHE, and reasonable stability. Operando Raman spectroscopy revealed the potential-induced surface reconstruction of different MnO2 structures from which a correlation among the applied potential, electrocatalytic activity, and product distribution was identified. The higher the applied potential, the greater conversion from the original structure to δ-MnO2, resulting in lower C-C cleavage and higher 3C product selectivity. This study not only provides a systematic understanding of structure-controlled electrocatalytic activity for high selectivity toward 3C products of MnO2 but also contributes to the development of a non-noble and environmentally friendly catalyst for valorizing glycerol.

Organic interfacial engineering of gold nanowires for selective glycerol electrooxidation

The selective electrochemical conversion of glycerol into value-added products is a green and sustainable strategy for the biomass utilization. In this work, Au nanowires (Au-NW) modified with polyethyleneimine (PEI) molecule (Au-NW@PEI) is obtained by an up-bottom post-modification approach. Physical characterization, molecular dynamics simulation and density functional theory demonstrate that the loose-packed PEI monolayer firmly and uniformly distribute on the Au-NW surface due to the strong Au-N interaction. Electrochemical experiments and product analysis display that PEI modification significantly enhance the electro-activity of Au-NW for the glycerol electro-oxidation reaction (GEOR) due to the electronic effect. Meanwhile, the steric hindrance and electrostatic effect of PEI layer make the optimizing adsorption of intermediates possible. Therefore, the selectivity of C3 product glyceric acid over Au-NW@PEI is increased by nearly 20%. The work thus indicates that the rational design of metal-organic interface can effectively elevate the electro-activity and selectivity of Au nanostructures, which may have wide application in biomass development.

Glycerol Electro-Oxidation in Alkaline Medium with Pt-Fe/C Electrocatalysts Synthesized by the Polyol Method: Increased Selectivity and Activity Provided by Less Expensive Catalysts.

We have investigated platinum catalysts containing iron as a modifier to obtain catalysts with superior electrocatalytic activity toward glycerol electro-oxidation in an alkaline medium. The electrocatalysts, supported on carbon Vulcan, were synthesized by the polyol method. The physicochemical characterization data showed that the metals were well distributed on the carbon support and had small particle size (2 nm). The Pt:Fe metal ratio differed from the nominal composition, indicating that reducing iron with platinum was difficult, even though some parameters of the synthesis process were changed. Electrochemical analyses revealed that PtFe/C was more active and stable than commercial Pt/C was, and analysis of the electrolysis by-products showed that iron addition to Pt/C boosted the glycerol conversion and selectivity for glyceric acid formation.

Bimetallic PtCu/C Catalysts for Glycerol Assisted Hydrogen Evolution in Acidic Media

Glycerol electrooxidation is a promising alternative to oxygen evolution as an anodic reaction for efficient hydrogen production. However, the performance of electrocatalysts in this reaction is still limited by CO poisoning and products of lower value form due to C−C cleavage. In this study, PtCu/C catalysts with different metal ratios were investigated for glycerol electrooxidation in acidic media. The addition of Cu to the benchmark Pt/C catalyst increased the activity, productivity, as well as stability due to electronic and structural effects. The best performer Pt7Cu3/C showed an increase in mass activity of 56 %. Lower accumulation of intermediates was proven in electrolysis experiments, leading to an increased selectivity of 90 % to valuable C3-products. The combined methodology of comprehensive electrochemical characterization and application in electrolysis experiments provides a practical approach for improving glycerol assisted hydrogen production addressing major challenges such as CO poisoning and stability.

Continuous carbon dioxide electroreduction to formate coupled with the single-pass glycerol oxidation to high value-added products

CO2 electroreduction has been considered a promising alternative to simultaneously reduce CO2 emissions and produce value-added products. Among others, the production of formic acid/formate is particularly attractive. Although promising results have already been obtained in the literature, one of the recent approaches to improve the process deals with the use of an alternative reaction at the anode instead of the traditional oxygen evolution reaction (OER). In this context, this work reports, for the first time, the study of the CO2 electroreduction to formate coupled with the electrooxidation of glycerol to high-added value products where both half-reactions operate in a continuous mode with a single pass of the reactants through the electrochemical cell. Interestingly, at the cathode, similar results to those previously reported were obtained, reaching formate concentrations of about 18 g·L-1 at a 200 mA·cm-2. In addition, at the anode, promising dihydroxyacetone productions of 196 µmol·m-2·s-1 were simultaneously achieved in the output stream of the anodic compartment. These findings represent a significant step forward for the development and application of the technology.

How does CO co-adsorption affect glycerol electro-oxidation on polycrystalline platinum? in situ FTIR and DFT approaches

After decades of studies and countless works, the scientific community is still debating whether the presence of adsorbed CO is a necessary step in the reaction pathways of electro-oxidation mechanisms or whether CO is a species to be avoided because of its stability as a reaction intermediate. In order to shed some light on the role of CO as a reactive adsorbate, in the present work we investigated how the co-adsorption of CO (externally supplied) affects the electro-oxidation of glycerol on a polycrystalline platinum surface. Cyclic voltammetry, in situ FTIR (with isotopically labeled glycerol) and DFT results suggest that the ability of the surface to oxidize adsorbed species is closely linked to the number of free surface sites for water adsorption. Specifically, the adsorption of CO is favored over glycerol, which implies that even when this species is put into contact with a glycerol pre-adsorbed layer (on platinum), CO is able to adsorb in domains with few free sites and even displace previously adsorbed molecules. Therefore, the glycerol electro-oxidation reaction is partially inhibited.

Rare-earth modified platinum-based electrocatalysts incorporating anodic glycerol oxidation reactions while promoting cathodic hydrogen evolution reactions

Glycerol electrooxidation (GOR) is a safe and clean method for conversion of glycerol. In the course of this work, a series of PtxCe/C catalysts have been synthesized by successive polyol reduction methods as well as etching and calcination. Various physicochemical characterrisation and electrochemical measurements have demonstrated the excellent performance of Pt3Ce/C composites in glycerol oxidation (GOR) and hydrogen evolution reactions (HER). The Pt3Ce/C catalyst showed better performance in GOR and HER compared to commercially available Pt/C electrocatalysts. This paper demonstrates an energy efficient electrocatalyst for the simultaneous precipitation of hydrogen from glycerol oxidation.

Tailor-designed binary Ni-Cu nano dendrites decorated 3D-carbon felts for efficient glycerol electrooxidation.

Herein, 3D-Carbon Felt (CF) are decorated with nickel-copper (Ni-Cu@CF) bimetallic nanostructures through either sequential or co-electrodeposition tactics. Their catalytic activity towards glycerol electrooxidation is investigated by employing cyclic voltammetry (CV) and linear sweep voltammetry LSV. The morphology and composition of the various Ni-Cu@CF are investigated using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) together with various electrochemical measurements (e.g., CV, chronoamperometry, LSV). The co-deposition of Ni-Cu shows a dendritic-like structure with higher electrocatalytic activity towards glycerol electrooxidation compared to the monometallic counterparts. Interestingly, the best electrode (NiCu@CF Ni particles as the top layer) prepared by sequential electrodeposition shows 1.6-fold higher glycerol oxidation activity, manifested in oxidation current, compared to Ni-coated CF due to Ni particles covering the surface of dendritic copper uniformly. Thus, the surface concentration of Ni is increased and at the same time a synergistic effect occurs between Ni and Cu by the simple addition of Cu which reinforces the surface concentration of Ni from 3.4 × 10-8 to 1.1 × 10-7 mol cm-2.

Effect of pore mesostructure on the electrooxidation of glycerol on Pt mesoporous catalysts

Valuable chemicals such as glycerate, in addition to hydrogen, can be obtained from the controlled electrooxidation of glycerol using suitable highly active, mesoporous platinum catalysts.

Electrocatalytic Activities of a Platinum Nanostructured Electrode Modified by Gold Adatom toward Methanol and Glycerol Electrooxidation in Acid and Alkaline Media.

For practical applications such as fuel cells, it is important to exploit electrocatalysis with high activity for methanol and glycerol oxidation. A platinum nanostructured electrode (PtNPs) is modified by gold adatoms and is created by application of a square wave potential regime to a tantalum surface electrode. In nanostructured platinum, the structure and the surface properties are characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and cyclic voltammetry (CV). In acid and alkaline media, the CV and Chronoamperometric (CA) are studied to investigate the catalytic activity of the PtNPs nanoparticles for the electrooxidation of methanol and glycerol. The prepared nanostructured platinum on a tantalum electrode was allowed to balance an open circuit with a 1.0×10-3 M solution containing an Au ion. Consequently, the proximity of the irreversibly adsorbed Au-adatoms on the already described Pt-nanostructured electrode. In acidic and alkaline solutions, the electrocatalytically activities toward methanol and glycerol oxidation were evaluated and is found to strongly on the surface of the gold-modified PtNPs. The PtNPs modified by Au electrode system used direct methanol fuel cell (DMFC) and direct glycerol fuel cell (DGFC). The DMFC and DGFC are much higher than in acid output in alkaline. Comparison of the i-E curves of nanostructure platinum electrode with that of a platinum nanostructure electrode modified by Au under similar conditions for the letter, the charge under the peak (i-E curve) in the oxidation region was higher. Furthermore, rough chronoamperometric measurements confirmed the results. The results of showed that the electrocatalytic properties of the nanostructured prepared surface were enhanced by the inclusion of gold adatoms with a variable extent of advancement. The current peak (Ip) and the current chronoamperometric (ICA) of glycerol oxidation on the PtNPs electrode modified by Au in acid media (130 mA/cm2, 47 µA/cm2) were higher than those of the bare PtNPs electrode and in alkaline media (171 mA/cm2, 66 µA/cm2). The stronger catalytic behavior in alkaline media of the Au-PtNP electrode indicates its promising use in alkaline direct alcohol cells.

Enhancing the performance of Ni nanoparticle modified carbon felt towards glycerol electrooxidation: impact of organic additive.

Organic additives are widely used in the deposition baths of metals and alloys thanks to their special function which affects the growth and the building of the crystal. This study investigates the effect of glycerol on Ni deposition onto carbon felt (CF) and its effect on the catalytic activity towards glycerol electrooxidation. The impact of glycerol on the morphology, distribution, and particle size of the electrodeposited Ni is disclosed using a scanning electron microscope (SEM). X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV) techniques were used to probe the possible changes of the electrodeposited Ni oxide phases. Electrochemical measurements show that the as-synthesized Ni0.05@CF electrocatalyst prepared in the presence of 50 mM glycerol has a marked activity towards glycerol electrooxidation, as confirmed by the impressive increase of the oxidation current by about 1.6 times concurrently with a favorable negative shift of its onset potential. Moreover, the charge transfer resistance (R ct) is much reduced from 140 to 87 ohm. The addition of glycerol to the deposition bath is believed to retard the growth of the formed Ni deposits while enhancing the nucleation rate and thus increases the particle density and, consequently, the distribution of deposited Ni over the entire CF is improved along with increasing the surface concentration and surface-active sites. This assumption is supported by density functional theory (DFT) calculations.

Au@NiSx Yolk@Shell Nanostructures as Dual‐Functional Electrocatalysts for Concomitant Production of Value‐Added Tartronic Acid and Hydrogen Fuel (Adv. Funct. Mater. 4/2023)

Glycerol Electrooxidation In article number 2209386, Yung-Jung Hsu, Chia-Ying Chiang, and co-workers demonstrate practical use of Au@NiSx yolk@shell nanostructures for efficient glycerol electrooxidation (GEOR). Further integration of GEOR with hydrogen evolution reaction is realized by employing Au@NiSx as both anode and cathode electrocatalysts in a two-electrode configuration. Concomitant production of tartronic acid, one of the highest value-added intermediates, and hydrogen fuel can be accomplished.

Yttrium-doped cobalt-based metal-organic frameworks for selective electrooxidation of glycerol coupled with hydrogen production.

A facile strategy was developed for one-step synthesis of yttrium(Y)-doped cobalt-based metal-organic framework (CoY-MOF) nanosheet arrays. It was demonstrated that in situ doping with a low content of Y can tailor the electronic structure of the MOF structures, thereby improving their electrocatalytic performance for both hydrogen evolution and glycerol oxidation reactions.

Porous gold-curcumin nanocomposite for enhanced electrooxidation of glycerol and ethylene glycol

• Electrodeposited a thin film of gold-curcumin nanocomposite on the surface of GCE using a galvanostatic current. • Electrocatalytic oxidation of Gly and EG with a low activation energy of 20.7 and 49.7 kJ mol −1 , respectively. • Low onset potential during electrooxidation of Gly and EG at −0.17 V and −0.14 V, respectively. We report efficient electrocatalytic oxidation of glycerol (Gly) and ethylene glycol (EG) using a thin film of gold-curcumin (Au-CM) nanocomposite deposited on a glassy carbon electrode. The nanocomposite was synthesized using a galvanostatic technique in a two-electrode system with a very low current of 0.5 mA. Extensive characterization confirmed that the deposit consists of gold nanoparticles in a porous curcumin envelope. The Au-CM/GCE showed excellent catalytic activity for the electrocatalytic oxidation of Gly and EG with a low activation energy of 20.7 and 49.7 kJ mol –1 and a low onset potential of –0.17 V and –0.14 V, respectively.

Electro-oxidation of glycerol over Sb-modified Pt (1 0 0) preferentially oriented nanoparticles

The glycerol electro-oxidation reaction (GEOR) has been studied in recent decades, which is justified by its potential use in direct alcohol fuel cells and electrolyzers. Since GEOR is sensitive to the structure, its mechanistic aspects are not directly transferable from model surfaces to nanoparticles used in applied systems. Therefore, in this work we synthesized preferentially oriented Pt nanoparticles, which constitute a bridge between the molecular information that can be extracted from single crystals and the practical potential of nanoparticles. Specifically, (100) preferentially oriented Pt nanoparticles were decorated with different Sb contents and tested for GEOR. Our results suggest that (100) domains are the most affected by Sb. This selective adsorption, in turn, has a profound impact on GEOR, since those electro-oxidation pathways that depend on prior molecular fragmentation are strongly inhibited by Sb.

Quantification of electron transfer on carbon nanotubes: Effect of edge defects on electro-oxidation of glycerol catalyzed by platinum

It is still an ongoing challenge to quantitatively determine the number of transferred electrons from carbon supports to metallic catalysts, which is highly related to their catalytic performance. In this work, a facile method combining electrochemical and spectroscopic technologies was proposed to evaluate the electron transfer (ET) reaction rate on carbon nanotubes (CNTs) with defects. Using 7,7,8,8-tetracyanoquinonedimethane (TCNQ) as an electron-accepting molecule, the transferred electrons from CNTs were quantitatively determined through the Beer-Lambert law and coulometric analysis. It was revealed that the edge defects on CNTs are beneficial for the ET reaction rate, due to the lower local work function. Hence, the defective CNTs supported Pt nanoparticles (Pt/d-CNTs) performed the higher activity in the electrooxidation of glycerol, suggesting the influence of the ET ability of d-CNTs on the electronic metal-support interaction. This scenario is supported by density function theory calculation and X-ray photoelectron spectroscopy. Our results pave a new way to the facile evaluation of electronic metal–carbon interaction.