Ethanol Oxidation Reaction Research Articles

Effect of deposition potential and KOH concentration on ethanol oxidation reaction with Pd nanoparticles electrodeposited on glassy carbon from reline

Pd nanoparticles (PdNPs) are deposited electrochemically on the glassy carbon electrode surface using PdCl2 dissolved in a deep eutectic solvent composed of choline chloride and urea (reline). The morphology and particle size of the PdNPs are determined from SEM exhibiting a homogeneous distribution with potential deposition depending on particle size. The particles display a core-shell morphology, consisting of Pd(0) as the core and Pd(OH)2 as the shell. The ethanol oxidation reaction, EOR, is evaluated at different KOH concentrations. The electrocatalyst with the highest mass activity is achieved at −750 mV potential deposition and 1 M KOH, exhibiting 3126 ± 606 mAmgPd−1. However, when 0.1 M KOH is used the mass activity decreases to one-third the value obtained at 1 M KOH. Notwithstanding, the mass activity displayed by these PdNPs is superior to that reported for other Pd-based nanoparticles synthesized using more complex, time-consuming and costly methods reported in the literature.

Simply prepared α-Ni(OH)2-based electrode for efficient electrocatalysis of EOR and OER

As one of the most efficient Ni phases towards ethanol oxidation reaction (EOR), α-Ni(OH)2 is aimed to be simply prepared. Various α-Ni(OH)2-rich deposits are obtained chronoamperometrically from NiCl2 solution onto a pristine graphite surface at different potentials. After careful optimization, the optimum values deposition potential and time are found to be -0.9 V and 150 s, respectively. At longer deposition times, the predominant component of the deposits is the β-Ni(OH)2 phase. The optimum electrode, Ni(OH)2/G(opt), exhibits remarkable EOR catalytic activity with an ethanol oxidation peak current of 325.35 mA/cm2. Moreover, Ni(OH)2/G(opt) demonstrates noteworthy activity and durability for oxygen evolution reaction (OER) in 1 M NaOH. Whereas the overpotential at current density of 10 mA/cm2 (ηt=0) is 0.37 V; however, after 24 h it slightly increases to (ηt=24h) 0.39 V. These values imply significant outcomes for our novel and straightforward preparation method for creating highly efficient electrocatalysts for both EOR and OER using time- and cost-effective materials.

Solvothermal synthesis of PdCu nanorings with high catalytic performance for alcohol electrooxidation

Two-dimensional (2D) Pd-based nanostructures with a high active surface area and a large number of active sites are commonly used in alcohol oxidation research, whereas the less explored ring structure made of nanosheets with large pores is of interest. In this study, we detail the fabrication of PdCu nanorings (NRs) featuring hollow interiors and low coordinated sites using a straightforward solvothermal approach. Due to increased exposure of active sites and the synergistic effects of bimetallics, the PdCu NRs exhibited superior catalytic performance in both the ethanol oxidation reaction (EOR) and the ethylene glycol oxidation reaction (EGOR). The mass activities of PdCu NRs for EOR and EGOR were measured at 7.05 A/mg and 8.12 A/mg, respectively, surpassing those of commercial Pd/C. Furthermore, the PdCu NRs demonstrated enhanced catalytic stability, maintaining higher mass activity levels compared to other catalysts during stability testing. This research offers valuable insights for the development of efficient catalysts for alcohol oxidation.

2D PtRhPb Mesoporous Nanosheets with Surface-Clean Active Sites for Complete Ethanol Oxidation Electrocatalysis.

The development of active and selective metal electrocatalysts for complete ethanol oxidation reaction (EOR) into desired C1 products is extremely promising for practical application of direct ethanol fuel cells. Despite some encouraging achievements, their activity and selectivity remain unsatisfactory. In this work, it is reported that 2D PtRhPb mesoporous nanosheets (MNSs) with anisotropic structure and surface-clean metal siteperform perfectly for complete EOR electrocatalysis in both three-electrode and two-electrode systems. Different to the traditional routes, a selective etching strategy is developed to produce surface-clean mesopores while retaining parent anisotropy quasi-single-crystalline structure without the mesopore-forming surfactants. This method also allows the general synthesis of surface-clean mesoporous metals with other compositions and structures. When being performed for alkaline EOR electrocatalysis, the best PtRhPb MNSs deliver remarkably high activity (7.8 A mg-1) and superior C1 product selectivity (70% of Faradaic efficiency), both of which are much better than reported electrocatalysts. High performance is assigned to multiple structural and compositional synergies that not only stabilized key OHads intermediate by surface-clean mesopores but also separated the chemisorption of two carbons in ethanol by adjacent Pt and Rh sites, which facilitate the oxidation cleavage of stable C─C bond for complete EOR electrocatalysis.

Competitive intermetallics formation in Pd-Zn-Cd system via seeded growth from ultra-thin Pd nanosheets for electrocatalytic ethanol oxidation reaction

Competitive intermetallics formation in Pd-Zn-Cd system via seeded growth from ultra-thin Pd nanosheets for electrocatalytic ethanol oxidation reaction

Oxygenate-induced structural evolution of high-entropy electrocatalysts for multifunctional alcohol electrooxidation integrated with hydrogen production

High-entropy compounds have been emerging as promising candidates for electrolysis, yet their controllable electrosynthesis strategy remains a formidable challenge because of the ambiguous ionic interaction and codeposition mechanism. Herein, we report a oxygenates directionally induced electrodeposition strategy to construct high-entropy materials with amorphous features, on which the structural evolution from high-entropy phosphide to oxide is confirmed by introducing vanadate, thus realizing the simultaneous optimization of composition and structure. The representative P-CoNiMnWVOx shows excellent bifunctional catalytic performance toward alkaline hydrogen evolution reaction and ethanol oxidation reaction (EOR), with small potentials of -168 mV and 1.38 V at 100 mA cm-2, respectively. In situ spectroscopy illustrates that the electrochemical reconstruction of P-CoNiMnWVOx induces abundant Co-O species as the main catalytic active species for EOR and follows the conversion pathway of the C2 product. Theoretical calculations reveal the optimized electronic structure and adsorption free energy of reaction intermediates on P-CoNiMnWVOx, thereby resulting in a facilitated kinetic process. A membrane-free electrolyzer delivers both high Faradaic efficiencies of acetate and H2 over 95% and superior stability at100 mA cm-2 during 120 h electrolysis. In addition, the unique composition and structural advantages endow P-CoNiMnWVOx with multifunctional catalytic activity and realize multipathway electrosynthesis of formate-coupled hydrogen production.

Tensile Strain and Interatomic Orbital Hybridization Effects Boost the Electrocatalytic Performance of Intermetallic Pd3Pb Nanowires for Ethanol Electrooxidation†

Comprehensive SummaryWe present a strategy that effectively modulate the d‐band electronic structure of the active center by strain effect and interatomic orbital hybridization. This strategy efficiently promotes the kinetic process of the ethanol oxidation reaction (EOR) in alkaline media. In the intermetallic Pd3Pb nanowires, the introduction of Pb not only causes the lattice expansion of Pd but also achieves the interatomic orbital hybridization bonding with Pd. Such interatomic orbital hybridization effect and tensile strain effect can effectively achieve a co‐regulation of the d‐band electronic structure of Pd, which directly affects the adsorption behavior of intermediate on Pd for EOR. Hence, the intermetallic Pd3Pb nanowires demonstrate enhanced EOR activity and anti‐poisoning ability against COads. Theoretical calculations show that the enhanced OH* adsorption ability and the low energy barrier for the oxidative dehydrogenation of ethanol are the keys to high EOR activity and stability of the intermetallic Pd3Pb nanowires.

Graphitic Carbon Nitride as a Promising Visible-Light-Activated Support Boosting Platinum Nanoparticle Activity in Ethanol Electrooxidation.

In the present work, exfoliated graphitic carbon nitride (g-CN) is immobilized on carbon paper substrates by a simple electrophoretic route, and subsequently decorated with ultra-low amounts (≈μg/cm2) of Pt nanoparticles (NPs) by cold plasma sputtering. Optimization of preparative conditions allowed a fine tuning of Pt NPs size, loading and distribution and thus a controlled tailoring of g-CN/Pt interfacial interactions. Modulation of such features yielded g-CN-Pt-based anode materials with appealing activity and stability towards the ethanol oxidation reaction (EOR) in alkaline aqueous solutions, as revealed by electrochemical tests both in the dark and under irradiation. The present results provide new insights on the design of nano-engineered heterocomposites featuring improved performances thanks to Pt coupling with g-CN, a low-cost and environmentally friendly visible light-active semiconductor. Overall, this work might open attractive avenues for the generation of green hydrogen via aqueous ethanol electrolysis and the photo-promoted alcohol electrooxidation in fuel cells.

Plasmon-enhanced electrocatalytic ethanol oxidation over Au@Pd nanostars

Hybrid noble-metal nanostructures, which integrate plasmonic characteristics and electrocatalytic performance, have garnered significant interest recently. In this study, Au@Pd nanostars were synthesized and employed as an advanced electrocatalyst for the ethanol oxidation reaction (EOR), which suffers from the kinetic limitations of the anodic half-reaction of direct ethanol fuel cells. Leveraging the superior surface plasmon resonance (SPR) property of Au nanostars, the synthesized Au@Pd nanostars exhibited superior plasmon-enhanced EOR activity of 4191.63 A g−1 under laser illumination, noting a 9.40-fold increase compared to dark conditions (445.99 A g−1). The influences of Pd loading and laser power on EOR activity were explored. The impact of Pd loading on EOR activity demonstrates a volcano-shaped correlation, where optimal Pd coverage enhances catalysis but excessive amounts dampen SPR performance, crucial for maximizing EOR activity. Within a specified range, EOR activity linearly increases with laser power due to its influence on SPR performance. Mechanistic investigation suggests the critical roles of photothermal effect and hot carriers’ separation in boosting EOR kinetics. The repeated experiments show little difference, ensuring the accuracy and reproducibility of the reported activity of Au@Pd nanostars for EOR. During the long-term stability estimation, the Au@Pd nanostars display the best durability over three electrocatalysts. Overall, our findings highlight the potential of plasmon-enhanced catalysis in advancing the performance of electrocatalysts for EOR and other conventional electrocatalytic reactions.

Investigation of an Ethanol Electroreforming Cell Based on a Pt1Ru1/C Catalyst at the Anode

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.

Systematic combination of palladium facets and monolayer metal hydroxide nanosheets for promotion of ethanol oxidation reaction

The design of catalyst surfaces that exhibit high activities for ethanol oxidation reaction (EOR) is essential to achieving practical application of direct ethanol fuel cells. Composite catalysts of Pd nanoparticles and metal hydroxide are promising candidates for EOR; however, a guide of catalyst design, including appropriate valence states and interfacial structures between component materials, has not been identified. Herein, we synthesize composite electrocatalysts of cubic and octahedral Pd nanocrystals with well-defined facets and monolayer metal hydroxide nanosheets with an identical structure and different composition containing Ni, Fe and Mn, and systematically elucidate highly active interfacial sites between Pd and metal hydroxides for EOR. Promotion of OH− adsorption by the hydroxide nanosheets enhances the catalytic activities of the Pd nanocrystals and the nanosheet having higher affinity to OH− result in higher EOR performances of the composite catalysts. The improved activities are greater for (111) facet than for (100) facet of the Pd whereas the (100) facet is superior for EOR to the (111) facet for the bare Pd nanocrystals. Our study suggests that combination of the Pd (111) facet and metal hydroxides is favorable for developing highly active electrocatalysts for EOR.

Locally Varying Surface Binding Affinity on Pd-Au Nanocrystals Enhances Electrochemical Ethanol Oxidation Activity.

Noble metal nanocrystals face challenges in effectively catalyzing electrochemical ethanol oxidation reaction (EOR)-represented multistep, multielectron transfer processes due to the linear scaling relationship among binding energies of intermediates, impeding independent optimization of individual elemental steps. Herein, we develop noble metal nanocrystals with a range of local surface binding affinities in close proximity to overcome this challenge. Experimentally, this is demonstrated by applying tensile strain to a Pd surface and decorating it with discrete Au atoms, forming a diversity of binding sites with varying affinities in close proximity for guest molecules, as evidenced by CO probing and density functional theory calculations. Such a surface enables reaction intermediates to migrate between different binding sites as needed for each elemental step, thereby reducing the energy barrier for the overall EOR when compared to reactions at a single site. On these tailored surfaces, we attain specific and mass activities of 32.7 mA cm-2 and 47.8 A mgPd-1 in EOR, surpassing commercial Pd/C by 10.9 and 43.8 times, respectively, and outperforming state-of-the-art Pd-based catalysts. These results highlight the promise of this approach in improving a variety of multistep, multielectron transfer reactions, which are crucial for energy conversion applications.

Au enables PdAu aerogel efficient catalysts for oxygen reduction and C2 alcohol oxidation

Metallic aerogels (MAs) with self-supporting three-dimensional (3D) porous structures constitute a potential platform for the construction of robust catalysts. In this work, we successfully constructed 3D PdAu MAs with the optimized d-band electron of Pd and geometrical lattice expansion using a maneuverable in-situ seed-mediated strategy at room temperature. The introduction of Au accelerated the kinetics of Pd4Au3 MAs toward oxygen reduction reaction (ORR), ethylene glycol oxidation reaction (EGOR), and ethanol oxidation reaction (EOR) in alkaline electrolyte, boosting the activity and stability of Pd4Au3 MAs. The mass activities of Pd4Au3 MAs/C in ORR, EGOR and EOR were 1.74, 8.57, and 9.54 A mgPd−1, respectively, which were remarkably better than those of referenced Pd MAs/C, commercial Pt/C and Pd/C. The rotating ring-disk electrode measurement illustrated that Pd4Au3 MAs/C achieved a 4-electron transfer process in ORR from O2 to OH−. In-situ Fourier transform infrared spectroscopy revealed that Pd4Au3 MAs/C enabled the cleavage of the C–C bonds, thus accomplishing the C1-complete oxidation of 10-electron ethylene glycol and 12-electron ethanol. This study provides an efficient strategy to fabricate binary non-Pt alloy aerogels as high-performance multifunctional electrocatalysts for ORR, EGOR, and EOR.

Regioselective epitaxial growth of metallic heterostructures.

Constructing regioselective architectures in heterostructures is important for many applications; however, the targeted design of regioselective architectures is challenging due to the sophisticated processes, impurity pollution and an unclear growth mechanism. Here we successfully realized a one-pot kinetically controlled synthetic framework for constructing regioselective architectures in metallic heterostructures. The key objective was to simultaneously consider the reduction rates of metal precursors and the lattice matching relationship at heterogeneous interfaces. More importantly, this synthetic method also provided phase- and morphology-independent behaviours as foundations for choosing substrate materials, including phase regulation from Pd20Sb7 hexagonal nanoplates (HPs) to Pd8Sb3 HPs, and morphology regulation from Pd20Sb7 HPs to Pd20Sb7 rhombohedra and Pd20Sb7 nanoparticles. Consequently, the activity of regioselective epitaxially grown Pt on Pd20Sb7 HPs was greatly enhanced towards the ethanol oxidation reaction; its activity was 57 times greater than that of commercial Pt/C, and the catalyst showed increased stability (decreasing by 16.3% after 2,000 cycles) and selectivity (72.4%) compared with those of commercial Pt/C (56.0%, 18.2%). This work paves the way for the design of unconventional well-defined heterostructures for use in various applications.

Tailored PEO synthesis and in-situ ATR-FTIR study of PtSnO2/Nb coral-like structures for application in ethanol electrooxidation

Coupling the electrooxidation of organic compounds (EOO) with hydrogen evolution can be a sustainable way for green hydrogen production, and therefore it’s of great interest to the development of suitable electrocatalysts for efficient EOO. In this study, we present the successful solvothermal synthesis of a Pt-based electrocatalyst for an ethanol oxidation reaction (EOR), using a coral-like structure as substrate which was prepared by plasma electrolytic oxidation (PEO) on a metallic niobium. Chemical analysis revealed the predominance of SnO2 in the PEO structure, while Pt doping demonstrated selectivity on the surface of the electrocatalyst. Cyclic voltammograms indicate a high electrochemically active surface area (122.45 m² gPt−1), with an onset potential of 0.27 V vs. SHE. In-situ spectroelectrochemical analysis confirm the efficient ethanol electrooxidation with remarkable selectivity in C-C bond cleavage. The prepared electrocatalyst stands out as a promising contribution to advances in green hydrogen production by coupling EOR with hydrogen evolution.

PdSnW Ternary Alloy Nanoparticle with Excellent CO Anti‐Poisoning Activity for Boosting Alkaline Ethanol Oxidation Reaction

AbstractEfficient ethanol oxidation reaction (EOR) catalysts with anti‐poisoning ability and high selectivity are in high demand for the widespread application of direct ethanol fuel cells (DEFCs). Here, the PdSnW ternary alloy nanoparticles are synthesized by a facile solvothermal method and exhibit an enhanced EOR catalytic performance. CO stripping experiment, X‐ray photoelectron spectroscopy and in situ Fourier transform infrared are employed to study the correlation between catalyst structure and EOR catalytic performance. The oxyphilic Sn and W not only provide dangling O−H bond, accelerating the subsequent oxidation of adsorbed intermediate CO species, but also moderate the electron state of Pd, enhancing the adsorption of CH3CH2OH, thus resulting in the promotion of C−C bond cleavage and an increased C1 selectivity. As a consequence, PdSnW alloy nanoparticle catalyst exhibit a better stability and a higher mass activity than those of Pd/C, PdSn and PdW, respectively. This work not only offers novel insights to strategically design highly efficient electrocatalysts for ethanol oxidation, but also further clarifies the inherent structure‐activity relationship.

Toward Developing Superior Cu-Based Metal-Organic Framework-Derived Materials for Electrocatalytic Oxidation of Ethanol.

This project addresses the urgent need for efficient and cost-effective development of electrocatalysts for the ethanol oxidation reaction (EOR). This reaction offers promising renewable energy solutions but faces challenges due to the slow EOR kinetics, typically requiring costly noble metal catalysts. To overcome these limitations, this study focuses on developing CuZn-based EOR catalysts derived from metal-organic frameworks (MOFs), focusing on understanding the structure-performance relationship between pristine MOF-based electrocatalysts and their pyrolyzed counterparts. Herein, bimetallic MOF materials with varying Cu/Zn ratios were synthesized, followed by pyrolysis to produce carbonized counterparts while preserving the fundamental structure but with altered physicochemical properties. Comparative EOR studies revealed the superior performance of pyrolyzed MOFs, demonstrating that optimized Zn-loading is crucial over Cu-based framework for catalyst performance and durability. Overall, this work highlights the potential of MOF-derived Cu-based catalysts for renewable energy applications and provides insights into optimizing their performance through controlled synthesis and post-treatment strategies.

Ni-Pt-Pd ternary alloy nanoparticles supported on carboxyl-modified carbon nanotubes as highly efficient catalyst for methanol and ethanol electrooxidation

Pt-based catalysts are currently the most efficient anode catalysts in alcohol fuel cells. However, their widespread commercialization is hindered by their high cost. In this study, a straightforward method was employed to deposit Ni-Pt-Pd ternary alloy nanoparticles onto carboxyl-modified multi-walled carbon nanotubes (CNTs) and subsequently annealed the synthesized catalysts at different temperatures to adjust the surface composition and alloying degree. The Ni-Pt-Pd alloy exhibits a synergistic effect between Pt and Ni. The presence of Ni effectively modulates the d-band center of Pt, thereby enhancing the electrochemical performance of for alcohol oxidation. The synergistic effect of Pt-Pd alloy is harnessed to enhance both catalytic activity and stability of the catalyst for oxidation of methanol or ethanol. Density functional theory (DFT) calculations demonstrated that alloying Pt with Pd and Ni effectively reduced the Gibbs free energy during EOR and MOR reactions. The resulting catalysts, denoted as Ni6Pt6Pd6 NPs/CNTs-M2, exhibited exceptional catalytic oxidation performance for both ethanol and methanol. Specifically, their electrochemical mass activity for ethanol oxidation reaction (EOR) reached 2345 mA mg-1Pt+Pd, which was 15.5-fold and 2.56-fold higher than that of commercial Pt/C and Pd/C catalysts respectively. Moreover, their mass activity for methanol oxidation reaction (MOR) was measured at 2995 mA mg-1Pt+Pd, which was 8.2-fold and 5.3-fold higher than that of Pt/C and Pd/C catalysts respectively.

Rational development of semiconductor-based electrocatalyst and its electrochemical activity for ethanol oxidation as an assisted reaction for water splitting

Implementation of semiconductor-based nanocomposites for emerging technologies has been gaining exponential interest due to their unique physical, chemical, and electrochemical properties. Nonetheless, challenges still exist in developing active and stable materials to produce high-value-added electrocatalytic platforms for energy conversion applications. This work proposes the synthesis of a composite material comprising ZnO and Cu2O modified with SrSO4 by using the fast and versatile microwave heating process as feasible electrocatalysts for ethanol-assisted water electrolysis. The obtained composite was characterized by X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy (FESEM-EDS), Thermogravimetric Analysis (TGA), Fourier Transform Infrared (FTIR), and Raman spectroscopies. Electrochemical features were assessed by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The XRD results clearly show that composite material has reflections corresponding to the ZnO, Cu2O, and SrSO4, while the FESEM-EDS analysis reveals the presence of the desired chemical elements. The fabricated ZnO–SrSO4–Cu2O composite was electrochemically characterized to determine its potential as a catalyst for the ethanol oxidation reaction (EOR). The results unveil that the electroactivity of the composite is mainly attributed to the presence of Cu species and the synergistic effect of ZnO and SrSO4 compounds. In this way, this work proposes a novel via of fabricating active semiconductive electrocatalysts for the hybrid water electrolysis in the presence of the EOR. However, we believe this kind of material can be adopted in other applications such as sensors and energy storage devices.

Lattice-Expanded PdAg Spatial Nanodendrites as Catalysts for the Ethanol Oxidation Reaction

Lattice-Expanded PdAg Spatial Nanodendrites as Catalysts for the Ethanol Oxidation Reaction