Ethanol Electro-oxidation Reaction Research Articles

Evidence of surface restructuration on Pt–Rh/C and Pt–Rh–Ni/C nanoparticles applied to ethanol electrooxidation reaction

In this work, it is provided evidence of surface catalyst reconstruction on Pt–Rh/C and Pt–Rh–Ni/C alloys during the course of the ethanol oxidation reaction. Pt–Rh/C and Pt–Rh–Ni/C nanoparticles were synthesized by a chemical reduction method using sodium borohydride as a reducing agent. The characterization by X-ray diffraction analysis revealed distortions in the Pt lattice parameters for the Pt–Rh and Pt–Rh–Ni catalysts, due to the different atomic radii of the Rh and Ni substituents of the Pt atom in the structure of the alloys. Transmission electron microscopy analyses indicate that nanoparticles were distributed in island shapes, in clusters of various nanoparticles, with spherical shapes and particle sizes of 2–6 nm. It was observed an improvement in the electrocatalytic activity and stability on all materials studied due to the reconstruction of their surfaces during many cycling in the presence of ethanol. Additionally, in situ FTIR experiments evaluated before and after 100 voltammetric cycles in presence of ethanol suggest that the surface reconstruction affects the reaction by modifying the yield of the products, thus increasing the production of CO2 in detriment of acetic acid formation.

Synthesis and characterization the multifunctional nanostructures TixW1-xO2 (x = 0.5; 0.6; 0.7; 0.8) supports as robust non-carbon support for Pt nanoparticles for direct ethanol fuel cells

In the present study, various mesoporous TixW1-xO2 (x = 0.5; 0.6; 0.7; 0.8) supports were fabricated via a facile solvothermal approach and explored the effect of doping tungsten concentration on electrochemical properties of TixW1-xO2-supported Pt electrocatalysts toward ethanol electrochemical reaction. Interestingly, the incorporation of tungsten into TiO2 lattices with the doping tungsten amounts (20 and 30 at %) resulted in boosting both the surface area and electrical conductivity, however, a reverse trend was observed when increasing the doped tungsten content more than 40 at %. Additionally, the relatively well-distributed Pt nanoparticles with the small particle size (ca. 3 nm) anchored on supports were achieved using a microwave-assisted polyol route. Electrochemical results indicated that various TixW1-xO2-supported Pt catalysts exhibited the catalytic performance greater than that of the commercial carbon-supported Pt (E-TEK) catalyst for ethanol electro-oxidation reaction (EOR). For as-obtained electrocatalysts, the Ti0.7W0.3O2-supported Pt catalyst showed the highest mass activity (~260.23 mA/mgPt) and greatest If/Ib ratio (~1.34), which ~2.0-fold and ~1.57-time higher than that of carbon-supported Pt (E-TEK) catalyst (~130.62 mA/mgPt for mass activity and ~0.85 for If/Ib ratio, respectively). After 5000 cycling tests, the mass activity loss of TixW1-xO2-supported Pt catalysts was around twice lower than that of the commercial Pt/C (E-TEK) catalysts, suggesting that the TixW1-xO2-supported Pt catalysts exhibited the superior stability toward ethanol electrochemical oxidation. The outstanding electrochemical activity and stability of TixW1-xO2-supported Pt electrocatalysts were owing to the synergetic effect between Pt nanocatalyst and non-carbon TixW1-xO2 supports as well as superior natural durability of TiO2-based materials.

Ethanol electro‒oxidation and spectroelectrochemical analysis of highly active sub

In this work, PdFe2O3 bimetallic materials containing oxygen vacancies (Ov, from 10 to 75%) and two bimetallic nanoparticles based on noble metals (PdAu and PdPt) were obtained and evaluated for the ethanol electro‒oxidation reaction (EOR) in alkaline medium. For this purpose, bimetallic nanoparticles were synthesized keeping similar crystallite sizes (~6 nm), particle sizes (~6 nm), mass compositions (18 ± 4% co‒metal) and metallic loadings (18.3 ± 5.1%). PdAu/C, PdPt/C and the most active PdFe2O3/C material (75% of Ov) displayed an improved onset potential (Eonset) during the oxidation of 1.5 M ethanol in 0.3 M KOH in comparison with a monometallic Pd/C material, finding the trend: PdAu/C (−0.56 V vs. NHE) > PdPt/C (−0.55 V) > PdFe2O3/C (−0.51 V) > Pd/C (−0.50 V). In addition, these bimetallic materials presented an increase in the current density; being PdPt/C and PdFe2O3/C the most active materials for EOR. A spectroelectrochemical analysis was performed by coupling a μRaman spectroscope with an electrochemical cell. This analysis allowed to conclude that the improvement of the Eonset is related to changes in chemisorption energies as was suggested by Raman shifts found for the C1‒M (metal) bond, while the high activity of PdPt/C can be attributed to a higher adsorption of ethanol molecules. Additionally, it was found that the activity of PdFe2O3/C is associated with an energy decrease to form the C1‒M bond, which could be promoted by the abundance of oxygen vacancies.

Effect of tin deposition over electrogenerated random defects on Pt(111) surfaces onto ethanol electrooxidation: Electrochemical and FTIR studies

In the present study, random superficial defects of the {110}-type were electrogenerated on an initially well-ordered Pt(111) single crystal electrode, by cycling the potential in the range from 0.05 to 1.30 V by 32 times in perchloric acid solution and in a scan rate of 0.05 V s−1, named as Pt(111)-32. After partial disordering of the electrode surface, it was modified by deposition of tin submonolayers in three different coverage degrees of Sn, namely, ѲSnDefects= 0.34, 0.54 and 1.0. The Sn is preferentially deposited on the {110}-type defects generated previously. The effect of tin over the electrocatalytic activity for the ethanol electrooxidation reaction (EOR) and CO oxidation was investigated by using cyclic voltammetry, while the mechanism of the alcohol oxidation on the unmodified and Sn-modified electrodes was investigated by using in situ Fourier Transform Infrared (FTIR) spectroscopy. The lower Sn coverage degree on defect sites (ѲSnDefects= 0.34) showed, in the first voltammetric cycle, very good performance for EOR, having a peak current at 0.58V twice the one observed for the unmodified Pt(111)-32 electrode. However, the situation changed in the second voltammetric cycle, where on the full Sn covered defect sites electrode (ѲSnDefects= 1) a better electrocatalytic response was observed with more tolerance to the strongly adsorbed blocking intermediate species at low potentials. Additionally, it was found that this behavior should be in part associated with the ability of this electrode decorated with Sn to oxidize CO at a lower potential than those observed for other surfaces. The production of CO2 and acetic acid is enhanced as the Sn coverage degree also increases, as shown by FTIR, however, the later product is the majority product of this reaction for all the investigated electrodes. Thus, the main effect of Sn is reflected in the increased production of acetic acid.

Enhanced Electrocatalytic Activities toward the Ethanol Oxidation of Nanoporous Gold Prepared via Solid-Phase Reaction

The rational design of highly active electrocatalysts for ethanol electrooxidation reaction (EOR) is important for future commercial application of efficient direct ethanol fuel cells. Herein, we describe application of a solid-phase reaction for the creation of a well-defined, high-efficiency, nanoporous gold (NPG) electrocatalyst for EOR. The evaluation of the feature size and physical properties of the NPG electrocatalysts was undertaken using field-emission scanning electron microscopy and high-resolution transmission electron microscopy. Additionally, the catalytic performance of the prepared NPG electrocatalysts was determined using cyclic voltammetry (CV) and chronoamperometry (CA), with results indicating that their enhanced electrocatalytic activities and long-term durability were highly dependent upon morphology. The created NPG exhibited a mass activity of 308 mA mgAu−1 toward EOR in alkaline media, which is much higher than those of nanostructured Au catalysts. In particular, 800-cycle CV and ...

CuO-grafen Nanokompozitlerinde Etanol Elektrooksidasyonu

Bu çalışmada Au elektrot yüzeyinde CuO-grafen (CuO/G) nanokompozitlerinin tek aşamalı elektrokimyasal sentezi gerçekleştirilmiştir. CuO/G yapılarının analitik karakterizasyonu için XRD ve EDS teknikleri kullanılmıştır. Morfolojik karakterizasyonu ise SEM kullanılarak yapılmıştır. CuO/G kompozitlerinin etanol elektro-oksidasyon reaksiyonunda elektrokatalizör olarak kullanımı incelenmiş ve dönüşümlü voltametri tekniği kullanılarak katalitik özellikleri araştırılmıştır. Etanol oksidasyonu için en yüksek akım yoğunluğu CuO/G kompozitinde elde edilmiştir. Sentezlenen nanokompozit filmin yakıt hücrelerinde elektrot malzemesi olarak kullanılabileceği belirlenmiştir.

Insights into the Pt/Rh(1 1 1) interface for direct ethanol fuel cells

Finding a highly efficient electro-catalyst for ethanol oxidation is the central issue in the use of direct ethanol fuel cells. Recently, fabricating interfacial sites between two phases has been reported as an effective approach to boost the heterogeneous catalytic activity. In this work, a comprehensive understanding of how the Pt/Rh(1 1 1) interface promotes ethanol electro-oxidation for direct ethanol fuel cells at atomic levels is gained by employing density functional theory (DFT) calculations. It is found that the Pt/Rh(1 1 1) interface including (1 1 1) × (1 1 0) and (1 1 1) × (1 0 0) could effectively convert ethanol to CH3CO* and the Rh(1 1 1) surface could activate water at low potentials (<0.5 V) by forming several ordered surface oxygen-containing species adlayers. Moreover, OH* is identified to be an oxidant and CH3CO* oxidation rate on (1 1 1) × (1 1 0) is faster than that on (1 1 1) × (1 0 0). It is therefore suggested that the (1 1 1) × (1 1 0) interface over Pt/Rh(1 1 1) is the active site for catalyzing ethanol electro-oxidation into CH3COOH. These results highlight the significance of metal/metal interfaces and help screen such interfacial catalysts in the design of highly active catalysts for ethanol electro-oxidation reactions.

Wire-like Pt on mesoporous Ti0.7W0.3O2 Nanomaterial with Compelling Electro-Activity for Effective Alcohol Electro-Oxidation

Finding out robust active and sustainable catalyst towards alcohol electro-oxidation reaction is major challenges for large-scale commercialization of direct alcohol fuel cells. Herein, a robust Pt nanowires (NWs)/Ti0.7W0.3O2 electrocatalyst, as the coherency of using non-carbon catalyst support and controlling the morphology and structure of the Pt nanocatalyst, was fabricated via an effortless chemical reduction reaction approach at room temperature without using surfactant/stabilizers or template to assemble an anodic electrocatalyst towards methanol electro-oxidation reaction (MOR) and ethanol electro-oxidation reaction (EOR). These observational results demonstrated that the Pt NWs/Ti0.7W0.3O2 electrocatalyst is an intriguing anodic electrocatalyst, which can alter the state-of-the-art Pt NPs/C catalyst. Compared with the conventional Pt NPs/C electrocatalyst, the Pt NWs/Ti0.7W0.3O2 electrocatalyst exhibited the lower onset potential (~0.1 V for MOR and ~0.2 for EOR), higher mass activity (~355.29 mA/mgPt for MOR and ~325.01 mA/mgPt for EOR) and much greater durability. The outperformance of the Pt NWs/Ti0.7W0.3O2 electrocatalyst is ascribable to the merits of the anisotropic one-dimensional Pt nanostructure and the mesoporous Ti0.7W0.3O2 support along with the synergistic effects between the Ti0.7W0.3O2 support and the Pt nanocatalyst. Furthermore, this approach may provide a promising catalytic platform for fuel cell technology and a variety of applications.

Pd, Pd–Ni and Pd–Ni–Fe nanoparticles anchored on MnO2/Vulcan as efficient ethanol electro-oxidation anode catalysts

Pd–Ni–Fe nanoparticles supported on MnO2/Vulcan XC-72 R (carbon black powder) as the electrocatalyst for the anodic oxidation of ethanol in a direct ethanol alkaline fuel cell (DEAFC) has been conducted. Electrocatalyst structures and morphologies are investigated by XRD, FE-SEM, EDX and elemental mapping techniques and subsequently electrochemical performance of electrocatalysts for ethanol oxidation reaction (EOR) are studied by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). Pd/MnO2/Vulcan, Pd–Ni/MnO2/Vulcan and Pd–Ni–Fe/MnO2/Vulcan efficiently advanced ethanol electro-oxidation reaction under alkaline conditions. Pd/MnO2/Vulcan revealed best potential window and low charge transfer resistance (Rct) for EOR. Pd–Ni/MnO2/Vulcan and Pd–Ni–Fe/MnO2/Vulcan electrocatalysts have a good anti CO-poisoning capability. Pd–Ni–Fe/MnO2/Vulcan has significantly high current density, excellent catalyst durability and cyclic stability for ethanol oxidation which encourage researchers for application of such exceptional materials as anode electrocatalysts in DEFC.

Recent developments in nickel based electrocatalysts for ethanol electrooxidation

A survey is done to gain a general idea in the development of various nickel based anode electrocatalysts for ethanol electrooxidation reaction. Platinum and other noble metal electrocatalysts are very well known but their cost and scarcity is a major issue hampering its use on a commercial level. Apart from cost, the poisoning of noble metal electrocatalysts due to CO is also another issue. These issues can be tackled by partially or fully replacing the noble metal electrocatalysts by non-noble metal electrocatalysts. The use of electrocatalytically active non-noble metal like nickel provides an excellent alternative. Hence, major thrust is laid upon the use of nickel in the form of either as a single or a complementary element in the electrocatalysts containing two (binary), three (ternary), four (quaternary) or more noble and/or non-noble metals to improve the electrocatalytic activity for ethanol electrooxidation reaction. The quality of an electrocatalyst is decided on a number of factors. Onset potential and current density are the two main parameters representing the activity of electrocatalysts. Complete oxidation of ethanol to give CO2 is a major requirement to extract maximum current. Literature survey shows that support, synthesis approaches and elemental compositions greatly contributes to enhance the electrocatalytic performance of nickel based electrocatalysts towards ethanol electrooxidation reaction.

Ni(OH)2 Decorated Pt-Cu Octahedra for Ethanol Electrooxidation Reaction.

Here we report the synthesis of 9 nm Ni(OH)2 decorated Pt-Cu octahedra (Ni(OH)2-PtCu) in one-pot synthesis for ethanol oxidation reaction (EOR) electrocatalysis in acidic electrolyte. To prepare Ni(OH)2-PtCu octahedra, CO gas was directly introduced in a reaction process as selective capping agents on the PtCu(111) facet. Ni(OH)2 was naturally deposited on the Pt-Cu octahedra during the synthesis. Carbon supported Ni(OH)2-PtCu (Ni(OH)2-PtCu/C) as an EOR catalyst showed enhanced CO tolerance due to the existence of oxophilic Ni(OH)2 on the surface of Pt-Cu, facilitating water dissolution to produce OH adsorption and to promote complete CO oxidation to CO2. In addition, Pt-Cu alloy composition also showed improvement of CO tolerance because of modified d-band structure of the Pt atoms, thereby weakening the binding strength of CO on the catalysts. Therefore, the Ni(OH)2-PtCu/C showed enhanced EOR activity and durability compared to the Pt-Cu octahedra and commercial Pt/C counterparts.

Tungsten-doped titanium-dioxide-supported low-Pt-loading electrocatalysts for the oxidation reaction of ethanol in acidic fuel cells

High cost and poor durability of Pt-based electrocatalysts are the main challenges for future commercialization of direct ethanol fuel cells (DEFCs). In the present work, a stable and effective Pt/Ti 0.8 W 0.2 O 2 electrocatalyst toward ethanol electrooxidation reactions (EORs) was prepared by utilizing the attributes of noncarbon catalyst supports and low Pt loading. The 18.5 wt % Pt/Ti 0.8 W 0.2 O 2 electrocatalyst was successfully fabricated through a simple and rapid microwave-assisted polyol route (ethylene glycol was used as a reducing agent). In comparison with a conventional 20 wt % Pt/C electrocatalyst, the as-prepared 18.5 wt % Pt/Ti 0.8 W 0.2 O 2 electrocatalyst resulted in much lower onset potential, higher I f / I b value, and superior stability toward EOR, which can be ascribed to the synergistic effect between Pt nanocatalyst and the Ti 0.8 W 0.2 O 2 catalyst support. Therefore, these findings imply that 18.5 wt % Pt/Ti 0.8 W 0.2 O 2 is a promising anodic electrocatalyst and possesses the ability to replace Pt/C electrocatalysts in the future.

Facile synthesis of AuPd nanowires anchored on the hybrid of layered double hydroxide and carbon black for enhancing catalytic performance towards ethanol electro-oxidation

Improving the catalytic performance of ethanol electro-oxidation reaction (EOR) is crucial for accelerating the commercialization of direct ethanol fuel cells (DEFCs). In this work, AuPd nanowires (NWs) anchored on the hybrid of layered double hydroxides and carbon black (CB) was prepared by a facile procedure for anode electrocatalyst of ethanol electro-oxidation reaction (EOR). For comparison, unloaded AuPd NWs and AuPd nanopaticles (NPs) supported on LDH-CB were also prepared. These catalysts were characterized via X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The performance of these catalysts was evaluated by the reactions of ethanol in alkaline media by cyclic voltammetry, chronoamperometric measurements and electrochemical impedance spectroscopy. It was found that the as-prepared AuPd NWs/LDH-CB demonstrated higher activity and stability than those of unloaded AuPd NWs, commercial Pd/C and AuPd NPs/LDH-CB attributed to the AuPd nanowires with more active sites, electronic structure of Pd modified by alloyed with Au and interacted with LDH-CB as well as the electron transfer ability facilitated by CB.

Effect of the Random Defects Generated on the Surface of Pt(111) on the Electro-oxidation of Ethanol: An Electrochemical Study.

In the present work, the Pt(111) surface was disordered by controlling the density of {110}- and {100}-type defects. The cyclic voltammogram (CV) of a disordered surface in acid media consists of three contributions within the hydrogen adsorption/desorption region: one from the well-ordered Pt(111) symmetry and the other two transformed from the {111}-symmetry with contributions of {110}- and {100}-type surface defects. The ethanol oxidation reaction (EOR) was studied on these disordered surfaces. Electrochemical studies were performed in 0.1 M HClO4 +0.1 M ethanol using cyclic voltammetry and chronoamperometry. Changes in current densities associated to the specific potentials at which each oxidation peak appears suggest that different surface domains of disordered platinum oxidize ethanol independently. Additionally, as the surface-defect density increases, the EOR is catalysed better. This tendency is directly observed from the CV parameters because the onset and peak potentials are shifted to less positive values and accompanied by increases in the oxidation-peak current on disordered surfaces. Similarly, the CO oxidation striping confirmed this same tendency. Chronoamperometric experiments showed two opposite behaviors at short oxidation times (0.1 s). The EOR was quickly catalyzed on the most disordered surface, Pt(111)-16, and was then rapidly deactivated. These results provide fundamental information on the EOR, which contributes to the atomic-level understanding of real catalysts.

Direct conversion of inorganic complexes to platinum/thin oxide nanoparticles decorated on MOF-derived chromium oxide/nanoporous carbon composite as an efficient electrocatalyst for ethanol oxidation reaction

In this work, we present the design and fabrication of a novel nanocomposite based on noble metal and metal oxide nanoparticles dispersed on highly porous carbon obtained via the pyrolysis of an inorganic complex and metal-organic frameworks. This nanocomposite is prepared by a two-step procedure: first, the composite support of nanoporous carbon (NPC) is obtained by the direct carbonization of the Cr-benzene dicarboxylic ligand (BDC) MOF in an Argon atmosphere at 500 °C (Cr2O3-NPC). A mixture containing Cr2O3-NPC and [PtCl(SnCl3)(SMe2)2] is then prepared, and underflow of Argon is heated to 380 °C. Finally, Pt-SnO2 nanoparticles are loaded on the Cr2O3-NPC support, and the obtained nanocomposite was denoted as Pt-SnO2/Cr2O3-NPC. The morphology and crystalline structure of the prepared nanocomposites were characterized using XRD, SEM, EDX, FT-IR, and XPS. In addition, the prepared nanocomposite was examined as a novel electrocatalyst for the ethanol electro-oxidation reaction (EOR). The obtained results demonstrated that, compared with Pt/Cr2O3-NPC, Pt-SnO2/Cr2O3-NPC showed higher electrocatalytic activity, lower onset potential, and a higher level of poisoning tolerance toward of ethanol oxidation in acidic media. The overall results corroborate the predominant role of SnO2 as an excellent catalytic-enhancing agent thorough facilitating the charge transfer process and increasing the CO poisoning oxidation by the spillover of OHads to the Pt surface. Thus, the prepared Pt-SnO2/Cr2O3-NPC catalyst could be considered a promising anode catalyst for direct ethanol fuel cells.

Enhancing Activity of Pd-Based/rGO Catalysts by Al-Si-Na Addition in Ethanol Electrooxidation in Alkaline Medium

The article presents modified Pd-based catalysts supported on reduced graphene oxide (rGO), used in the electrooxidation reaction of ethanol in alkaline medium. When NaBH4 reducing agent was used, the random presence of Na was found out. According to this result, Na was used as a promoter of Pd-based catalyst. Consequently, the Al-Si-Na addition not only assisted active phase Pd nanoparticles to disperse homogenously on graphene surport, but also contributed to increase catalytic activity in the reaction. This value, 16138 mA·mg−1Pd, is about 1.5 times higer than that of the catalyst modified by Al-Si. Moreover, the stability of the catalyst is enhanced more. The electrochemical stability of PASGN.N catalyst was relatively good: after 500 scanning cycles, the current density diminished 32% compared with the highest peak current density of the 15th cycle, which was chosen as a reference. These significant improvement results in electrooxidation of ethanol have opened up the high potential application of these catalysts in direct-ethanol fuel cell.

Catalytic oxidation of ethanol by a nanostructured Ni-Co/RGO composite: Electrochemical construction and investigation

Electrocatalysis of ethanol was performed by a nanocomposite which was fabricated by carbon paste electrode modified with reduced graphene oxide supported bimetallic NiCo nanoparticles (Ni-Co/RGO/CPE). It was characterized by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction spectroscopy and cyclic voltammetry. The cyclic voltammetric studies in different conditions showed redox activity of the Ni nanoparticles in the form of Ni(OH)2/NiOOH couple. This redox activity was improved by the presence of Co nanoparticles and reduced graphene oxide nanosheets. The oxidation of ethanol was investigated in alkaline media at the Ni-Co/RGO/CPE. The anodic peak potential of ethanol oxidation was decreased and its current was greatly enhanced at the surface of the suggested electrocatalyst. Also, the chronoamperometry technique was employed for obtaining the catalytic rate constant for the electro-oxidation reaction of ethanol and a value of 2150cm3mol−1s−1 was obtained.

An environmentally friendly one-pot synthesis method by the ultrasound assistance for the decoration of ultrasmall Pd-Ag NPs on graphene as high active anode catalyst towards ethanol oxidation.

An environmentally friendly one-pot synthesis approach for the decoration of Pd-Ag nanoparticles with the ultrasmall size on graphene (Pd-Ag/G) by the assistance of ultrasound is proposed in this paper. This method offers exceptional advantages over other approaches such as environmentally friendly synthesis, being low temperature, reductant, surfactant free, simple, fast and one-pot synthesis. In this work, silver formate is added to the graphene suspension at 25 °C. Then, PdCl2 is added to the suspension under stirring to fabricate Pd-Ag/G. The uniform dispersity of nanoparticles with an average size of about 2-3 nm is well confirmed by transmission electron microscopy micrographs. The resultant catalyst is applied as anode electrocatalyst towards electrooxidation reaction of ethanol. The Pd-Ag/G catalyst displays exceptional catalytic activity and durability towards electro-oxidation of ethanol. According to the obtained results, it be concluded that the combination of Ag and Pd, ultrasmall and uniform distribution of Pd-Ag nanoparticles led to the improvement of electrocatalytic activity of the Pd-Ag/G catalyst.

A mathematical model for direct ethanol fuel cells based on detailed ethanol electro-oxidation kinetics

This paper presents an isothermal, single-phase model for direct ethanol fuel cells. The ethanol electro-oxidation reaction is described using a detailed kinetic model that is able to predict anode polarization and product selectivity data. The anode kinetic model is coupled to a one-dimensional (1D) description for mass and charge transport across the membrane electrode assembly, which accounts for the mixed potential induced in the cathode catalyst layer by the crossover of ethanol and acetaldehyde. A simple 1D advection model is used to describe the spatial variation of the concentrations of the different species as well as the output and parasitic current densities along the flow channels. The proposed 1D + 1D model includes two adjustable parameters that are fitted by a genetic algorithm in order to reproduce previous experimental data. The calibrated model is then used to investigate the consumption of ethanol and the production, accumulation and consumption of acetaldehyde along the flow channels, which yields the product selectivity at different channel cross-sections. A parametric study is also presented for varying ethanol feed concentrations and flow rates. The results obtained under ethanol starvation conditions highlight the role of acetaldehyde as main free intermediate, which is first produced and later consumed once ethanol is fully depleted. The detailed kinetic description of the ethanol oxidation reaction enables the computation of the four efficiencies (i.e., theoretical, voltage, faradaic, end energy utilization) that characterize the operation of direct ethanol fuel cells, thus allowing to present overall fuel efficiency vs. cell current density curves for the first time.

A one-pot route for the synthesis of Au@Pd/PMo12/rGO as a dual functional electrocatalyst for ethanol electro-oxidation and hydrogen evolution reaction.

An in situ one-pot synthetic route for the synthesis of a Au@Pd/PMo12/reduced graphene oxide (rGO) nanocomposite is presented, where the Keggin-type polyoxometalate phosphomolybdic acid (PMo12) is used as both reducing and stabilizing agent. High-angle annular dark-field scanning transmission electron microscopy (HAADT-STEM), transmission electron microscopy (TEM), and X-ray diffraction analysis were applied to fully characterize the core–shell structure of Au@Pd/PMo12 on the rGO matrix. Electrochemical studies showed how this nanocomposite acts as a dual electrocatalyst for the ethanol electro-oxidation reaction (EOR) and the hydrogen evolution reaction (HER). For the EOR, the Au@Pd/PMo12/rGO electrocatalyst offers a low onset potential of −0.77 V vs. Ag/AgCl and a high peak current density of 41 mA cm−2 in alkaline medium. This feature is discussed via detailed cyclic voltammetry (CV) studies illustrating how the superior performance of the synthetic nanocomposite could be attributed to the synergistic effect of Au, Pd, PMo12 and rGO. Moreover, it has been confirmed that the proposed electrocatalyst exhibits low overpotentials for 10 mA cm−2 current density (η10) in different pH media. The values of η10 were −109, 300 and 250 mV vs. RHE in acidic, basic and neutral media, respectively. Also, the ability of the electrocatalyst to provide high HER current density and its remarkable stability have been confirmed.