Direct Ethanol Research Articles

Performance of BiCu2O modified Pd/C as an anode electrocatalyst for direct ethanol fuel cell system

BiCu2O Modified Pd/C nanocatalyst was synthesised via an eco-friendly method for fuel cell application. The obtained nanomaterials' structural composition, and electrochemical properties were investigated using chemical and physical techniques such as impedance spectroscopy (EIS), X-ray diffraction (XRD), high resolution-scanning electron microscopy (HR-SEM), and cyclic voltammetry (CV). The preparation of the BiCu2O Modified Pd/C catalyst was successfully verified by microscopic techniques, as shown by the presence of mixed nanostructures, Pd and BiCu2O coexisting. EIS measurements confirmed a smaller electron charge-transfer (160 Ω) for the prepared Pd/C-BiCu2O nanocatalyst. From the Pd oxide peaks, the electrochemical active surface area (EASA) values for Pd/C-BiCu2O and Pd/C were estimated to be 432.1 cm2 mg−1 and 79.2 cm2 mg−1, respectively. The resulting BiCu2O Modified Pd/C nanocatalyst showed increased ethanol oxidation activity (If/Ib=1.1) and was more resistant to poisoning by advanced oxidation species. Under passive conditions at 1 M ethanol in 1 M KOH, improved cell performance (cell output = 120 mW) with a high density of current (105 mAcm−2) and power density (25.7 mWcm−2) relative to the commercial Pd/C were obtained. The study opens and forges novel possibilities in the search for new carbon co-catalysts for direct ethanol fuel cell (DEFC) application because of the simplified green processing and the cost of the precursor and the Pd-based catalyst produced. The work involves using difficult waste streams produced by various agro-industrial operations to create high surface material for use in producing commodities with added value. This work will also help address climate action, clean and affordable energy crisis.

Facile Synthesis of Nitrogen Doped Porous Carbon Supported Platinum Catalyst and Improvement of Electrocatalytic Ethanol Performance

Direct ethanol fuel cells (DEFCs) have become an alternative to traditional fossil fuels because of their low emissions, fast start-up and high energy density. Platinum (Pt)-based catalysts are the most effective catalysts for DEFCs, but their high cost and poor electrocatalytic performance hinder their practical application. Therefore, there is an urgent need to design Pt-based catalysts with low platinum content, high electrochemical activity and stability. Herein, nitrogen-doped porous carbon-loaded Pt catalysts (Pt@Co-CN) were prepared by in situ polymerization and high-temperature calcination using the metal-organic framework materials (MOFs) ZIF-8@ZIF-67 as the carriers. The effects of the addition of pyrrole monomer on the morphology and electrocatalytic properties of the samples were investigated. The sample with the complete coating layer and uniformly dispersed Pt nanoparticles (Pt@Co-CN) could be obtained by adding an appropriate amount of pyrrole monomer. The results of the electrochemical tests showed that the electrochemical activity of Pt@Co-CN catalytic ethanol is superior to that of commercial catalysts and samples with insufficient or excessive addition of pyrrole monomers. The content of this study provides a new method for the electrocatalyst of DEFCs.

Development of LC-MS/MS Method of Measurement of Direct Ethanol Biomarkers Ethyl Glucuronid and Ethyl Sulfate in Urine and Serum Matriches in Detection and Tracking of Alcohol Use

Development of LC-MS/MS Method of Measurement of Direct Ethanol Biomarkers Ethyl Glucuronid and Ethyl Sulfate in Urine and Serum Matriches in Detection and Tracking of Alcohol Use

Effective ethanol-to-CO2 electrocatalysis at iridium-bismuth oxide featuring the impressive negative shifting of the working potential

Since low overpotential for the anodic ethanol oxidation reaction (EOR) can favor the higher output voltage and power of direct ethanol fuel cells (DEFCs), it is critical to design new EOR catalysts with efficient ethanol-to-CO2 activity at low applied potentials. Thereby, carbon-supported Ir-Bi2O3 (Ir-Bi2O3/C) catalysts with highly dispersive bismuth oxide on the iridium surface are designed and prepared, which can merit splitting the ethanol C–C bond and promoting the oxidation of C1 intermediates at the bifunctional interfaces. The as-obtained Ir-Bi2O3/C catalysts show superior EOR mass activity of up to ca. 2250 mA mg−1Ir. Moreover, they exhibit the record lowest onset oxidation potentials (0.17–0.22 V vs. RHE) and the peak potential (ca. 0.58 V vs. RHE), being 130–300 mV lower than the previous landmark noble metallic catalysts. Furthermore, an apparent C1 pathway faraday efficiency (FEC1) of 28% ± 5.9% at 0.5 V vs. RHE can be obtained at Ir-Bi2O3/C. This work might provide new insights into the new anodic EOR catalysts for increasing the power of DEFCs.

Parameter estimation for empirical and semi-empirical models in a direct ethanol fuel cell

Experimental data from a Direct Ethanol Fuel Cell (DEFC) provides a general perspective about its performance; nevertheless, it does not provide information about the cell’s physical characteristics nor information to improve its performance. On the other hand, numerical simulation can be used to test the cell’s design and boost its performance but requires a set of physical parameters. In this proposal, we introduce a novel modification to an empirical model for a Direct Methanol Fuel Cell to make it suitable for DEFC simulations at different temperatures by a new semi-empirical mathematical model. In addition, we introduce temperature-depending parametric forms of several terms to reduce the number of possible parameters to estimate from the DEFC. Then, we combined the models with an estimation of distribution algorithm to find the numerical simulation that best reproduces the experimental polarization curve. The method is validated by estimating the parameters to reproduce the experimental data at different temperatures reported in the literature, and with data obtained in an in-house open-cathode DEFC, recorded at a scan rate of 10 mVs−1, using as fuel CH3CH2OH 1 M at 25 °C and 60 °C. From the estimation results at temperature set T1→=(T1a,T1c)∘C, the same parameters are used for a simulation at T2→=(T2a,T2c)∘C, demonstrating that it reproduces the two experimental polarization curves. Hence, the models and methods presented here can be used to reduce physical experimentation and to test different designs and operation settings.

Confinement Effects of Hollow Structured Pt-Rh Electrocatalysts toward Complete Ethanol Electrooxidation.

In the anodic ethanol oxidation reaction (EOR) for direct ethanol fuel cells, the coverage of hydroxide (OHads) is a major adsorbent competing with C-C bond cleavage, which is necessary for complete ethanol oxidation (C1-pathway) and durability. Beyond utilizing a less-alkaline electrolyte that causes ohmic losses, an alternative strategy to optimize OHads coverage is to intentionally exploit local pH changes near the electrocatalyst surface that are governed by a combination of released H+ during EOR and OH- mass transport from the bulk solution. Here, we manipulate the local pH swing by fine-tuning the electrode porosity with Pt1-xRhx hollow sphere electrocatalysts based on particle size (250 and 350 nm) and mass loading. With the smaller size of 250 nm, Pt0.5Rh0.5 (∼50 μg cm-2) shows a high activity of 1629 A gPtRh-1 (2488 A gPt-1) in a 0.5 M KOH-containing electrolyte, which is ∼50% higher than the most active binary catalysts to date. Moreover, a higher C1-pathway Faradaic efficiency (FE) of 38.3% and 80% longer durability are achieved with a 2-fold increase in mass loading. In the more porous electrodes, a local acidic environment created by hindered OH- mass transport better optimizes OHads coverage, providing more active sites for the desired C1-pathway and a continuous EOR.

Cryogels from Pt/γ-Fe2O3 and Pd/γ-Fe2O3 NPs as Promising Electrocatalysts for Ethanol Oxidation Reaction

Cryogels from noble metal NPs have proven to be highly efficient catalysts due to their high specific surface area which increases the mass transfer channels and catalytic active sites. By using metal oxides as co-catalysts, the costs of the material can be significantly reduced, while the catalytic activity can remain the same or even improve due to synergetic effects. In this work, we synthesize different cryogel thin films supported on modified ITO substrates from Pt, Pd nanoparticles (NPs), and mixtures of these noble metals with γ-Fe2O3 NPs in a very low concentration (1 wt% of the noble metal). Structural and elemental analysis of the samples are performed, along with the measurement and analysis of their catalytic activity. The electrocatalytic activity of the cryogels towards ethanol oxidation reaction (EOR) in alkaline media was evaluated by means of cyclic voltammetry. By mixing γ-Fe2O3 NPs with Pt or Pd NPs in the cryogel structure, we observe increased tolerance against poisonous surface intermediates produced during the EOR. Moreover, we observe an increase in the catalytic activity towards EOR in the case of the 1 wt% Pd/γ-Fe2O3 cryogel, making them promising materials for the development of direct ethanol fuel cells.

Nano‐Nickel Doped Carbon Xerogel: Synthesis, Characterization and Catalytic Performance towards Ethanol Fuel Electro‐oxidation

AbstractIn this work, the synergism between the nano nickel particles and its carbon xerogel support, CX, together with their graphite substrate, G, leads to an efficient Nickel/CX/G electrode for electrocatalysis of ethanol oxidation reaction, EOR. The preparation conditions are optimized. The optimum electrode is made of 6 % weight of Ni doped in CX matrix and drop‐casted on a graphite surface, Ni‐6/CX/G. The catalyst structure and morphology are investigated using XRD, SEM, TEM and FTIR techniques. The electrochemical activity towards EOR is tested in 1 M NaOH+1 M Ethanol solutions by cyclic voltammetry combined with a rotating ring disk electrode. The optimum electrode shows an oxidation peak current density value of 5925 and considerable stability. This electrode may serve as a good candidate for the anode in the Direct Alkaline Ethanol Fuel Cell, DAEFC.

Conductive core/shell polymer nanofibres as anode materials for direct ethanol fuel cells

A conductive polymer-supported electrocatalyst in the form of fibrous mat has been developed that can be employed as a polymer-based electrode for direct ethanol fuel cells (DEFCs) with promoting effects to the state-of-the art Pd based catalysts. A series of conductive polyaniline (PANI)-containing polymer fibres-supported Pd electrocatalytic electrodes were successfully prepared and tested for the ethanol electro-oxidation reaction (EOR) in alkaline medium. The polymer support was a robust fibrous mat, where the fibres possessed a core-shell configuration. The core part was produced via electrospinning using a mixture of polyacrylonitrile (PAN) and 1-butyl-3-methylimidazolium chloride [BMIm]Cl ionic liquid (IL). The shell was a PANI layer deposited via the chemical polymerisation of aniline monomer. Pd was then electrodeposited on the fibres and the catalysts were tested for the EOR via cyclic voltammetry (CV) in a half-cell configuration and in a temperature range between 25 and 60 °C. The activity of the catalysts tested was measured in terms of activation energy and forward peak current density in the CV and compared to that of glassy carbon (GC)-supported Pd/PANI/PAN/IL fibrous catalysts. The polymer fibre-catalyst samples showed a higher active surface area and significantly lower activation energy than the GC-based ones. Even though the GC-supported catalysts showed a higher activity in terms of current, the Pd/(PAN/IL)-core/PANI-shell fibrous mats were active as well and, in some cases, demonstrated a promoting effect of PANI on Pd for EOR and a much better stability and robustness compared to the former. Furthermore, a series of promoting metals were investigated for these mats, such as Ag, Bi and Cu, with Ag and Bi demonstrating promoting effects compared to monometallic Pd/(PAN/IL)-core/PANI-shell mats in terms of both activation energy and peak current density. This work demonstrates a promising strategy in the arena of development of polymeric mats as anode electrodes for DEFCs, exploiting the benefits of PANI in terms of ease of synthesis, catalyst poisoning prevention, cost and promoting effects.

Simple Synthesis of AuPd Aerogel as a Self-Supporting Electrocatalysts with Excellent Performance

Direct ethanol fuel cell (DEFC) has the advantages of low pollution emissions, easy to carry, and high energy density. However, the development of fuel cells is limited due to the low catalytic activity and poor stability of electrode catalyst materials. Precious metal aerogels not only have three-dimensional self-supporting network structures but also have excellent properties of precious metals, which have very good catalytic efficiency for ethanol. In this study, bimetallic aerogels with varying Au/Pd ratios were prepared, and their impact on the electrocatalytic performance of ethanol was investigated.

Dealloying fabrication of nickel Oxyhydroxide/Oxide-based composites boosting ethanol electrooxidation

Developing inexpensive and highly active ethanol electrooxidation catalysts with long service lives for direct ethanol fuel cells is an urgent task. Herein, prismatic NiO(OH)/CeO@Ce(OH)3 and nanoporous NiCe–O composites are fabricated on the surfaces of Ce-containing alloy ribbons via one-step dealloying, demonstrating excellent catalytic performance for the ethanol oxidation reaction (EOR). Particularly, the Ti50Ce10Ni40 ribbon dealloyed for 2 h at a hydrothermal temperature of 140 °C exhibits a high current density of 229.4 mA cm−2 (1.6 V vs. the reversible hydrogen electrode) and maintains outstanding performance for 10 h without apparent deterioration, outperforming most state-of-the-art non-noble catalysts. This phenomenon is associated with the formation of a prismatic NiO(OH)/CeO@Ce(OH)3 array structure on the alloy ribbon surface with abundant active sites and defects, enhancing the catalyst activity and stability. This study may provide new opportunities for designing and fabricating inexpensive and robust catalysts with excellent performance and a wide range of practical applications.

Design optimization of 3D printed flow path plates in high-performance bioethanol fuel cells

PurposeEffective performance of a direct ethanol fuel cell (FC) stack depends on the satisfactory operation of its individual cells where it is always challenging to manage the temperature gradient, water flow and distribution of reactants. In that, the design of the bipolar fuel flow path plate plays a vital role in achieving the aforementioned parameters. Further, the bipolar plates contribute 80% of the weight and 30%–40% of its total cost. Aim of this study is to enhance the efficiency of fuel to energy conversion and to minimize the overall cost of production.Design/methodology/approachThe authors have specifically designed, simulated and fabricated a standard 2.5 × 2.5 cm2 active area proton exchange membrane (PEM) FC flow path plate to study the performance by varying the flow fields in a single ladder, double ladder and interdigitated and varying channel geometries, namely, half curve, triangle and rectangle.FindingsUsing the 3D PEMFC model and visualizing the physical and electrochemical processes occurring during the operation of the FCs resulted in a better-performing flow path plate design. It is fabricated by using additive manufacturing technology. In addition, the assembly of the full cell with the designed flow path plate shows about an 11.44% reduction in total weight, which has a significant bearing on its total cost as well as specific energy density in the stack cell.Originality/valueSimultaneous optimization of multiple flow path parameters being carried out for better performance is the hallmark of this study which resulted in enhanced energy density and reduced cost of device production.

Interstitial carbon atoms enhance both selectivity and activity of rhodium catalysts toward C-C cleavage in direct ethanol fuel cells

Selective breaking of the C-C bond in ethanol holds the key to many industrial processes, including the operation of direct ethanol fuel cells and steam reforming. Interstitial C atoms in the subsurface region of noble-metal catalysts have major impacts on the selectivity and activity, but an understanding of the mechanistic details is still elusive due to their nature of in situ formation and metastability. Herein, we develop a method to obtain stable RhCx (x ≈ 0.5) by introducing C atoms into the interstitial sites of well-defined Rh nanosheets of 8–10 at. layers in thickness, and further elucidate the electronic and geometric effects of the interstitial C atoms on the cleavage of C-C bond. With the introduction of C atoms into half of the octahedral sites, the Rh lattice changes from a cubic to an orthorhombic structure. The lattice expansion induced by the insertion of C atoms, together with the electron transfer between C and Rh atoms, effectively suppresses the coupling reaction between OH* and CH3CO* to form acetic acid while making the cleavage of C-C bond more exothermic. As such, we obtain a selectivity of ethanol to CO2 as high as 18.1 %, much higher than those of the Rh counterpart (10.0 %), together with 3.1-fold improvement in kinetics. Guided by these findings, a new method is also developed to directly introduce C atoms into the subsurface of a commercial Rh black to enhance its selectivity and activity by 2.5- and 1.6- folds, respectively.

Efficient promotion of ethanol complete electrooxidation by anti-poisoning rhodium-bismuth alloy nanodendrites

Alkaline direct ethanol fuel cells are promising future energy technologies with a high energy-density, while the lack of robust anodic electrocatalysts limits their energy conversion efficiency due to serious poisoning and weak selectivity to the C1 pathway of ethanol oxidation reaction (EOR). Herein, rhodium-bismuth alloy nanodendrites (RhBi-NDs) are applied as an efficient and anti-poisoning electrocatalyst for EOR, which exhibit superior electrocatalytic performance, including a mass activity of 1068.9 mA mgRh−1 at 0.71 V, a 31.1% Faradaic efficiency for the C1 product, and an excellent stability of 40 h. The mechanism study indicates that Bi improves the oxidation ability of Rh to toxic intermediates by providing oxygen-containing species. The theoretical calculations disclose the electronic interaction between Bi and Rh, which tunes the adsorption energy of intermediates such as CH3CH2OH*, and CH3CO*, resulting in the suppression of C2 pathway and the promotion of C1 pathway for EOR on RhBi-NDs.

Enhancing electrochemical performance and membrane stability evaluation of carrageenan/polyvinyl alcohol-graphene oxide membrane in passive DEFCs

A good electrochemical performance of polymer electrolyte membranes (PEMs) is achieving high membrane selectivity, which is a result of low ethanol permeability and high proton conductivity. Reducing the thickness of PEMs is beneficial for high proton conductivity due to the short distance of proton diffusion. Unfortunately, it results in high ethanol permeability. Thus, achieving high membrane selectivity for good electrochemical performance by balancing the requirements of ethanol permeability and proton conductivity is a critical parameter of PEMs. In this paper, the thickness of the carrageenan/polyvinyl alcohol-graphene oxide membrane was varied from 15 μm – 30 μm to identify the optimum thickness for good electrochemical performance. With a 25 μm membrane thickness, the highest membrane selectivity was performed at 1.609 × 104 S s cm−3, and maximum power density in passive direct ethanol fuel cells was achieved at 14.5 mW cm−2, using 2.0 mg cm−2 anode catalyst loading and 2 M ethanol concentration at 70 °C, respectively. Furthermore, this membrane has sustained electrochemical performance for 1000 h at 70 °C without degrading the membrane stability.

Study on Commercially Available Membranes for Alkaline Direct Ethanol Fuel Cells.

This study provides a comparison of different commercially available low-cost anion exchange membranes (AEMs), a microporous separator, a cation exchange membrane (CEM), and an anionic-treated CEM for their application in the liquid-feed alkaline direct ethanol fuel cell (ADEFC). Moreover, the effect on performance was evaluated taking two different modes of operation for the ADEFC, with AEM or CEM, into consideration. The membranes were compared with respect to their physical and chemical properties, such as thermal and chemical stability, ion-exchange capacity, ionic conductivity, and ethanol permeability. The influence of these factors on performance and resistance was determined by means of polarization curve and electrochemical impedance spectra (EIS) measurements in the ADEFC. In addition, the influence of two different commercial ionomers on the structure and transport properties of the catalyst layer and on the performance were analyzed with scanning electron microscopy, single cell tests, and EIS. The applicability barriers of the membranes were pointed out, and the ideal combinations of membrane and ionomer for the liquid-feed ADEFC achieved power densities of approximately 80 mW cm-2 at 80 °C.

Palladium metallene confined on MXene with increased hydroxyl binding strength for highly efficient ethanol electrooxidation

Rational design and synthesis of high-performance electrocatalysts for ethanol oxidation reaction (EOR) is crucial to large-scale commercialization of direct ethanol fuel cells, but it is still an incredible challenge. Herein, a unique Pd metallene/Ti3C2Tx MXene (Pdene/Ti3C2Tx)-supported electrocatalyst is constructed via an in-situ growth approach for high-efficiency EOR. The resulting Pdene/Ti3C2Tx catalyst achieves an ultrahigh mass activity of 7.47 A mgPd-1 under alkaline condition, as well as high tolerance to CO poisoning. Insitu attenuated total reflection-infrared spectroscopy studies combined with density functional theory calculations reveal that the excellent EOR activity of Pdene/Ti3C2Tx catalyst is attributed to the unique and stable interfaces which reduce the reaction energy barrier of *CH3CO intermediate oxidation and facilitate oxidative removal of CO poisonous species by increasing the Pd-OH binding strength.

CoFe-Layered Double Hydroxide Coupled with Pd Particles for Electrocatalytic Ethanol Oxidation.

Electrocatalytic efficiency and stability have emerged as critical issues in the ethanol oxidation reaction (EOR) of direct ethanol fuel cells. In this paper, Pd/Co1Fe3-LDH/NF as an electrocatalyst for EOR was prepared by a two-step synthetic strategy. Metal-oxygen bonds formed between Pd nanoparticles and Co1Fe3-LDH/NF guaranteed structural stability and adequate surface-active site exposure. More importantly, the charge transfer of the formed Pd-O-Co(Fe) bridge could effectively modulate the electrical structure of hybrids, improving the facilitated absorption of OH- radicals and oxidation of COads. Benefiting from the interfacial interaction, exposed active sites, and structural stability, the observed specific activity for Pd/Co1Fe3-LDH/NF (17.46 mA cm-2) was 97 and 73 times higher than those of commercial Pd/C (20%) (0.18 mA cm-2) and Pt/C (20%) (0.24 mA cm-2), respectively. Besides, the jf/jr ratio representing the resistance to catalyst poisoning was 1.92 in the Pd/Co1Fe3-LDH/NF catalytic system. These results provide insights into optimizing the electronic interaction between metals and the support of electrocatalysts for EOR.

Shape-Controlled Ni Supported GDC Catalyst and its Application in Direct Ethanol Solid Oxide Fuel Cells

Matching catalytic activity with the high temperature heat treatments required to process solid oxide fuel cells (SOFCs) can be a challenge. Shape control is an interesting strategy to stabilize the surface of nanoparticles during heat treatments. In this study, nickel-based catalysts supported on shape-controlled (nanorods and nanocubes) gadolinium-doped cerium oxide (GDC) were evaluated for direct ethanol SOFCs. The morphology of the support had a significant effect on the catalytic activity. It was shown that the Ni catalyst supported on the GDC nanorods maintained high catalytic activity after heat treatments for catalytic layer sintering. Such catalyst was applied as a catalytic layer on a SOFC operating directly on anhydrous ethanol at 700 °C. The fuel cell operated for more than 100 h under 0.6 V displaying consistent performance with no indication of degradation from carbon deposition.

Template‐ and Surfactant‐Free Room Temperature Synthesis of Pt/C and Pt−Rh/C Nanowires/Nanoparticles for Ethanol Electro‐Oxidation

AbstractThe synthesis of Pt−Rh alloy nanowires (NWs) using straightforward methodologies remains a challenge. Here, carbon‐supported Pt and Pt−Rh nanowire catalysts were synthesised by chemical reduction at room temperature, without using surfactants or templates. The method of synthesis used yielded Pt/C NWs and a mixture of nanowires with some nanoparticles for the Pt−Rh/C catalysts (characterised using XRD, TEM, EDX, XPS, and XAS). The nanoparticles form due to differences in the surface energy and atomic radius between Pt and Rh. The binary NWs are found to be more active towards ethanol oxidation than the commercial Pt/C reference catalyst. Additionally, the Pt−Rh/C NW catalyst displays a specific activity 2.5‐fold higher than the Pt/C NWs and Pt/C reference catalysts after 15 min of chronoamperometric tests (at 0.5 V vs RHE). Thus, the synthesised carbon‐supported Pt NWs and Pt−Rh nanowires‐nanoparticles are promising alternatives for direct ethanol fuel cell anodes.