Direct Ethanol Research Articles

Comparative of heat transfer performance between a parallel serpentine-baffle flow field plate and a parallel flow field plate design in a direct ethanol proton exchange membrane fuel cell

The dependence on fossil fuels as an energy source causes serious environmental problems. Direct ethanol proton exchange membrane fuel cells (DE-PEMFCs) that directly convert the chemical energy stored in the etanol alcohol into electricity makes it promising as an environment-friendly power source for portable and mobile applications. Increasing the reagent operating temperature increases the electrochemical kinetics at the anode, increasing the cell power. However in a DE-PEMFC, the flow field plate directly interferes at the heat flow. As a result, the aim of this research were project a new parallel serpentine flow field plate with interdigitated characteristics, a parallel serpentine-baffle flow field plate (PSBFFP) and comparing with a PSFFP with respect to heat transfer performance in a DE-PEMFC anode side. The results show that the discontinue channels presents in the PSBFFP improve the heat transfer between plate and reagent, improving the reaction rate and consequently the fuel cell performance.

Use of commercial TiO2 as direct ethanol fuel cell electrocatalyst support

Direct ethanol fuel cells (DEFCs) are efficient converters of chemical energy into electrical energy. DEFCs operate at low temperatures, and an anode, a cathode and an electrolyte are the main constituents. In alkaline media, electrocatalysts, responsible for promoting anodic and cathodic reactions, are generally composed of palladium supported on carbon black. Other materials have been studied in order to make the ethanol oxidation reaction (EOR) more efficient. In this work, the effect of commercial TiO2 as alternative support to Pd-based catalysts for the EOR was evaluated. The synthesized materials were characterized by X-ray diffraction, linear voltammetry and chronoamperometry, aiming to determine the effect of different supports on the performance of the EOR.

Defect-rich Pt-Ru metallic aerogels for highly efficient ethanol oxidation reaction

Direct ethanol fuel cells (DEFCs) are a new type of green and efficient energy conversion devices, but the slow anodic reaction kinetics limit their application. Herein, a series of Pt-Ru metallic aerogels (MAs) with controllable composition, rich surface defects, and large specific surface area were prepared for ethanol oxidation reaction (EOR) by freeze–thaw method. Pt6Ru MAs exhibit the highest mass activity (1.264 A mgPt−1) toward EOR among all the catalysts we have prepared, which is 2.0, 1.8, and 3.7 times higher than those of Pt MAs (0.632 A mgPt−1), the commercial Pt/C (0.696 A mgPt−1), Pt6Ru NPs (0.339 A mgPt−1). 1H nuclear magnetic resonance spectroscopy confirms that only acetic acid was the liquid product of Pt6Ru MAs during EOR catalysis. Furthermore, Pt6Ru MAs show little attenuation and satisfactory reactivation abilities in stability assessment, demonstrating their good stability. This proves that the introduction of Ru makes feasible adjustments to the electronic structure of Pt in MAs, improving the electrocatalysis activity of Pt6Ru MAs in EOR. Mechanistic investigations reveal that the optimal electronic structure is the intrinsic reason for the excellent EOR performance of Pt6Ru MAs. The findings open a new way to develop high-performance Pt-based materials electrocatalysts.

Carbon Dots Modified Graphite as Novel Support Material for Low Lead (Pd) Loading Direct Ethanol Fuel Cell Catalyst

Carbon Dots Modified Graphite as Novel Support Material for Low Lead (Pd) Loading Direct Ethanol Fuel Cell Catalyst

High-entropy PtCuSnWNb nanoalloys as efficient and stable catalysts for ethanol oxidation electrocatalysis.

Ternary nanoalloys used as electrochemical ethanol oxidation catalysts for direct ethanol fuel cells are confronted with poor stability issues under harsh acidic operating conditions. To address this issue, a carbon-supported quinary PtCuSnWNb high-entropy nanoalloy (denoted as PtCuSnWNb/C) was synthesized by using a polyol reduction method. Due to the unique high-entropy mixing states and strong catalyst-support interactions, PtCuSnWNb/C shows robust structural and compositional stability.

Silver decorated nickel oxide nanoflake/carbon nanotube nanocomposite as an efficient electrocatalyst for ethanol oxidation.

The higher energy density and lesser toxicity of ethanol compared to methanol make it an ideal combustible renewable energy source in fuel cells. Finding suitable cost-effective electrocatalysts that can oxidize ethanol in ethanol-based fuel cells is a major challenge. With their high catalytic activity and stability in alkaline media, transition metal-based catalysts are ideal candidates for alkaline direct ethanol fuel cells. Nickel-based nanomaterials and composites exhibit high electrocatalytic activity, which makes them predominant candidates for the electrochemical oxidation of ethanol. In this study, the electrocatalytic activity of a nickel oxide flower-like structure was explored. Forming a nanocomposite of NiO in combination with carbon nanotubes (CNTs), NiO/CNTs, as a substrate led to an increase in the stability of the electrocatalyst in alkaline media. Furthermore, the electrocatalytic activity of the NiO/CNT nanocomposite was greatly enhanced by decorating the surface with different ratios of silver (Ag). Ag/NiO/CNT composites with different Ag ratios, namely, 25% and 50% by weight, were studied. The Ag 25%/NiO/CNT weight ratio showed a maximum ethanol conversion. At an ethanol concentration of 300 mM, the electrochemical oxidation current density was found to be 57.1 ± 0.2 mA cm-2 for the 25% by weight Ag ratio, with a five-fold increase in the current density (compared to NiO/CNTs (10 ± 0.34 mA cm-2)). Furthermore, the nanocomposite synthesized here (Ag 25%/NiO/CNTs) showed a significantly higher energy conversion (current per ethanol concentration) rate compared to other reported NiO-based catalysts. These results open real opportunities for designing high efficiency ethanol fuel cell catalysts.

Insight into the ordering process and ethanol oxidation performance of Au-Pt-Cu ternary alloys.

Direct ethanol fuel cells (DEFCs), which have been widely recognized as nontoxic and green energy conversion devices, show attractive application prospects for liquid hydrogen-carriers, due to the higher specific energy and lower toxicity of ethanol. Pt-based catalysts are widely used in DEFCs, while their poor poisoning resistance highlights the importance of composition and structure optimization. Herein, we synthesized a series of reduced graphene oxide supported ternary alloy AuxPt1-xCu3/rGO (x = 0-1) catalysts with excellent ethanol oxidation performance and a composition-dependent volcano plot trend of the ordering degree was observed and rationalized. The highest Pt-normalized mass activity of Au0.8Pt0.2Cu3/rGO is attributed to the optimized CO binding energy according to DFT calculations. This work not only provides an efficient EOR catalyst based on ordered alloys AuxPt1-xCu3 (x = 0-1), but also offers valuable insight into the role of a third metal in tuning the structure and function of alloys.

Silver and Silver Alloy on Carbon-supported Catalysts for Cathodes in Proton Exchange Membrane Fuel Cell and Direct Ethanol Fuel Cell

This research was focused on the synthesis of 20 %wt silver, silver platinum alloy, and silver-copper alloy catalysts on carbon Vulcan XC-72 supporter for proton exchange membrane fuel cell (PEMFC) and direct ethanol fuel cell (DEFC) cathode using sodium borohydride method. Herein, the ratio of silver and platinum or copper sources was 1:1 by weight. The obtained catalysts were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), and the electro-activity performance was investigated on single-cell testing. XRD and TEM results confirmed the catalytic products of the Ag metal, AgPt alloy, and silver copper oxide (AgxCu2-xO). Therefore, the particle size of the catalytic 20 %wt AgPt/C was observed in the smallest size of about 4.71±1.03 nm. The catalyst was selected for PEMFC and DEFC cathode testing. It showed high power density of 14.68 and 1.26 W/cm2.g(M), respectively.

In Situ Real-Time Simultaneous NMR Analyses of Anode and Cathode Exhausts of Direct Ethanol and Methanol Fuel Cells

Understanding the electrochemical reaction mechanisms of energy conversion and storage systems is essential for improving their performance. Nuclear magnetic resonance (NMR) spectroscopy is excellent for probing electrochemical reactions due to its capability to provide quantitative and qualitative information. For the in situ simultaneous acquisition of the anode and cathode exhaust spectra of direct alcohol fuel cells such as a direct methanol fuel cell (DMFC) or direct ethanol fuel cell (DEFC), real-time flow-NMR spectroscopy using a toroid cavity detector was developed in our laboratory. In the cathode exhaust of DMFC, the CD3OH crossed over from the anode as well as HOD was observed. Ex situ NMR spectroscopy cannot detect gas products because they are lost during sample preparation. On the other hand, the amount of CO2 gas detected in the anode exhaust using our in situ detection method was proportional to the HOD amount. It was also proportional to the cell current generated. This explains differences in the fuel cell performance by identifying generated and consumed chemicals and their pathways in the cells at respective conditions. Analyses of DEFC exhausts showed various reaction products such as acetic acid and acetaldehyde but CO2 gas detected was negligible. Our results show that this in situ real-time analysis could identify and quantify the exhaust components, including the gaseous products. Therefore, our results demonstrate that this in situ real-time analysis is appropriate to study the reaction mechanisms of diverse other liquid-flowing electrochemical systems in addition to fuel cells. Furthermore, it may be applicable to designing advanced materials for the systems.

One-step growth of RuNi-MOF nanoarrays on carbon felt host as a high-performance binder-free electrode for dual application: Ethanol fuel cell and supercapacitor

The future perspective is to develop high-efficient catalysts in next-generation energy technologies. Metal-organic frameworks (MOFs) offer a high degree of design flexibility which plays an important role as electrocatalysts. However, poor stability and low conductivity of MOFs are challenging to favorable electrocatalytic activity. Accordingly, a new and efficiently bimetallic RuNi-MOF is fabricated by in-situ growth of 3D nanoscale of MOFs on a 3D network of carbon felt (CF) to enhance the practical applicability of direct ethanol fuel cells (DEFCs) and supercapacitors (SCs). The RuNi-MOF/CF displays remarkable performance for SCs (the high specific capacitance of 1173.7 mF cm−2 (810.8 F g−1) at 6 mA cm−2, a high energy density of 145.9 Wh kg−1 and a power density of 6 kW kg−1 with cyclic retention of 95 %) and as an anode in DEFCs (peak current density of 84.6 mA cm−2 and power density of 70.2 mW cm−2 at 60 °C). The electron/ion transport ability and electrocatalytic performance of RuNi-MOF are enhanced due to the incorporation of Ru about 1.0 %. The success is attributed to the synergistic effects between Ru, Ni, and conductive CF. This work highlights a new understanding of using high-performance materials to improve electrocatalytic activity.

Electrocatalytic ethanol-to-CO2 selectivity on the Ir electrode: A quasi-quantitative electrochemical infrared absorption spectroscopic investigation

Ir has long been regarded as an alternative ethanol-to-CO2 electrocatalyst, but little is known about the ethanol oxidation reaction (EOR) mechanism on Ir, especially the C1 pathway selectivity. Thereby, in situ quasi-quantitative electrochemical infrared absorption spectroscopy (QEIAS), consisting of total-reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS), infrared absorption spectroscopy (IRAS), and transmission infrared absorption spectroscopy (TIAS) with a thin-layer flow cell, is established to probe it. Initially, the well-accepted EOR dual-pathway mechanism is confirmed via ATR-SEIRAS and IRAS. Ir-Had species (ca. 2040 cm−1), originating from the ethanol dissociation at low potentials, are observed for the first time to replenish the reaction process. Based on it, the apparent Faradaic efficiency of the C1 pathway (FEC1) is readily estimated to be as high as 76.4% (0.7 V) in acidic media. The quantitative analysis of reaction residual verifies these FEC1 results through high-performance liquid chromatography (HPLC), and a relative error of only 2–9% exists between the two methods. Thus, Ir might be more efficient for ethanol complete oxidation than other Pt-group metallic catalysts, especially in acidic media. This work could be necessary for the rational design of Ir-based EOR catalysts with high C1 pathway selectivity and low over-potential for direct ethanol fuel cells.

Titanium Oxycarbide as Platinum-Free Electrocatalyst for Ethanol Oxidation.

The compound material titanium oxycarbide (TiOC) is found to be an effective electrocatalyst for the electrochemical oxidation of ethanol to CO2. The complete course of this reaction is one of the main challenges in direct ethanol fuel cells (DEFCs). While TiOC has previously been investigated as catalyst support material only, in this study we show that TiOC alone is able to oxidize ethanol to acetaldehyde without the need of expensive noble metal catalysts like Pt. It is suggested that this behavior is attributed to the presence of both undercoordinated sites, which allow ethanol to adsorb, and oxygenated sites, which facilitate the activation of water. This is a milestone in DEFC research and development and opens up innovative possibilities for the design of catalyst materials for intermediate temperature fuel cells.

Transition metal oxide-polymer composite supported PtPd/PNVC-WO3 nano-catalyst: Multifaceted functional behavior boosting the performance of ethanol oxidation kinetics

This investigation involves synthesis of PtPd catalyst nano-particles supported on tungsten oxide (WO3) and poly-N vinyl carbazole (PNVC) composite for validation in ethanol oxidation reaction. The tungsten oxide acquires excellent functional property by hydrogen spill over phenomenon that facilitates hydrogen tungsten bronze formation while conducting polymer enhances the charge transfer ability within the direct ethanol fuel cell framework. The catalyst nano-particles are found to be in the size range 3–5 nm, revealed from structure and morphology studies. Electrochemical characterizations derive output power density of ∼54 mW cm−2 and mass activity ∼1.9 A/mgPt, in terms of specific current density for ethanol oxidation. Ion chromatographic analysis quantifies the reaction intermediates, acetate and carbonate to the extent of 396 and 280 ppm using 1 M ethanol solution. Self designed composite nano-structures of PtPd/PNVC-WO3 with reduced Pt share provide astounding opportunity for the catalytic reaction to gear up to the complete oxidation kinetics.

Ni-based metal organic frameworks doped with reduced graphene oxide as an effective anode catalyst in direct ethanol fuel cell

Direct ethanol fuel cells (DEFCs), with their boosted energy density and efficiency, are poised to supplant secondary batteries in the near future. However, the pricy and low-durability of Pt-based anode catalyst used in these cells have hampered the development of this technology. We successfully created a Ni-MOF @ nickel foam (NF) to operate as an anode for a DEFC. We next enhanced the electrical conductivity of these produced electrodes with graphene and tested them towards ethanol oxidation in a basic solution. The study looked at the electrodes' surface shape, crystalline structure, chemical and electrical properities, among other things. Furthermore, the electrochemical activity and durability of the prepared electrodes were examined. These tests demonstrated the successful formation of the MOF @ the surface of the NF, with and without reduced graphene oxide. The produced materials outperformed plain Ni foam in terms of ethanol oxidation activity, and the graphene doping significantly enhanced this activity. A 0.35 V onset potential was obtained, with current output increasing concurrently with ethanol oxidation up to 0.5 M before stabilizing. The superior activity was attributed to the prepared electrodes' perfect nano-sheet structure, high porosity, and outstanding mass and charge transport characteristics. The addition of reduced graphene oxide enhanced charge transfer and thus improved the overall performance.

Alkali Metal Cation-Sulfate Anion Ion Pairs Promoted the Cleavage of C-C Bond During Ethanol Electrooxidation.

Direct ethanol fuel cells show great promise as a means of converting biomass ethanol derived from biomass into electricity. However, the efficiency of complete conversion is hindered by the low selectivity in breaking the C-C bond. This selectivity is determined by factors such as the material structure and reaction conditions, including the nature of the supporting electrolyte. Cations serve not only as facilitators of electricity conduction through ion migration but also as influencers of the reaction pathways. In this study, we utilized differential electrochemical mass spectrometry to track the in situ generation of CO2 during potential scanning. The presence of alkali cations led to an enhancement in the CO2 selectivity. In addition, in situ Raman spectroscopy provided evidence of the formation of alkali metal cation-sulfate anion ion pairs. The catalytic activity and CO2 selectivity were found to be directly correlated to the ionic strength of these ion pairs.

Environmental impact assessment of a novel third-generation biorefinery approach for astaxanthin and biofuel production

A novel third-generation biorefinery approach, including two paths of Ethanol/methane production pathway (EMP) and the direct methane production pathway (DMP), for astaxanthin and ethanol and biogas production from the freshwater microalgae Haematococcus pluvialis was developed previously. To ensure its environmental sustainability, a comprehensive life cycle assessment (LCA) study was conducted based on 1-GJ energy generation from biomethane as the functional unit. Results indicate that the EMP pathway had higher environmental impacts on all categories due to more stages and chemicals/energy consumption (at least five times greater effect). Results showed that while the enzymatic hydrolysis step followed by the fermentation stage was the main contributor to all environmental categories in the EMP route, astaxanthin induction dominated all environmental categories in the DMP route. The results showed that sodium nitrate, phosphate salts, inoculum sludge, acetone, and electricity had considerable environmental impacts. Moreover, despite low enzyme usage in enzymatic hydrolysis, these proteins significantly impacted all environmental categories in this stage. The baseline analysis concluded that to produce 1 GJ energy from methane, about 88 kg and 13 kg CO2 were generated from the EMP and DMP pathways, respectively. A sensitivity analysis was also conducted to compare various ratios of chemicals, such as phosphate salts, with high contributions to enzymatic hydrolysis and astaxanthin induction stages in the EMP and DMP routes, respectively. Finally, the LCA results revealed that the DMP pathway is more environmentally friendly with the same economic value of biomethane and astaxanthin production. This LCA study updated the data related to the environmental assessment of processes to utilize H. pluvialis to produce biofuels and astaxanthin simultaneously.

Composition engineering of carbon nanotubes supported PtxRhRu ultrafine nanocatalysts for ethanol electro-oxidation: Elucidating the role of trimetallic sites

The practice of direct ethanol fuel cells (DEFCs) is hindered by insufficient activity of anode Pt-based catalyst for ethanol oxidation reaction (EOR), while alloying Rh and Ru to Pt is hopeful to solve the problem by simultaneously enhancing CC cleavage and decreasing poisoning; and Ru owning better stability and activity than usually doped Sn in alkaline electrolyte. Nevertheless, Pt-Rh-Ru catalysts were rarely reported. In this work, to avoid random trials, the “composition engineering” strategy was applied to design PtxRhRu catalysts. The optimal x range was predicted by DFT. Then, carbon nanotubes supported PtxRhRu ultrafine nanoparticles (PtxRhRu/CNTs) were synthesized and characterized. The synthetic mechanism was also studied. EOR tests show that, in line with the forecast, Pt4RhRu/CNTs (∼1.9 nm) exhibit the highest activity (5.85 mA·cm−2), 6.97 times of commercial Pt/C, and higher than most reports. The selectivity, stability and durability are also excellent. DFT analysis reveals the role of Pt-Rh-Ru site for the first time, that the optimal route on PtxRhRu is changed. New route clearly enhances complete ethanol oxidation and reduces poisoning. Bifunctional mechanism on Pt-Rh-Ru site was also confirmed. This study may provide new perspective for material design; the products are also promotive for DEFCs into practice.

Abstract 15111: The Combination of Vagal Nerve Stimulation and Intra-Aortic Balloon Pumping Rapidly Modulates Heart Rate and Cardiac Load While Maintaining Hemodynamics in a Dog Model of Acute Heart Failure

Background: In acute heart failure (AHF) condition, excessive tachycardia increases myocardial oxygen consumption (MVO 2 ). Recently, we have developed an intravenous vagal nerve stimulation (iVNS) catheter which can stimulate right vagal nerve and induce HR reduction (Fig. 1). Since inappropriate bradycardia in AHF condition leads to hemodynamic instability, the use of intra-aortic balloon pumping (IABP) may serve as a beneficial adjunctive therapy for iVNS. Methods: We induced AHF by the direct ethanol injection (0.5-2 ml/kg) to myocardium. The specialized basket catheter was inserted through the right femoral vein and placed in the superior vena cava. The IABP with 20-cc balloon was inserted through left femoral artery. We also calculated MVO 2 by the product of coronary flow and the difference of oxygen saturation between coronary artery and coronary sinus. We compared HR, MVO 2 , and hemodynamics between baseline and 3-min after iVNS (n=11). In addition, we examined the impact of IABP on hemodynamics during iVNS in AHF condition (n=8). Results: The direct ethanol injection increased LAP (+3.6±7.2 mmHg) and decreased left ventricular ejection fraction (-28±9.8%). The iVNS (20Hz, 10-22 V) rapidly reduced HR (-13±6.9%, P<0.01) and MVO2 (-11±8.1%, P<0.05), while slightly decreased CO (-10±7.3%) and increased LAP (+2.0±3.5 mmHg) (Fig. 2). An adding of IABP during iVNS increased CO (1.2±0.24 vs. 1.3±0.30 l/min, P<0.05) and decreased LAP (14±8.6 vs. 13±8.2 mmHg, P<0.05) . Conclusion: The combination of iVNS and IABP shows clinical potential as a novel therapy for effectively modulating excessive cardiac load in cases of unstable hemodynamics.

Synthesis of Pd-Cu/TPPCu electrocatalyst for direct ethanol fuel cell applications

In this study, the electro-oxidation reaction of ethanol over Pd–Cu supported on Cu porphyrin (TPPCu) was investigated. The catalyst was synthesized using the microwave-assisted polyol method and physicochemically characterized by XRD, XPS, SEM, EDS, TEM, EDAX, UV–Vis, FTIR, and RBS. A Cu-enriched catalyst with Cu3Pd, Pd,Cu, and TPPCu phases was identified using XRD and XPS. However, according to the RBS results, the catalytic surface was enriched with Pd, indicating that the interaction between TPPCu and Pd–Cu allowed the presence of Pd on the surface, thus enhancing the catalytic response of the material. This synthesis prevented the deprotonation of porphyrin on the electrocatalyst, as confirmed by XPS analysis. Electrochemical studies based on cyclic voltammetry and electrochemical impedance spectroscopy were used to investigate the response of the catalyst to variations in the scan rate and increasing ethanol concentration. The electrochemical response of PdCu/TPPCu improved with an increasing number of cycles, indicating improved mass transport, thus improving its electrochemical response and tolerance to CO contamination. This catalyst exhibited a high electroactive surface area of 49.4 m2/g, which could be related to the presence of TPPCu as a support. The behavior of the catalyst on the anode of a fuel cell fed with ethanol, bioethanol, and bioethanol residues was evaluated.Graphical

Electrodeposition of CoNi Bimetallic Catalyst for Ethanol Electrooxidation Application

Platinum is potentially employed as a catalyst in direct ethanol fuel cells (DEFCs). However, its scarcity and susceptibility to carbon monoxide poisoning give rise to novel challenges necessitating resolution. Transition metals such as nickel and cobalt are regarded as highly auspicious catalysts for DEFCs due to their perceived potential to reduce the expenditure associated with the synthesis procedure. In the present investigation, the synthesis of a cobalt-nickel (CoNi) catalyst with bimetallic properties was effectively accomplished through the electrodeposition technique utilizing the stimulator mode. Subsequently, an evaluation was conducted to assess the catalyst's proficiency in ethanol electrooxidation. The CoNi samples underwent comprehensive characterization through the utilization of various analytical techniques, namely X-ray diffraction (XRD), scanning electron microscopy (SEM), elemental dispersive X-ray analysis, and electrochemical impedance spectroscopy (EIS). The XRD analysis confirmed the formation of CoNi, while the SEM characterization demonstrated that the CoNi samples exhibited a homogeneous morphological feature. The impedance measured by the EIS technique displayed a resistance to charge transfer value of 21.21 kΩ, while the solution resistance value amounted to 66.67 kΩ. The catalytic efficiency of the specimens in ethanol electrooxidation was evaluated using the cyclic voltammetry technique, resulting in a peak current density of 3.14 mA/cm2 proving the potential of bimetallic CoNi to be a low-cost catalyst for ethanol electrooxidation process.