Alkaline Direct Ethanol Fuel Cells Research Articles

Interfacial Electronic Interactions within the Pd-CeO2/Carbon Onions Define the Efficient Electrocatalytic Ethanol Oxidation Reaction in Alkaline Electrolytes.

Porous Pd-based electrocatalysts are promising materials for alkaline direct ethanol fuel cells (ADEFCs) and ethanol sensors in the development of renewable energy and point-of-contact ethanol sensor test kits for drunk drivers. However, experimental and theoretical investigations of the interfacial interaction among Pd nanocrystals on supports (i.e., carbon black (CB), onion-like carbon (OLC), and CeO2/OLC) toward ADEFC and ethanol sensors are not yet reported. This is based on the preparation of Pd-CeO2/OLC nanocrystals by the sol-gel and impregnation methods. Evidently, the porous Pd-CeO2/OLC significantly increased membrane-free micro-3D-printed ADEFC performance with a high peak power density (Pmax = 27.15 mW cm-2) that is 1.38- and 7.58-times those of Pd/OLC (19.72 mW cm-2) and Pd/CB (3.59 mW cm-2), besides its excellent stability for 48 h. This is due to the excellent interfacial interaction among Pd, CeO2, and OLC, evidenced by density functional theory (DFT) simulations that showed a modulated Pd d-band center and facile active oxygenated species formation by the CeO2 needed for ethanol fuel cells. Similarly, Pd-CeO2/OLC gives excellent sensitivity (0.00024 mA mM-1) and limit of detection (LoD = 8.7 mM) for ethanol sensing and satisfactory recoveries (89-108%) in commercial alcoholic beverages (i.e., human serum, Amstel beer, and Nederberg Wine). This study shows the excellent possibility of utilizing Pd-CeO2/OLC for future applications in fuel cells and alcohol sensors.

High performance chitosan/nanocellulose-based composite membrane for alkaline direct ethanol fuel cells

Polysaccharide anion exchange membranes (AEMs) containing chitosan (CS), cellulose nanofibrils (CNFs) and CNFs quaternized with poly(diallyldimethylammonium chloride) (CNF(P)s) were developed for use in alkaline direct ethanol fuel cells (ADEFCs). The resulting composite membranes prepared by the solvent casting process based on an experimental design were comprehensively assessed for morphology, KOH uptake, swelling ratio, EtOH permeability, mechanical properties, ionic conductivity, and cell performance. The fabricated CS-based composite membranes with CNF(P) fillers were superior to the commercial Fumatech FAA-3-50 membrane in terms of Young's modulus and tensile strength (69 % and 85 % higher, respectively), ion exchange capacity (169 % higher), and ionic conductivity (228 % higher). Single fuel cell tests have shown excellent performance of the CS-based membranes with CNF and CNF(P) fillers, as they exhibited up to 86 % improvement in power density at 80 °C compared to the commercial membrane (65.1 mW/cm2 vs. 35.1 mW/cm2) and higher maximum power density at all test conditions.

Influence of the Electrode Deposition Method of Graphene-Based Catalyst Inks for ADEFC on Performance.

The utilization of graphene as a catalyst support has garnered significant attention due to its potential for enhancing fuel cell performance. However, a critical challenge in electrode production still lies in the electrode preparation technologies and the restacking of graphene sheets, which can greatly impact the fuel cell performance alongside with catalyst development. This study aimed to investigate the impact of different electrode deposition methods for N-rGO-based catalyst inks on catalyst layer morphology, with a specific focus on graphene sheet orientation and its influence on the performance of alkaline direct ethanol fuel cells (ADEFCs). The dispersion behavior and ink stability of the catalysts were assessed using ultraviolet-visible light (UV-vis), ζ potential, and dynamic light scattering techniques. The morphology and physical properties of the gas diffusion electrodes (GDEs) were analyzed through Brunauer-Emmett-Teller measurements, contact angle measurements and scanning electron microscopy (SEM) combined with energy-dispersive spectroscopy. The electrochemical behavior was evaluated both ex-situ, utilizing half-cell GDE measurements, and in situ, through single-cell tests. The N-rGO-based membrane electrode assembly, comprising Pt-free catalysts and a biobased membrane, exhibited outstanding performance in ADEFCs, as evidenced by high maximum power density values and long-term durability. The N-rGO-based membrane electrode assembly has demonstrated remarkable potential for high-performance fuel cells, presenting an exciting avenue for further exploration.

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.

Reduced graphene oxide as efficient carbon support for Pd-based ethanol oxidation catalysts in alkaline media

The sluggish kinetics of the ethanol oxidation reaction (EOR) and the related development of low-cost, highly active and stable anode catalysts still remains the major challenge in alkaline direct ethanol fuel cells (ADEFCs). In this respect, we synthesized a PdNiBi nanocatalyst on reduced graphene oxide (rGO) via a facile synthesis method. The prepared composite catalyst was physicochemically characterized by SEM, STEM, EDX, ICP-OES and XRD to analyze the morphology, particle distribution and size, elemental composition and structure. The electrochemical activity and stability towards EOR in alkaline media were examined using the thin-film rotating disk electrode technique. The results reveal well-dispersed and strongly anchored nanoparticles on the rGO support, providing abundant active sites. The PdNiBi/rGO presents a higher EOR activity and stability compared to a commercial Pd/C ascribed to a high ECSA and synergistic effects between Pd, Ni and Bi and the rGO material. These findings suggest PdNiBi/rGO as a promising anode catalyst in ADEFC applications.

Fabrication of dendritic PdCu alloy supported on 3D N-doped hollow graphene for efficient ethanol electrooxidation.

Fabricating highly efficient Pd-based nanocatalysts with a well-defined structure is desired for the commercialization of direct ethanol fuel cell (DEFC). Herein, a series of hierarchical three-dimensional N-doped hollow graphene spheres (NHGS) supported dendritic PdCu alloy catalysts PdxCu(d)-NHGS (x: Cu/Pd theoretical molar ratio of 4, 2, and 1) are assembled by one-pot ascorbic acid reduction-immobilization method. Aiming to maximize the Pd utilization and realize the efficient ethanol electrooxidation, this novel electrocatalyst offers potent activity sites and promotes electron and ion kinetics simultaneously. Characterization indicates that the as-obtained Pd4Cu(d) alloy nanoparticles with average sizes of approximately 55 nm are evenly dispersed on the NHGS supporting materials obtained by using the SiO2 nanospheres template strategy. Three catalysts all exhibit enhanced electrocatalytic activity, of which the Pd4Cu(d)-NHGS shows the highest mass current activity (2683 mA mgPd-1), which is 2.59 times of the commercial Pd/C toward ethanol electrooxidation in alkaline medium. Based on the results, we believed that the Pd4Cu(d)-NHGS could exhibit extensive application prospect in alkaline DEFC.

Effect of PdNiBi Metal Content: Cost Reduction in Alkaline Direct Ethanol Fuel Cells

In this work, the metal content of Pd85Ni10Bi5/C catalysts for the alkaline ethanol-oxidation reaction was reduced from 40 wt.% (PdNiBi/C (40/60)) to 30 wt.% (PdNiBi/C (30/70)), 20 wt.% (PdNiBi/C (20/80)) and 10 wt.% (PdNiBi/C (10/90)), while increasing performance. The synthesized catalysts were examined using physicochemical measurements and electrochemical measurements. The best performing catalysts were used to fabricate membrane electrode assemblies for carrying out single-cell tests and to determine the influence of the metal/carbon ratio of the electrode. The electrochemical surface area (695 cm2 mg−1) and activity were increased, resulting in high peak-current densities for the ethanol oxidation reaction (3.72 A mg−1) by the resulting more accessible metal particles. The electrode produced with the PdNiBi/C (30/70) catalyst reached a maximum power density of 34.8 mW mg−1 at 50 °C. This successfully demonstrated a doubling of the power density compared with the performance of the PdNiBi/C (40/60) electrode, while simultaneously reducing the costs.

Alkaline Direct Ethanol Fuel Cell: Effect of the Anode Flow Field Design and the Setup Parameters on Performance

Alkaline direct ethanol fuel cells (DEFCs) represent an efficient energy conversion device for sustainable ethanol fuel. In this study, a design with new structural parameters for the anodic flow field of the alkaline DEFC was modeled with the aid of computational fluid dynamics and was then actually constructed. Single-cell tests were performed to evaluate the impact of the developed design on fuel cell performance. The results show that fuel cell performance significantly increased when using the improved design in the low-temperature range. The higher the temperature in the cell, the lower the influence of the flow field structure on performance. In addition, the influence of external factors, such as the orientation of the cell, the preheating of the fuel, and the direction of the two fuel flows relative to each other (co-current and counter-current), are shown.

Ag-MnxOy on Graphene Oxide Derivatives as Oxygen Reduction Reaction Catalyst in Alkaline Direct Ethanol Fuel Cells

In this study, Ag-MnxOy/C composite catalysts deposited on reduced graphene oxide (rGO) and, for the first time on N-doped graphene oxide (NGO), were prepared via a facile synthesis method. The influence of the carbon support material on the activity and stability of the oxygen reduction reaction (ORR) and on the tolerance to ethanol in alkaline medium was focused and investigated. The physicochemical properties of the Ag-MnxOy/C catalysts were analyzed by X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), Brunauer–Emmett–Teller (BET) method, atomic absorption spectroscopy (AAS), inductively coupled plasma-mass spectrometry (ICP-MS), and thermogravimetric gas analysis (TGA). Electrochemical characterization was performed by rotating disk electrode (RDE) experiments. The results show that the active manganese species MnO2 was assembled as nanorods and nanospheres on rGO and NGO, respectively. Ag was assumed to be present as very small or amorphous particles. Similar redox processes for Ag-MnxOy/rGO and Ag-MnxOy/NGO were examined via cyclic voltammetry. The Ag-MnxOy/rGO resulted in a more negative diffusion limiting current density of −3.01 mA cm−2 compared to Ag-MnxOy/NGO. The onset potential of approximately 0.9 V vs. RHE and the favored 4-electron transfer pathway were independent of the support material. Ag-MnxOy/NGO exhibited a higher ORR stability, whereas Ag-MnxOy/rGO showed a better ethanol tolerance.

Boosting the performance of alkaline direct ethanol fuel cell with low-Pd-loading nickel foam electrode via mixed acid-etching

Nickel foam has been widely used as an electrode supporting material for alkaline direct ethanol fuel cells (ADEFC). However, the smooth skeleton surface of pristine nickel foam results in low specific surface area, such that a high-load catalyst is required to deal with ethanol oxidation, which limits its application as a catalyst support. Therefore, efforts to enhance the roughness of skeleton surface and reduce the catalyst loading have been intensively made. One of the conventional approaches is hydrochloric acid (HCl) etching method, which can remove the inert layer but does not change the surface roughness. In this paper, a mixed acids treated nickel foam anode with low Pd loading (0.35 mg cm −2 ) is prepared by simply soaking for three times for ADEFC performance testing. The peak power density reaches 30 mW cm −2 , which is double the performance of the HCl treated anode. The performance improvement is attributed to the micro-holes produced by mixed acids etching, which enhance the roughness of skeleton and improve electrochemical active surface area (ECSA) of the catalyst. This work opens a new platform for in-depth exploration on metal foam electrodes in fuel cells. • Low duration (15 s) etching of mixed acids enriches the surface roughness of the nickel foam. • The palladium/nickel foam anode is prepared by simply soaking for three times. • This novel anode shows 30 mW cm −2 of peak power density, even with low Pd loading at 0.35 mg cm −2 .

Pd-Pt nanoparticles combined with ceria nanorods for application in oxygen reduction reactions in alkaline direct ethanol fuel cell cathodes

Fuel cells are important energy conversion devices. However, challenges in this regard are still noted, such as low electrocatalyst efficiencies in the oxygen reduction reaction (ORR), which occurs slowly in electrocatalyst cathodes. In this sense, this study aimed to synthetize hybrid binary and ternary electrocatalysts formed by palladium and platinum alloy nanoparticles and ceria nanorods (CeO2 NR) supported on carbon black Vulcan XC-72 (PdxPty/Vn and (Pd3Pt1)x(CeO2 NR)y(Vn)z) for the study of the oxygen reduction reaction (ORR) and application as alkaline direct ethanol fuel cells (ADEFCs) cathodes. The binary and ternary hybrid electrocatalysts were characterized using different physicochemical and electrochemical techniques. The ternary hybrid electrocatalyst, (Pd3Pt1)15(CeO2 NR)10(Vn)75, reached higher open circuit voltage (OCV), maximum current and power densities, of 1.13 V, 219 mA cm-2 and 61 mW cm-2, respectively, compared to the commercial Pt/C Alfa Aesar (AA) and other evaluated electrocatalysts. The ternary hybrid electrocatalyst, (Pd3Pt1)15(CeO2 NR)10(Vn)75, is interesting for application as an ADEFC cathode targeting the ORR, due to an almost 3-fold maximum power density and almost twice the maximum current density compared to a commercial electrocatalyst with the same noble metal loading, explained by increased defects and oxygenated species in this electrocatalyst as revealed by Fourier Transform Infrared Spectroscopy (FT-IR) and Raman analyses.

Performance Tests of Poly(vinyl alcohol)-Based Membranes for Alkaline Direct Ethanol Fuel Cells

Alkaline direct ethanol fuel cells (ADEFCs) are capable of converting ethanol, a CO2 neutral fuel, into electrical energy, which is why interest in this technology has been growing rapidly in recent decades. An important component, as it contributes significantly to the efficiency and performance of these fuel cells, is the anion exchange membrane (AEM). Nowadays, commercially available polymer AEMs have limiting properties for application in fuel cells: low thermal, chemical and mechanical stability and conductivity, moreover they are not environmentally friendly and expensive. Therefore, it is important to ensure the following properties for AEMs for optimal fuel cell operation: high hydroxide ion conductivity, low ethanol permeability, no electron conduction, and high thermal and chemical stability. In this study, Poly(vinyl alcohol) (PVA), a low cost polyhydroxy polymer was tested as main-backbone for the membrane because of its promising properties: it is hydrophilic, has low ethanol permeability, is non-toxic and crosslinking susceptible. Glutaraldehyde (GA)-based crosslinked (improvement of chemical stability of the membrane and reduction of membrane swelling) AEMs with PVA as backbone polymer were prepared and the performance of the membrane was examined in an ADEFC and compared to a commercial FAA-3 fumasep® membrane [1].The following preparations were made before performing the single cell test. Both membranes (the self-made PVA-based and the commercial FAA-3 fumasep® membrane) were pretreated by immersing them in 1 M KOH for 24h followed by excessive washing with ultrapure water. The PdNiBi/C anode catalyst [2] and the commercial PtRu/C cathode catalyst inks were deposited using an automatic ultrasonic spray coater on the gas diffusion layers (GDLs): carbon cloth and carbon paper, respectively. A metal loading of 0.75 mg cm-2 for the ethanol oxidation reaction and 0.5 mg cm-2 for the oxygen reduction reaction on the electrodes was achieved. The electrodes and the membrane were sandwiched together to prepare the membrane electrode assembly, which was inserted into the fuel cell. A mixture of 1 M KOH and 1 M EtOH with a flow rate of 5 mL min-1 served as anode fuel and oxygen gas with a flow rate of 25 mL min-1 as cathode feed gas. Different operational temperatures were used for the measurements: RT, 36°C, 44°C, 53°C, 57°C. A Gamry Reference 600TM Potentiostat was used to determine the current densities (I) and cell potentials (V) to plot the typical I-V and I-P curves.The I-V (left axis, open symbols) and I-P (right axis, filled symbols) plots as well as the temperature dependency of the maximum power density of the PVA-based membrane can be seen in Figure 1. The maximum power density increases with temperature because of the better reaction kinetics and higher conductivity. The best performance was achieved at an operation temperature of 57°C: 8.6 mW cm-2 at a current density of 47.6 mA cm-2. The commercial membrane in comparison at the same measurement conditions showed only 5.4 mW cm-2 at a current density of 27.0 mA cm-2. The higher maximum power density of the GA crosslinked PVA-based membrane can be linked to the better conductivity of the membrane.The results from the single cell tests of the prepared PVA-based membrane compared to the commercial membrane indicate that PVA-based membranes can be applied for future membranes in ADEFCs. Further details and results will be discussed in the presentation.The authors acknowledge the financial support by the Austrian Science Fund (FWF I 3871-N37).[1] A. M. Samsudin, S. Wolf, M. Roschger, V. Hacker, International Journal of Renewable Energy Development, 2021, 10(3), 435-443.[2] B. Cermenek, B. Genorio, T. Winter, S. Wolf, J. G. Connell, M. Roschger, I. Letofsky-Papst, N. Kienzl, B. Bitschnau, V. Hacker, Electrocatalysis, 2020, 11, 203-214. Figure 1

Graphene Derivatives As Carbon Support Material in Alkaline Direct Ethanol Fuel Cells

The increasing global demand for energy and the associated rise in CO2 emissions due to the use of fossil fuels require the development and use of renewable energy sources. In this context, fuel cells are identified as one of the key technologies for clean energy production. Nevertheless, there are three critical technical barriers for fuel cells that limit their commercialization: performance (activity), durability (stability) and cost. Alkaline fuel cells, particularly alkaline direct ethanol fuel cells (ADEFCs), have attracted much attention in recent decades because ethanol fuel is easy to handle, store, and transport, has low cost, and is environmentally friendly.ADEFCs are limited by their slow kinetics, especially the electrochemical reaction at the anode. Currently, no catalyst is available that cleaves the carbon-carbon bond of ethanol, resulting in a CO2 efficiency of 100% (C1 pathway). The ethanol oxidation reaction (EOR) in alkaline media is incomplete and predominantly follows the C2 pathway. Ethanol is oxidized by hydroxide ions to acetate as the main oxidation product and 4e- instead of 12e-, CO2 and water are released during the complete oxidation. During EOR, acetate is adsorbed on the catalyst surface as the active species. Nevertheless, various reaction intermediates deactivate the catalyst due to poisoning of the active sites, thus reducing the EOR performance. Palladium is currently the most suitable catalyst to replace platinum in ADEFCs. Palladium precursor salts are also cheaper than platinum salts and Pd/C catalysts show higher EOR activity (ethanol oxidation reaction) than Pt/C under alkaline conditions. This can be attributed to the higher oxophilic properties and the inherent ability of Pd to cleave C-C bonds. This positive effect also results in higher stability and lower susceptibility to poisoning of the active sites of the Pd catalyst during EOR. In addition, many non-precious metal co-catalysts are available for palladium, which further reduce the material cost while improving the catalytic activity, by-product tolerance and stability for alkaline EOR [1,2].The development of new anode catalysts with high activity and stability towards alkaline EOR is essential to improve the performance of direct ethanol fuel cell. Carbon materials, especially N-doped or reduced graphene oxides (rGO), are a promising catalyst support due to their low cost, high electrical conductivity, large surface area, and reasonable stability [3]. The deposition of the metal nanoparticles on the graphene oxide support generates a higher active surface area of the catalysts, which increases the electrocatalytic activity while reducing the cost.In the current studies, palladium-based catalysts are synthesized with different graphene oxide (GO) support materials (N-doped GO and rGO) by the modified instant method. The prepared catalysts were characterized ex-situ by the thin film rotating disk electrode technique using a standard three-electrode setup. To determine the electrochemical active surface area and EOR activity, cyclic voltammetry and EOR measurements were recorded in N2 purged potassium hydroxide and alkaline ethanol solution (1 M), respectively. Chronoamperometry was performed to investigate the stability of the catalysts. The cyclic voltammograms (CV) of the two catalysts compared show minor differences in peak current density, onset potential and by-product tolerance for the alkaline EOR. Further details will be discussed in the poster presentation.The authors acknowledge the financial support by the Austrian Science Fund (FWF): I 3871-N37 and by the Slovenian Research Agency (ARRS) through the Research Funding Programme P1-0175 and Bilateral Research Funding Project N2-0087.[1] B.Cermenek, J.Ranninger, V.Hacker; In Ethanol: Science and Engineering, A.Basile, A.Iulianelli, F.Dalena, N.T.Veziroglu, Eds.; Elsevier Inc.: Amsterdam, 2019, 383-405.[2] B.Cermenek, J.Ranninger, B.Feketeföldi, I.Letofsky-Papst, N.Kienzl, B. Bitschnau, V. Hacker, Nano Research, 2019, 12 (3), 683-693.[3] M. Nosan, M. Löffler, I. Jerman, M. Kolar, I. Katsounaros, and B. Genorio, ACS Appl. Energy Mater. 2021 Figure 1

Electrocatalysts based on low amounts of palladium combined with tin nanoparticles and cerium dioxide nanorods for application as ADEFC anodes

This study demonstrates the structural properties and evaluates the electrocatalytic activity of an ethanol oxidation reaction using ternary materials composed by Pd and Sn nanoparticles combined with CeO2 nanorods (NR) anchored on Vulcan carbon black to be used as an anode in alkaline direct ethanol fuel cells (ADEFCs). The highest open circuit voltage (1010 mV), maximum power (30 mW cm−2) and current densities (113 mA cm−2) were achieved using (Pd1Sn3)10(CeO2 NR)20(Vn)70, while the commercial anode values were 968 mV, 23 mW cm−2 and 123 mA cm−2. Although similar performance for both anodes was observed, the ternary hybrid electrocatalyst contains an 8-fold lower Pd content than the commercial material. This outcome may be justified by the higher defect density presented by the carbon support observed by Raman spectroscopy and the metal oxidation state modifications detected by X-ray photoelectron spectroscopy, as well as the electrochemically active surface area presented by the ternary electrocatalyst. The combination of higher vacancies, defects and oxygenated species in the carbon support and the synergistic effect between the oxyphilic Sn and CeO2 NR species and the Pd nanoparticles results in an electrochemical performance that makes these ternary electrocatalysts promising anode materials for ADEFC applications.

Fast and Inexpensive Synthesis of Multilayer Graphene Used as Pd Support in Alkaline Direct Ethanol Fuel Cell Anode

Fast and Inexpensive Synthesis of Multilayer Graphene Used as Pd Support in Alkaline Direct Ethanol Fuel Cell Anode

Poly(vinyl alcohol)-Based Anion Exchange Membranes for Alkaline Direct Ethanol Fuel Cells

Crosslinked anion exchange membranes (AEMs) made from poly(vinyl alcohol) (PVA) as a backbone polymer and different approaches to functional group introduction were prepared by means of solution casting with thermal and chemical crosslinking. Membrane characterization was performed by SEM, FTIR, and thermogravimetric analyses. The performance of AEMs was evaluated by water uptake, swelling degree, ion exchange capacity, OH- conductivity, and single cell tests. A combination of quaternized ammonium poly(vinyl alcohol) (QPVA) and poly(diallyldimethylammonium chloride) (PDDMAC) showed the highest conductivity, water uptake, and swelling among other functional group sources. The AEM with a combined mass ratio of QPVA and PDDMAC of 1:0.5 (QPV/PDD0.5) has the highest hydroxide conductivity of 54.46 mS cm-1. The single fuel cell tests with QPV/PDD0.5 membrane yield the maximum power density and current density of 8.6 mW cm-2 and 47.6 mA cm-2 at 57 °C. This study demonstrates that PVA-based AEMs have the potential for alkaline direct ethanol fuel cells (ADEFCs) application.

Effect of alkali doping on alkaline stability and cell performance of quaternization polyvinyl alcohol/graphene oxide membranes for passive DEFCs

Alkaline stability of anion exchange membrane (AEM) is a crucial property to produce an effective performance in alkaline passive direct ethanol fuel cells (DEFCs). In theory, a high concentration of alkaline will produce high performance in alkaline DEFCs. However, producing high alkaline stability of AEM is very hard due to the degradation phenomenon of the functional group within the polymeric structure. In this study, Quaternized polyvinyl alcohol/graphene oxide (QPVA/GO) membrane is utilized for alkaline stability evaluation. The resulting QPVA/GO membrane with 15 wt% of GO loading presented a good characterization with excellent alkaline stability and performed well in passive DEFCs. A maximum power density with 4 M of alkaline doped QPVA/GO membrane was obtained 16.88 mW cm−2 and successfully sustained the durability test in 1000 h at ambient condition. Thus, these membrane properties are promising for an alkaline system of fuel cells.

Molybdenum compound cocatalyzed Ni‐based anode electrocatalysts for EOR in alkaline media

In this study, Mo2C and MoS2 were used as cocatalyst for a non-noble metal for the first time for ethanol electro-oxidation reaction (EOR) in alkaline media. Anode electrocatalysts containing Nickel, Mo compound, and carbon support were synthesized at different weight ratios of Ni and Mo2C (or MoS2) while keeping the carbon support weight constant in each catalyst combination to investigate the best weight ratio among our range. Physical characterizations of the electrocatalysts were investigated by XRD, XPS, SEM-EDS, EDAX, and TEM techniques. Electrochemical performance of the catalysts was studied via cyclic voltammetry (CV), linear sweep voltammetry (LSV), and chronoamperometry (CA) by using a home-made electrochemical cell test system exhibiting similar alkaline direct ethanol fuel cell (ADEFC) architecture by giving the opportunity of using an anion exchange membrane. All of the Ni-Mo2C/C and Ni-MoS2/C at different weight ratios were shown better performance than pristine Ni and Ni/C. The highest current density was measured with Ni-Mo2C/C-2 (11.4 mA cm−2) anode catalyst, which exhibits the highest electrochemical reaction rate. The diffusion coefficient of the catalysts was calculated by using the data from linear LSV. CA experiment results showed that the tolerance for catalytic poisoning and durability of Ni-Mo2C/C-2 was better among all the electrocatalysts. Highlights Literature survey showed that Mo2C and MoS2 are promising co-catalysts for EOR. However, there is a lack of study on the use of Mo2C or MoS2 as co-catalyst with a non-noble metal. Molybdenum compound containing transition metal-based anode electro-catalysts were synthesized for EOR in alkaline media. A home-made electrochemical cell is designed to make the system more similar to an ADEFC system. The results of the electrochemical characterizations are showed that the Mo compound addition increased the catalytic activity and stability.

NaNbO3 microcubes decorated with minimum Pd and maximum performance for Alkaline Direct Ethanol Fuel Cell applications

NaNbO3 microcubes with Pd for application in an Alkaline Direct Ethanol Fuel Cell (ADEFC) anode with high performance and minimal amounts of Pd are investigated herein. The Pd heterostructure on NaNbO3 is evaluated in two different structures NaNbO3–Pd/C and NaNbO3@Pd/C. NaNbO3–Pd/C electrocatalyst presents a less positive Eonset for CO-stripping. The NaNbO3–Pd/C electrocatalyst exhibits lower Pd and Nb mass losses compared to NaNbO3@Pd/C during the 24-h experiment. A single ADEFC experiment has 18 mW cm−2 at 50 and 60 °C using only 0.16 mg cm−2 of Pd for NaNbO3–Pd/C production. This Pd metallic loading is 6-fold lower than that of commercial Pd/C (AA). Experimental evidence indicates that the electronic effect between Pd and Nb and the high EASA are the likely reasons for these findings. Therefore, NaNbO3 microcubes with Pd may be an advantageous electrocatalyst for applications in ADEFC anodes.

Hybrid palladium-ceria nanorod electrocatalysts applications in oxygen reduction and ethanol oxidation reactions in alkaline media

Fossil fuel alternatives are being increasingly studied, and alkaline direct ethanol fuel cells (ADEFC) have acquired importance, as to ethanol is a renewable fuel. In this context, the aims of the present study were to synthesize, characterize and evaluate electrocatalytic activity in oxygen reduction reaction (ORR) and ethanol oxidation reaction (EOR) using hybrid electrocatalysts based on Pd nanoparticles and CeO2 nanorods supported on carbon black for application in ADEFC. The highest OCV, maximum current and power densities obtained using Pd15(CeO2 NR)10(Vn)75 as the cathode and Pd10(CeO2 NR)20(Vn)70 as the anode were 1270 mV, 190 mA cm−2 and 65 mW cm−2, respectively. These interesting results are justified by the highest ID/IG ratio and ECSA, which suggest a high number of oxygenated species, defects and vacancies in these electrocatalysts and by the synergistic effect between CeO2 NR and Pd nanoparticles. Therefore, these hybrid electrocatalysts are promising for ADEFC applications.