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PtRh/C–ITO electrocatalysts were prepared in a single-step method using H2PtCl6·6H2O and RhCl3·xH2O as metal sources, sodium borohydride as the reducing agent and a physical mixture of 85% Vulcan Carbon XC72 and 15% In2O3·SnO2 (indium tin oxide—ITO) as support. PtRh/C–ITO were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), cyclic voltammetry, chronoamperommetry, attenuated total reflectance, Fourier transform infrared spectroscopy and performance test on direct alkaline ethanol fuel cell. X-ray diffraction patterns for all PtRh/C–ITO indicated a shift in Pt (fcc) peaks, showing that Rh was incorporated into Pt lattice. Transmission electron microscopy for PtRh/C–ITO showed nanoparticles homogeneously distributed over the support with particles size between 3.0 and 4.0 nm. The XPS results for Pt70Rh30/C–ITO showed the presence of mixed oxidation states of Sn0 and SnO2 that could favor the oxidation of adsorbed intermediates by bifunctional mechanism. Pt90Rh10/C–ITO was more active in electrochemical studies, which could be associated with the C–C bond break. Experiments in direct alkaline ethanol fuel cells showed that the power density values obtained for Pt70Rh30/C–ITO and Pt90Rh10/C–ITO were higher than Pt/C, indicating the beneficial effect of Rh addition to Pt and the use of C–ITO support.

Direct ethanol fuel cell is a promising low temperature fuel cell, but its development is hindered by sluggish kinetics of anode catalysts for ethanol oxidation. Here a high efficient platinum/tin oxide/Graphene nanocomposite is synthesized through a facile and environmentally benign method. The structure and morphology are carefully characterized by X-ray diffraction and Transmission electron microscopy, showing a clear platinum/tin oxide heterostructure uniformly dispersed on graphene support. This catalyst demonstrates the highest activity among the reported catalysts and much higher durability towards ethanol oxidation compared to conventional platinum nanocatalysts. The ultrahigh activity originates from promoted removal of poisoning carbon monoxide immediate species on platinum due to a strong electronic donating effect from both tin oxide and graphene, which is fully supported by carbon monoxide stripping and X-ray photoelectron spectroscopy analysis. Our platinum/tin oxide/Graphene appears to be a promising candidate for ethanol oxidation electrocatalysts.

Direct ethanol fuel cells (DEFCs) are devices for clean and sustainable energy production, where the generation of electrical energy occurs as a result of the anodic ethanol oxidation reaction (EOR). One of the main challenges of these devices is the development of cost-effective and sustainable anodic catalysts, minimizing the use of noble metals such as Pd. In this sense, biomass-derived carbon-supported core–shell nanoparticles of PdNi-based electrocatalyst are of great interest for EOR and its application in DEFCs. The purpose of this work was to demonstrate the possibility of synthesizing a core–shell Ni@Pd electrocatalysts via hydrothermal method, in a fast, simple and environmental friendly way. A biomass hydrothermal liquefaction method using nickel and palladium salts was used to synthesize a biocarbon-supported nickel/palladium core–shell electrocatalyst (Ni@Pd/aHC). The electrocatalyst was morphological and chemical characterized in order to confirm the core–shell particle formation. The electrochemical characterization showed that the Ni@Pd/aHC sample has good electrocatalytic behaviour and good stability over time. The EOR mechanism on the sample and their influence in the faradaic efficiency of a cell were also studied by spectroelectrochemical analysis.

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/Ti0.8W0.2O2 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/Ti0.8W0.2O2 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/Ti0.8W0.2O2 electrocatalyst resulted in much lower onset potential, higher If/Ib value, and superior stability toward EOR, which can be ascribed to the synergistic effect between Pt nanocatalyst and the Ti0.8W0.2O2 catalyst support. Therefore, these findings imply that 18.5 wt % Pt/Ti0.8W0.2O2 is a promising anodic electrocatalyst and possesses the ability to replace Pt/C electrocatalysts in the future.

Made available in DSpace on 2020-12-12T00:55:28Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-11-05 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Fundação de Amparo à Pesquisa do Estado de Goiás Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Laboratório Nacional de Luz Síncrotron Carbon-supported platinum-tin electrocatalysts (Pt–Sn/C) are known to be the most efficient fuel cell anode material to oxidize ethanol in the so-called Direct Ethanol Fuel Cells (DEFC). However, the platinum-tin binary system presents distinct phases depending on the amount of Sn (i.e., the Pt:Sn ratio) and on the thermal annealing temperatures, as well as the presence of oxides (e.g. SnO2) whose influence on the performance of DEFCs is not well understood. In this work, Pt–Sn catalysts presenting distinct Pt:Sn ratios were prepared, characterized and tested in a single DEFC. The combined results from DEFC tests and structural characterization techniques showed that increasing the amount of Sn dissolved into the Pt structure enhances DEFC performance but also that Sn content alone does not explain the overall behavior. Microstructural effects on the DEFC response was further investigated by performing a comprehensive study using high intensity X-ray Diffraction and in situ–X-Ray Absorption Spectroscopy provided by synchrotron light on Pt3Sn1/C samples subjected to thermal treatments in a reducing H2 atmosphere at temperatures of 100, 200, 300, 400, and 500 °C. The results showed that best DEFC performance depends on a balance between the amount of Sn dissolved in Pt, the formation of a new phase (PtSn) and also on the presence of tin oxides, yielding a material with an optimized modified 5d-band electronic structure, which was obtained with a thermal treatment at 200 °C. Universidade Federal de Goiás Instituto de Química, Avenida Esperança s/n Pontifícia Universidade Católica de Goiás, Avenida Universitária 1440 Universidade Federal de São Carlos Departamento de Engenharia Química, Rod. Washington Luís, km 235 Sao Paulo State University (Unesp) School of Engineering, Av Dr. Ariberto Pereira da Cunha, 333 Universidade de São Paulo Instituto de Química de São Carlos C.P. 780 Sao Paulo State University (Unesp) School of Engineering, Av Dr. Ariberto Pereira da Cunha, 333 FAPESP: 2009/07629-6 Fundação de Amparo à Pesquisa do Estado de Goiás: 201201270750433 CNPq: 475609/2008-5 CNPq: 554569/2010-8

Currently, designing and preparing low-cost and high-efficiency electrocatalysts still remains of huge impediment for direct ethanol fuel cells (DEFCs). In this work, by leveraging the unique superiority of Co3[Co(CN)6]2 (Prussian blue analogues, PBA) precursor, we used Pt4+ to replace partial dispersed Co2+ in Co3[Co(CN)6]2 and a metal–organic framework (MOF) derived PtCo electrocatalyst (MD-PtCo/C) was successfully fabricated. Notably, as-obtained MD-PtCo/C (Pt, 0.9532 wt.%) electrocatalyst achieves high utilization rate of ultra-low Pt load and exhibits favorable electrocatalytic performance with lower onset potential, higher EOR activity, less activation energy (Ea) value and better stability compared to commercial Pt/C for ethanol oxidation reaction (EOR). Moreover, the consequence of concentrations (KOH, C2H5OH) and temperatures on electrocatalytic activity of EOR have also been studied. This study would be supportive of developing highly active and low-cost electrocatalysts for other catalytic applications.

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.

Pd-based nanoparticles are considered as the most promising electrocatalysts for ethanol oxidation reaction (EOR) in alkaline direct ethanol fuel cells (DEFCs). However, the existing catalysts stil...

[EN] The preparation polyelectrolytes based on crosslinked poly(vinyl alcohol) (PVA) and chitosan (CS) was considered as a feasible alternative to develop highly functionalised, cost-effective and eco-friendly membranes for proton exchange fuel cell technologies. CS/PVA-based membranes were combined with sulfosuccinic acid (SSA) as crosslinking and sulfonating agent, and glycerol (GL) to promote flexibility and favour their manageability. The chemical structure, the thermo-oxidative behaviour, the ethanol uptake, the electric, the proton conductivity, and the performance in direct ethanol fuel cell (DEFC) were assessed. In general, all the CS/PVA-based polyelectrolytes showed a synergetic increase of thermo-oxidative stability, appropriate absorption and diffusion of ethanol and good proton conductivity, suitable for the typical service conditions of fuel cells. The GL in the membranes reacted with SSA, reduced the ethanol absorption, diffusion coefficient and proton conductivity, but acted as a plasticiser that increased the ductile manageability of the polyelectrolytes to be mounted on the membrane-electrode assembly (MEA). Higher presence of CS and higher the proportion of GL in the polyelectrolyte, improved the material performance in the DEFC. In particular, the crosslinked polyelectrolyte 40CS/PVA/SSA/20GLwith a 40 %wt. of CS referred to PVA, and a 20 %wt. of GL referred to CS, showed a suitable behaviour in the DEFC test, with a maximum value of power density of 746 mW·cm-2., The Spanish Ministry of Economy, Industry and Competitiveness is acknowledged for the projects ENE2017-86711-C3-1-R and UPOV13-3E-1947. The Spanish Ministry of Education, Culture and Sports is thanked for the pre-doctoral FPU grant for O. Gil-Castell (FPU13/01916)

Gold (Au) is a noble metal that has been widely researched due to its high catalytic performance-to-cost ratio. The catalysis could be improved by fabrication of nanostructured arrays on Au thin film with a large area. In the present paper, a facile NSL-RIE approach comprising of nanosphere lithography followed by oxygen plasma reactive ion etching has been developed to fabricate ordered Au nano-ring arrays with almost 100% substrate coverage. The preferential etching of {1 1 1} lattice planes of Au gives rise to the formation of a number of Au nano-pyramids across the entire surface of the nano-ring arrays. The sharp tips along with the Au atoms around the edges of these nano-pyramids provide active sites that perform strong catalysis. Meanwhile, Moire fringes are observed over the etched Au surface which is caused by the rotation of the partial Au lattice with respect to the original Au lattice. This lattice distortion provides high surface energy allowing the significant improvement of the catalysis of Au nano-ring arrays. The direct evidence is proven by the enhanced electrochemical properties of the as-produced Au nano-ring array, which has high efficiency in ethanol oxidation reactions (EORs) with low energy input requirement. Electrochemical testing with varying physical parameters shows that the detecting limit of ethanol is ∼5.0 mM and strong signals come with high concentrations of mobile charge carriers at extreme pH values. Long continuous CV scans reveal that in alkaline medium, C1 pathway could become increasingly preferential over C2 pathway, and thus making the Au nano-ring array structure useful in the field of direct ethanol fuel cell.

Direct ethanol fuel cell technology suffers from a lack of effective anode catalysts for complete ethanol oxidation reaction (EOR). Pd and Pd-based catalysts showed some promise, but only a trace a...

CuPt nano alloy-particles were successfully synthesized by a combination of the methods of bipolar electrolytic and galvanic replacement. Cu2O nanoparticles prepared by a bipolar electrolytic method were used as the sacrificial templates for galvanic replacement reactions with H2PtCl6 solutions. The size of Cu2O nanoparticles was optimized by changing the electrolytic parameters to obtain fine nanoparticles. SEM and TEM analyses showed that Cu2O nanoparticles were grown in a crystal shape with a grain size of about 100 nm. The XRD results indicated that Cu2O nanoparticles were grown in a face-centered cubic structured crystal. The effects of the amount of H2PtCl6 solution on the structure, morphology, composition and electrocatalysis of CuPt were investigated. The phase analysis by XRD showed the presence of CuPt crystalline phases with a rhomb-centered structure. The SEM images indicated that the crystalline shape of Cu2O was turned into a spherical shape with the size expanded to 140 nm after galvanic reaction. The absorption analysis showed that there was one absorption peak at a wavelength of 500 nm for Cu2O while no absorption peak was observed for CuPt alloys. Additionally, compositional analysis by EDX showed that the main components of the alloys were Cu and Pt. The presence of O on the samples indicated that the galvanic reactions were not complete. The cyclic voltammetry measurement showed that CuPt nano alloy-particles exhibit better ethanol oxidation in an alkali medium compared with bare Pt.

Pt-SnO2 catalysts supported on modified carbon fibers were prepared by an electrospinning method with polyacrylonitrile (PAN) as the carrier and polyvinylidene fluoride (PVDF) as the pore-forming agent. The physical-chemical property and catalytic performance of the as-synthesized composites were characterized by XRD, SEM, BET, Chronoamperometry and AC impedance. The results showed that the porous structure in the carbon fibers was formed after calcination at 800 °C in the presence of PVDF. When the weight ratio of PAN/PVDF was 1:0.8, the porous carbon fibers had the largest surface area of 374.85 m2 g−1, which was 3.3 times of carbon fibers prepared without PVDF. The in-situ formed porous structure in carbon fibers can provide more active sites for the catalytic reaction. Therefore, the porous carbon fiber supported Pt-SnO2 catalysts exhibited the best catalytic performance with the ethanol oxidation peak current value of 140.14 mA cm−2 and the electrochemical active area up to 54.296 m2 g−1. DEFC performance showed that the best potential was 0.7 V and the maximum of power density was 18.1 mW cm−2 when the oxygen flow rate and the temperature were 100 mL min−1 and 80 °C, respectively.

In this work, we introduce a novel ZnTe/quinhydrone (ZnTe/QH) nanocomposite as an excellent catalyst for electro-oxidation of ethanol in alkaline medium. The ZnTe semiconductor nanorods were synthesized by a novel chemical route. The synthesized product was characterized by field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), FT-IR spectroscopy, and cyclic voltammetry techniques. Then, this product along with quinhydrone were used for the electrocatalytic oxidation of ethanol in alkaline medium. The ZnTe/QH/GCE showed a higher electrocatalytic activity toward ethanol oxidation. The performance of catalyst was evaluated by electrochemical measurements such as cyclic voltammetry and electrochemical impedance spectroscopy using the three-electrode system. Furthermore, the ZnTe/QH/GCE displayed a higher stability with 93% retention of the initial current density after 6000 s in long term current-time curve. This newly prepared ZnTe/QH nanohybrid could be a promising anodic catalyst for the direct ethanol fuel cells (DEFCs) application.

Direct ethanol fuel cells are a promising technology for clean energy production. The ethanol oxidation reaction (EOR) is surface sensitive and, hence, the study of single-crystal electrodes provides fundamental knowledge of the different activity of the metal crystal planes. However, for practical applications, metal nanoparticles dispersed on a porous support are generally used to enhance the efficiency and to reduce the catalyst cost. Although some research has been devoted to the development of shape-controlled nanoparticles, the finding of an efficient, cost-effective, and easily scaled-up catalytic system remains a challenge. Furthermore, the use of a suitable support with a well-defined nanoarchitecture is essential for the control of the catalyst reactivity. In this Review, a general overview of the performance of single-crystal electrodes and unsupported/supported shape-controlled nanoparticles for the EOR is presented, paying special attention to Pt surfaces. Finally, the major challenges and directions for future research are also discussed to guide the design of efficient shape-controlled catalysts for the EOR.

Microfluidic direct ethanol fuel cells are a promising technology for powering electronic portable devices in the future, and the use of efficient electrocatalysts, both anodic and cathodic are crucial for the development of this type of fuel cells. In this work, an Ag-Pt ethanol-tolerant cathode, synthesized by pulsed laser deposition is studied in the presence of high concentration of ethanol. The cathode exhibited similar catalytic activity to Pt towards the oxygen reduction reaction, performing the reaction through a 4 e− pathway but it showed practically no activity towards the ethanol oxidation reaction. Furthermore, the cathode was successfully tested in a microfluidic direct ethanol fuel cell under mixed-reactant conditions, delivering a maximum cell voltage of 0.75 V and maximum power density of 10 mW cm−2, thus demonstrating its capability to selectively accomplish the oxygen reduction reaction in presence of ethanol concentration as high as 2 M.

Direct ethanol fuel cells (DEFCs) are promising power sources for portable electric devices owing to their high energy conversion efficiency and easy transportation of fuels. However, most electrocatalysts for DEFCs suffer from serious CO poisoning and low selectivity toward the C–C bond cleavage. Herein, we report a class of subnanometer platinum–rhodium nanowires (Pt–Rh NWs) as highly efficient electrocatalysts toward ethanol oxidation reaction (EOR). The prepared PtRh NWs have ultrathin features with an average diameter of only 1.2 nm, largely promoting Pt utilization efficiency. Combining the structural effect and synergistic effect, the optimized PtRh NWs/C shows nearly three times enhancement in activity and promoted stability for EOR compared with commercial Pt/C. Detailed mechanism studies reveal that the introduction of Rh can evidently improve the antipoisoning ability, and the PtRh NWs/C shows enhanced C–C bond cleavage ability with significant C1 pathway selectivity, all of which collectively ...

This paper presents an analytical solution to calculate the mole fraction of the major species involved in the oxidation of ethanol on the anode side, and the reduction of oxygen on the cathode side of a direct ethanol full cell. The equations of the species are solved using two mathematical tools: Separation of variables and Laplace transform. The solutions obtained with the two methods are equivalent and describe the mole fraction of chemical species. The results obtained with the analytical solution were compared with the data obtained with the two-dimensional model, solved numerically with the finite difference method in space and Runge-Kutta method in time. The results of mole fraction of the species obtained through the analytical solution are used to calculate, at a lower cost, the overpotential losses and the direct ethanol fuel cell voltage. The results obtained are in accordance with the experimental data found in the literature for the catalysts Pt-Re-Sn/t-MWCNTs and Pt-Re-Sn/MCN.

The electrocatalysts with superior activity and stability for ethanol oxidation reaction (EOR) are of critical importance for the development of direct ethanol fuel cells (DEFCs). Herein, an effective multistep wet-chemical method has been developed to controllably synthesize hollow echinus-like shaped Pd-based trimetallic nanospheres (Au@PdAgNSs) and corresponding reduced graphene oxide supported Au@PdAgNSs nanocomposite (Au@PdAgNSs/rGO). The results of various physical characterizations indicate that the as-prepared Au@PdAgNSs is a porous and hollow echinus-shaped core-shell structure with gold as the core and PdAg alloy as the shell. Through the CA and CV measurements the resultant Au@PdAgNSs/rGO demonstrated excellent electrocatalytic activity and stability towards ethanol oxidation in an alkaline medium as compared to a commercial Pd/C catalyst, making it very attractive for application in alkaline DEFCs.

Carbon dioxide (CO2) is considered a useful greenhouse gas that can be captured and be used in the electro-syntheses of useful chemicals or fuels. On the other hand, there’s also a tremendous interest on ethanol beneficiation as it is largely produced from crops, and it is regarded as a potential candidate for low temperature fuel cell applications. Although ethanol possesses good advantages, its resistant to oxidation poses a threat. The main objective of the study is to synthesis bio-inspired metal oxide–support catalyst which will help enhance the activity, efficiency and selectivity of Pd catalyst in CO2 reduction, Fuel cell performance and ethanol oxidation. Here, Pd nanoparticles were supported on NiO/C through a green facile one-step process using pomegranate peel extracts as reducing agent. A series of characterizations were carried out to provide proof for and to quantify the presence of Pd, Ni, O and C in the prepared sample. Microscopic methods confirmed the successful preparation of pure NiO/C and (%5 Pd) Pd-NiO/C, evident by the key elemental components, mixed nanostructures and co-existence of Pd and NiO/C. The resultant Pd-NiO/C nanocatalyst revealed higher activity towards the oxidation of ethanol and that the nanocatalyst is more tolerant to poising by intermediate oxidation species. Enhanced cell performance with current and power densities of 66 mA cm−2 and 26 mW cm−2 relative to the commercial Pd/C were obtained under passive conditions at 1 M ethanol in 1MKOH. In addition, the nanocatalyst showed good selectivity to HCOOH with enhanced current efficiencies of 45%.

The low performance and low catalyst utilization of electrodes have been challenging issues for anion-exchange membrane direct liquid fuel cells (AEM DLFCs). Herein, a high-utilization and high-act...

Nano-structured PtCo catalysts and their single metal counterparts were chemically synthesized under ethylene glycol (EG), sodium borohydride (BH) and hydrazine (Hz) reduction scheme. EG reduction was found to be the most effective method for fabricating binary PtCo electro-catalysts that are functionally competent for ethanol oxidation reaction (EOR) in alkaline medium due to enrichment of the electronic properties of the combined matrix through individual contribution of the ad atoms and their oxides. The catalyst matrices were subjected to structural morphology and compositional analysis by the respective techniques like EDX, XRD, TEM and BET isotherm. Performance screening of the entire set of catalysts at room temperature was carried out employing a series of electrochemical techniques involving voltammetry, chronoamperometry, electrochemical impedance spectroscopy. A 50% share of Co in the matrix developed by EG reduction was found to derive superb catalytic output for EOR and exhibit remarkable poison tolerance, driving the reaction toward final product formation.

This review gives an overview of the electrochemical investigations about the properties of various types of graphene composites in the ethanol oxidation. Various routes to provide appropriate graphene-based materials required electrochemical techniques for investigation of different types of the materials as well as their performance and efficacy in ethanol oxidation are discussed in detail. Furthermore, it is demonstrated that the incorporation of suitable materials, e. g. noble metals (graphene-supported binary and ternary metal nanoparticles), metal oxides, conductive polymer, etc, with graphene results in excellent electrocatalytic activity, superb durability and selectivity in ethanol oxidation. Immobilization of electrocatalytically active NPs on graphene supports using physical approaches is considered as an effective route to prepare direct ethanol fuel cell (DEFC) anode catalysts.

Bimetallic Pd/SnO2 nanoparticle electrocatalysts on metal organic framework-derived carbon (MOFDC) were successfully synthesized using microwave-assisted strategies and explored for ethanol oxidation reaction (EOR) in alkaline solution. The materials were thoroughly characterized using XRD, XPS, TEM, and Raman. TEM showed that Pd/SnO2/MOFDC gave the least average particle size of 5.5 nm compared to its counterparts on carbon black (CB). The Pd/SnO2/MOFDC gave the best electrocatalytic performance in terms of high electrochemical active surface area (ECSA) of 962 cm2 mg−1, low onset potential and overpotential for EOR, and high current density (j) of four times more than those of the Pd/CB electrocatalyst. In addition, Pd/SnO2/MOFDC showed superior kinetic parameter (in terms of the Tafel slope (b) = 216.1 ± 8 mV dec−1) and least combined resistance (R = Rs + Rct). These results show that the Pd/SnO2/MOFDPC nanoparticle electrocatalyst is promising for EOR with improved electrocatalytic properties for application in direct ethanol fuel cell (DEFC).

In this paper, a fast and effective method for the palladium (Pd) wire nanostructures synthesis with the great surface area through galvanic replacement reaction utilizing copper nanowires (CuNWS) as a template by the assistance of ultrasound under room temperature condition is proposed. A multifunctional catalyst with the mentioned nanostructure, Pd@CuNWs, and multi walled carbon nanotubes (MWCNTs) and chitosan (CH) as a binder was fabricated. To investigate the morphology and bulk composition of the prepared catalyst, Field Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive X-ray Spectroscopy (EDS), X-ray Powder Diffraction (XRD), and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) were utilized. Various electrochemical techniques including chronoamperometry and cyclic voltammetry were employed for the electrocatalytic activity of ethanol electrooxidation and durability in basic solution. Electrochemical catalytic activity and durability evaluation results proved that the as-synthesized Pd@CuNWs/MWCNTs-CH has a super electrocatalytic activity compared to Pd/MWCNTs and Pd/C electrocatalysts for ethanol electrooxidation. Pd@CuNWs/MWCNTs-CH catalyst demonstrated substantially enhanced performance and long-term stability for ethanol electrooxidation in the basic solution in comparison to Pd/MWCNTs and commercial Pd/C demonstrated the potential in utilizing Pd@CuNWs/MWCNTs-CH as an efficient catalyst for ethanol oxidation. Additionally, thermodynamic and kinetic evaluations revealed that the Pd@CuNWs/MWCNTs-CH catalyst has lower activation energy compared to Pd/MWCNTs and Pd/C which leads to a lower energy barrier and an excellent charge transfer rate towards ethanol oxidation. Noticeably, the Pd@CuNWs/MWCNTs-CH presented excellent catalytic activities with high peak current density which was 9.5 times more than Pd/C, and more negative onset potential in comparison to Pd/C is acquired for ethanol electrooxidation denoting synergistic effect between CuNWs/MWCNs-CH and Pd. The Pd@CuNWs/MWCNTs-CH can be considered as a valid candidate among available electrocatalysts in direct ethanol fuel cells (DEFCs).

Herein, 1-D carbon nanotubes and 2-D graphene hybrid carbon hetero-structure is employed as the catalyst support material for low temperature fuel cell. Partial unraveling of carbon nanotubes results in 1D-2D hybrid hetero-structure with enhanced surface area, while the intact inner tubes result in good electrical conductivity. Platinum-tin alloy decorated on partially exfoliated carbon nanotubes (Pt–Sn/PCNT) were prepared by ethylene glycol reduction method and investigated its electrocatalytic activity towards ethanol oxidation reaction (EOR) for direct ethanol fuel cell (DEFC) and oxygen reduction reaction (ORR) for hydrogen fuelled polymer electrolyte membrane fuel cell (PEMFC). Along with the intrinsic properties of carbon nanotubes, PCNT provides more anchoring sites, thereby facilitates complete utilization of catalysts. The electrochemical EOR studies reveal that Pt–Sn/PCNT has better tolerance to the accumulation of intermediate species than Pt–Sn/CNT. Besides, as-synthesized electrocatalysts exhibit good ORR activity with four-electron pathway. The enhanced EOR and ORR activity of as prepared electrocatalysts is attributed to the high dispersion of catalyst nanoparticles on PCNT along with the inhibition of production of intermediate species on the Pt surface by alloying. Further, the practical suitability of PCNT supported Pt–Sn nanocatalysts as EOR and ORR electrocatalysts has been examined by performing the full fuel cell measurements.

In this study, a non-enzymatic and low-cost method was presented for fuel cell applications in alkaline medium based on the utilization of nickel oxide micro/nanoparticles (NiOMNPs) for carbon-based anode fabrication. NiOMNPs were synthesized through a practical strategy, namely, wet chemical precipitation method. Due to the fact that NiOMNPs can catalyze the oxidation reactions of various organic compounds in alkaline medium, the performance of NiOMNPs decorated carbon paste electrode (CPE) was examined using cyclic voltammetry to select the most appropriate fuel to construct the fuel cell. After the optimization of NiOMNPs amount on CPE, electrocatalytic behavior of NiOMNPs/CPE in alkaline medium was investigated for the ethanol oxidation reaction. Two-compartment ethanol fuel cell using a salt bridge was fabricated to calculate power density and current density values. The results showed that NiOMNPs/CPE could be an alternative to the anodes utilized in enzymatic and microbial fuel cells.

The rational design of highly efficient catalysts for ethanol electrooxidation is extremely challenging for developing direct ethanol fuel cells (DEFCs). Herein, a facile one-pot method has been developed to prepare blackberry-like PdAuCu nanoparticles (NPs) with tunable composition and surface structures. Among PdAuCu NPs with different Pd contents (1.6–22 mass%), PdAuCu NPs-0.5 (contained Pd at 2.5 mass%) delivered one of the highest catalytic activities of Pd-based catalysts towards ethanol electrooxidation, exhibiting a mass activity of 23.0 A mgPd−1. Kinetic analysis, electrochemical impedance spectroscopy and CO stripping test results suggested that the excellent electrocatalytic activity may originate from the optimized balance between Pd content and surface structure of PdAuCu NPs-0.5. The optimization of the balance between composition and surface structure would contribute to the further design of multimetallic nanoparticles for fuel cells and other applications.

The major hindrance for a successful commercialization of direct ethanol fuel cells (DEFCs) is the sluggish ethanol oxidation reaction (EOR) and the rapid poisoning of anodic catalysts by by-products. In this work, a high-performance PdNi nanowire (PdNi-NWs) catalyst was prepared via a two-step process in polyol medium based on the galvanic replacement reaction. By carefully screening parameters for a uniform deposition of Pd layers on Ni nanowires, the PdNi-NWs electrode exhibits a significant enhancement of both catalytic activity and durability for the EOR in alkaline media, which may be ascribed to the electronic structure modification and bifunctional electrocatalytic mechanism with hydroxyl and ethanol bindings on Ni and Pd, respectively. Moreover, these nanowire structures are efficient electron and mass transfer and enriched with abundant active sites by oxygen-rich compounds of Ni. The highest electrocatalytic performance has achieved with a low Pd:Ni molar ratio of 18:100, which reaches 9.3 times superior mass activity and the EOR onset potential shifts 50 mV negatively compared with Pd nanoparticles (PdNPs). These results highlight the active role of PdNi-NWs catalysts in DEFCs.

Made available in DSpace on 2021-06-25T11:12:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-04-06 The advancement of direct ethanol fuel cell (DEFC) represents a real challenge to electrochemical science because ethanol changes significantly the triple phase boundary properties such as the redox reactions and the proton transport. Ethanol molecules promote poor fuel cell performance due to their slow oxidation rate, reduction of the proton transport due to high affinity of ethanol by the membrane, and due to mixed potential when the ethanol molecules reach the cathode by crossover. DEFC performance has been improved by advances in the membranes, e.g., low ethanol crossover polymer composites, or electrode materials, e.g., binary/ternary catalysts. Herein, high temperature (130 °C) DEFC tests were systematically investigated by using optimized electrode and electrolyte materials: Nafion-SiO2 hybrid electrolyte and well-alloyed PtSn/C electrocatalyst. By optimizing both the electrode and the electrolyte in conjunction, DEFCs operating at 130 °C exhibited a threefold increase on performance as compared to standard commercially available materials. Instituto de Pesquisas Energéticas e Nucleares IPEN/CNEN-SP, Av. Prof. Lineu Prestes, 2242 Instituto de Química Universidade Estadual Paulista UNESP, Rua Prof. Francisco Degni, 55 Instituto de Química Universidade Estadual Paulista UNESP, Rua Prof. Francisco Degni, 55

The human craving for energy is continually mounting and becoming progressively difficult to gratify. At present, the world's massive energy demands are chiefly encountered by nonrenewable and benign fossil fuels. However, the development of dynamic energy cradles for a gradually thriving world to lessen fossil fuel reserve depletion and environmental concerns is currently a persistent issue for society. The discovery of copious nonconventional resources to fill the gap between energy requirements and supply is the extreme obligation of the modern era. A new emergent, clean, and robust alternative to fossil fuels is the fuel cell. Among the different types of fuel cells, the direct ethanol fuel cell (DEFCs) is an outstanding option for light-duty vehicles and portable devices. A critical tactic for obtaining sustainable energy sources is the production of highly proficient, economical and green catalysts for energy storage and conversion devices. To date, a broad range of research is available for using Pt and modified Pt-based electrocatalysts to augment the C2H5OH oxidation process. Pt-based nanocubes, nanorods, nanoflowers, and the hybrids of Pt with metal oxides such as Fe2O3, TiO2, SnO2, MnO, Cu2O, and ZnO, and with conducting polymers are extensively utilized in both acidic and basic media. Moreover, Pd-based materials, transition metal-based materials, as well as transition metal-based materials are also points of interest for researchers nowadays. This review article delivers a broad vision of the current progress of the EOR process concerning noble metals and transition metals-based materials.

An overview is reported about the history of prevailing direct ethanol fuel cells (DEFCs) as a renewable green source of energy. Important features of the effect of: (1) operating DEFCs in alkaline media, (2) development of a suitable preparation method or technique of the catalyst to achieve more favorable dispersion and smaller particle size, (3) employing high surface area supports, (4) combining the catalyst with another metal, metal oxide, metal carbide or nitride, (5) addition of additives in the coating bath; on electrocatalytic performance of DEFCs are discussed.

In this study, a highly efficient carbon-supported Pd catalyst for the direct ethanol fuel cell was developed by electrodepositing nanostructured Pd on oxygen plasma-treated carbon fiber paper (Pd/pCFP). The oxygen plasma treatment has been shown to effectively remove the surface organic contaminants and add oxygen species onto the CFP to facilitate the deposition of nano-structured Pd on the surface of carbon fibers. Under the optimized and controllable electrodeposition method, nanostructured Pd of ~10 nm can be easily and evenly deposited onto the CFP. The prepared Pd/pCFP electrode exhibited an extraordinarily high electrocatalytic activity towards ethanol oxidation, with a current density of 222.8 mA mg−1 Pd. Interestingly, the electrode also exhibited a high tolerance to poisoning species and long-term stability, with a high ratio of the forward anodic peak current density to the backward anodic peak current density. These results suggest that the Pd/pCFP catalyst may be a promising anodic material for the development of highly efficient direct alcohol fuel cells.

One-dimensional (1D) metal-coated Pd structures are efficient catalysts for the ethanol electro-oxidation and promising strategy for minimizing the Pd-loading toward commercialization of direct ethanol fuel cells (DEFCs). Herein, the decorated and core-shell architectures of a novel Pd coating on Ag nanowires (PdAg-NWs) are controllable by a two-step polyol method based on the galvanic replacement reaction. The integration of uniform shell with a low Pd concentration and partial hollow structure onto 1D PdAg-NWs exhibits the highest efficiency for ethanol oxidation reaction (EOR) in alkaline solution. In comparison with Pd nanoparticles (PdNPs/C), the PdAgNWs/C performes 11 times superior EOR activity, and the onset potential shifts 80 mV negatively. The presence of Ag in PdAg-NWs enhances the absorption capacity of ethanol molecules and hydroxyl ions on the active sites, and improves the catalyst tolerance to CO-like intermediates, making them a potential anodic catalyst for DEFCs.

The high cost of Pt-based electrode materials limits the commercialization of fuel cells and their subsequent application in renewable energy production. It is thus necessary to develop economical, high-performance electrodes alongside biofuels to reduce the pollution associated with the production of energy. Tin dioxide–copper foil (SnO2–Cu) electrode materials are herein developed using an electrodeposition process. Cyclic voltammetry, chronoamperometry, and potentiodynamic polarization methods are used to electrochemically characterize the electrode materials, with the results revealing that their excellent catalytic properties result in them delivering a high current. The surface morphologies of the developed electrodes are examined using scanning electron microscopy, with the results showing that upon an increase in the deposition time, a finer deposit of SnO2 is formed on the surface of the Cu foil. Consequently, electrochemical oxidation using an enhanced surface area of the material leads to it exhibiting a high current and excellent corrosion resistance. Powder X-ray diffraction was used to confirm the successful depositing of SnO2 on the surface of Cu. The fuel cell fabricated using the SnO2–Cu electrode is promising for use in clean energy generation, as it can be prepared at low cost compared to conventionally used electrodes.

Physical and electrochemical properties of Pd catalysts combined with Ru and Mo on carbon support were investigated. To this end, Pd, Pd1.3Ru1.0, Pd3.2Ru1.3Mo1.0 and Pd1.5Ru0.8Mo1.0 were synthesized on Carbon Vulcan XC72 support by the method of thermal decomposition of polymeric precursors and then physically and electrochemically characterized. The highest reaction yields are obtained for Pd3.2Ru1.3Mo1.0/C and Pd1.5Ru0.8Mo1.0/C and, as demonstrated by thermal analysis, they also show the smallest metal/carbon ratio compared the other catalysts. XRD (X-ray Diffraction) and Raman analyses show the presence of PdO and RuO2 for the Pd/C and the Pd1.3Ru1.0/C catalysts, respectively, a fact not observed for the Pd3.2Ru1.3 Mo1.0 /C and the Pd1.5Ru0.8Mo1.0/C catalysts. The catalytic activities were tested for the ethanol oxidation in alkaline medium. Cyclic voltammetry (CV) shows Pd1.3Ru1.0/C exhibiting the highest peak of current density, followed by Pd3.2Ru1.3Mo1.0/C, Pd1.5Ru0.8Mo1.0/C and Pd/C. From, chronoamperometry (CA), it is possible to observe the lowest rate of poisoning for the Pd1.3Ru1.0/C, followed by Pd3.2Ru1.3Mo1.0/C, Pd1.5Ru0.8Mo1.0/C and Pd/C. These results suggested that catalytic activity of the binary and the ternary catalysts are improved in comparison with Pd/C. The presence of RuO2 activated the bifunctional mechanism and improved the catalytic activity in the Pd1.3Ru1.0/C catalyst. The addition of Mo in the catalysts enhanced the catalytic activity by the intrinsic mechanism, suggesting a synergistic effect between metals. In summary, we suggest that it is possible to synthesize ternary PdRuMo catalysts supported on Carbon Vulcan XC72, resulting in materials with lower poisoning rates and lower costs than Pd/C. Graphic abstract

This paper presents research on the effects of common solvents such as n-butyl acetate, isopropanol, and ethanol on the properties and electroactivity of catalyst ink based on PtAl/rGO. The inks prepared by mixing PtAl/rGO catalyst, Nafion solution (5 wt%), and solvent were coated on carbon cloth by the spin coating method. The results obtained showed that ethanol was the most suitable solvent for the preparation of catalyst ink with a volume ratio between catalyst slurry and solvent of 1 : 1 (CI-EtOH (1/1) ink). The surface of the CI-EtOH (1/1) coated electrode was smooth, flat, and even and had no cracks due to the increase of Nafion mobility, resulting in significant improvement in the interaction between Pt particles and ionomer. Moreover, the electrochemical activity of the CI-EtOH (1/1) ink in ethanol electrooxidation reaction, in both acidic and alkaline media, has the highest value, with the forward current density, IF, reaching 1793 mA mgPt−1 and 4751 mA mgPt−1, respectively. In the application in direct ethanol fuel cell (DEFC), the CI-EtOH ink-coated anode also exhibited the highest power density in both PEM-DEFC (with a proton exchange membrane) and AEM-DEFC (with an anion exchange membrane) at 19.10 mW cm−2 and 27.07 mW cm−2, respectively.

The understanding of electrocatalytic activity and poisoning resistance properties of Pt and Pd nanoparticles, recognized as the best electrocatalysts for the ethanol oxidation reaction, is an essential step for the commercialization of direct ethanol fuel cells (DEFCs). In this paper, mono and bimetallic Pt and Pd nanoparticles with different atomic ratios have been synthesized to study their electrocatalytic properties for an ethanol oxidation reaction in alkaline solutions. The different nanoparticles were physiochemically characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The electrochemical characterization was performed by cyclic voltammetry and chronoamperometry measurements. The electrochemical measurements indicate that Pt nanoparticles have much higher electrocatalytic activity for ethanol oxidation than Pd nanoparticles. The studies with bimetallic PtPd nanoparticles showed a significant impact of their composition on the ethanol oxidation. Thus, the highest electrocatalytic activity and poisoning resistance properties were obtained for Pt3Pd2 nanoparticles. Moreover, this study demonstrates that the poisoning of the catalyst surface through ethanol oxidation is related to the prevalence of the acetaldehyde–acetate route and the polymerization of acetaldehyde through aldol condensation in the alkaline media. This research was funded by Ministerio de Ciencia e Innovación (Spain) grant number PID2019-105653GB-100), Generalitat Valenciana (Spain) grant number PROMETEO/2020/063, and the University of Zanjan Research Council.

Direct ethanol fuel cell (DEFC) are promising for portable power source due to ethanol non toxic, renewable and high energy density. DEFC is grouped according to the type of membrane used either acidic and alkaline. In this review, the development of acidic membrane and alkaline membrane of previous literature is presented including the commercial membranes. In addition to that, different types of polymeric and filler including organic and inorganic membrane is discussed. Membrane performance and behavior is determined from it's characterization covering variables such as water uptake, ion exchange capacity, ethanol permeability, conductivity and membrane morphology. Future membrane development is discussed towards to maximized the DEFC performance ,that will enable the technology entering the commercial market.

Ethanol could be considered as a carbon-neutral and sustainable fuel source if it is produced from biomass. Ethanol is promising due to its low cost and low toxicity. There are two different types of direct ethanol fuel cells (DEFCs): alkaline and acidic. Successful results have been reported in the electrooxidation of ethanol with platinum (Pt) catalysts in these fuel cells. Moreover, studies on Palladium (Pd) have also shown very promising results and this seems to be the primary catalyst to replace Pt. Development of a DEFC is an important field that needs to be scientifically studied on its engineering technology as well as electrochemical reactions. However, in order to obtain a commercially available fuel cell, technical problems and economic concerns need to be eliminated. This section includes both types of DEFC and gives insight into future system designs and future trends for DEFCs to achieve commercial and engineering success.

Crosslinked membranes have been synthesized by a casting process using polybenzimidazole (PBI) and poly(vinyl benzyl chloride) (PVBC). The membranes were quaternized with 1,4-diazabicyclo[2.2.2]octane (DABCO) to obtain fixed positive quaternary ammonium groups. XPS analysis has showed insights into the changes from crosslinked to quaternized membranes, demonstrating that the crosslinking reaction and the incorporation of DABCO have occurred, while the 13C-NMR corroborates the reaction of DABCO with PVBC only by one nitrogen atom. Mechanical properties were evaluated, obtaining maximum stress values around 72 MPa and 40 MPa for crosslinked and quaternized membranes, respectively. Resistance to oxidative media was also satisfactory and the membranes were evaluated in single direct ethanol fuel cell. PBI-c-PVBC/OH 1:2 membrane obtained 66 mW cm&minus, 2 peak power density, 25% higher than commercial PBI membranes, using 0.5 bar backpressure of pure O2 in the cathode and 1 mL min&minus, 1 KOH 2M EtOH 2 M aqueous solution in the anode. When the pressure was increased, the best performance was obtained by the same membrane, reaching 70 mW cm&minus, 2 peak power density at 2 bar O2 backpressure. Based on the characterization and single cell performance, PBI-c-PVBC/OH membranes are considered promising candidates as anion exchange electrolytes for direct ethanol fuel cells.

Direct ethanol fuel cells (DEFCs) show a huge potential to power future electric vehicles and portable electronics, but their deployment is currently limited by the unavailability of proper electrocatalysis for the ethanol oxidation reaction (EOR). In this work, we engineer a new electrocatalyst by incorporating phosphorous into a palladium-tin alloy and demonstrate a significant performance improvement toward EOR. We first detail a synthetic method to produce Pd2Sn:P nanocrystals that incorporate 35% of phosphorus. These nanoparticles are supported on carbon black and tested for EOR. Pd2Sn:P/C catalysts exhibit mass current densities up to 5.03 A mgPd−1, well above those of Pd2Sn/C, PdP2/C and Pd/C reference catalysts. Furthermore, a twofold lower Tafel slope and a much longer durability are revealed for the Pd2Sn:P/C catalyst compared with Pd/C. The performance improvement is rationalized with the aid of density functional theory (DFT) calculations considering different phosphorous chemical environments. Depending on its oxidation state, surface phosphorus introduces sites with low energy OH− adsorption and/or strongly influences the electronic structure of palladium and tin to facilitate the oxidation of the acetyl to acetic acid, which is considered the EOR rate limiting step. DFT calculations also points out that the durability improvement of Pd2Sn:P/C catalyst is associated to the promotion of OH adsorption that accelerates the oxidation of intermediate poisoning COads, reactivating the catalyst surface., This work was supported by the European Regional Development Funds and by the Spanish Ministerio de Economía y Competitividad through the project SEHTOP, ENE2016- 77798-C4-3-R, and ENE2017-85087-C3. X. Y. thanks the China Scholarship Council for the scholarship support. J. Liu acknowledges support from the Jiangsu University Foundation (4111510011). J. Li obtained International Postdoctoral Exchange Fellowship Program (Talent-Introduction program) in 2019 and is grateful for the project (2019M663468) funded by the China Postdoctoral Science Foundation. Authors acknowledge funding from Generalitat de Catalunya 2017 SGR 327 and 2017 SGR 1246, and from IST Austria. ICN2 acknowledges the support from the Severo Ochoa Programme (MINECO, grant no. SEV-2017-0706) and is funded by the CERCA Programme/Generalitat de Catalunya. J. Llorca is a Serra Húnter Fellow and is grateful to MICINN/FEDER RTI2018-093996-B-C31, GC 2017 SGR 128 and to ICREA Academia program.

Ethanol is preferred to be oxidized into CO2 for the construction of a high-performance direct ethanol fuel cell since this complete ethanol oxidation reaction (EOR) transfers 12 electrons. However, this EOR is sluggish and has the low activity as well as poor selectivity. To promote such a favorable EOR, more exactly the cleavage selectivity of CC bonds in ethanol, phosphorus-doped silver-core-and-Pd-shell catalysts (denoted as Ag@PdP) are designed and synthesized. In the alkaline media, a Ag@Pd2 P0.2 catalyst is superior toward EOR into CO2 . It exhibits seven times higher mass activity and six times higher selectivity than the benchmark Pd/C catalyst. As confirmed by means of density functional theory calculation and in situ Fourier-transform infrared spectroscopy, such high performance stems from an increased adsorption energy of OH radicals on the Pd active sites. Meanwhile, the tensile strain effect of a core-shell structure of this Ag@Pd2 P0.2 catalyst favors the formation of adsorbed CH3 CO intermediate, the key species for the enhanced C-C cleavage into CO2 , instead of acetate. The proposed way to design and synthesize such high-performance EOR catalysts will explore the practical applications of direct alkaline ethanol fuel cells.

Pt/C, PtMOn/C (M = Ni, Sn, Ti, and PtX/C (X = Rh, Ir) catalyst systems were prepared by using the pulse alternating current (PAC) technique. Physical and electrochemical parameters of samples were carried out by x-ray powder diffraction (XRD), transmission electron microscopy (TEM), and CO stripping. The catalytic activity of the synthesized samples for the ethanol electrooxidation reaction (EOR) was investigated. The XRD patterns of the samples showed the presence of diffraction peaks characteristic for Pt, NiO, SnO2, TiO2, Rh, and Ir. The TEM images indicate that the Pt, Rh, and PtIr (alloys) particles had a uniform distribution over the carbon surface in the Pt/C, PtRh/C, PtIr/C, and PtMOn/C (M = Ni, Sn, Ti) catalysts. The electrochemically active surface area of catalysts was determined by the CO-stripping method. The addition of a second element to Pt or the use of hybrid supported catalysts can evidently improve the EOR activity. A remarkable positive affecting shift of the onset potential for the EOR was observed as follows: PtSnO2/C &gt, PtTiO2/C &asymp, PtIr/C &asymp, PtNiO/C &gt, PtRh/C &asymp, Pt/C. The addition of SnO2 to Pt/C catalyst led to the decrease of the onset potential and to significantly facilitate the EOR. The long-term cyclic stability of the synthesized catalysts was investigated. Thereby, the PtSnO2/C catalyst prepared by the PAC technique can be considered as a promising anode catalyst for direct ethanol fuel cells.

The study focuses on the influence of Ni and Bi on alkaline ethanol oxidation reaction (EOR) activities, stabilities and structure characteristics of carbon supported Pd-based nanocatalysts (Pd/C, Pd60Ni40/C, Pd60Bi40/C, Pd60Ni20Bi20/C) by cyclic voltammetry/chronoamperometry using rotating disk electrode and various physico-chemical methods such as X-ray powder diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy coupled with energy dispersive X-ray spectroscopy and inductively coupled plasma optical emission spectrometry. Nickel generates more adsorbed OH on the Pd catalyst surface than Bi and promotes the oxidation of adsorbed ethanol species. This results in a low onset potential toward ethanol oxidation with high current density. The presence of Bi facilitates high tolerance toward various reaction intermediates resulting from the incomplete ethanol oxidation, but might also initiate the agglomeration of Pd nanoparticles. The novel Pd60Ni20Bi20/C nanocatalyst displays exceptional byproduct tolerance, but only satisfying catalytic activity toward ethanol oxidation in an alkaline medium. Therefore, the EOR performance of the novel carbon supported ternary PdxNiyBiz anode catalyst with various atomic variations (Pd70Ni25Bi5/C, Pd70Ni20Bi10/C, Pd80Ni10Bi10/C and Pd40Ni20Bi40/C) using the common instant reduction synthesis method was further optimized for the alkaline direct ethanol fuel cell. The carbon supported Pd:Ni:Bi nanocatalyst with atomic ratio of 70:20:10 displays outstanding catalytic activity for the alkaline EOR compared to the other PdxNiyBiz/C nanocatalysts as well as to the benchmarks Pd/C, Pd60Ni40/C and Pd60Bi40/C. The synergy and the optimal content in consideration of the oxide species of Pd, Ni and Bi are crucial for the EOR kinetic enhancement in alkaline medium.

Although Pt-based anodes have shown promising electrochemical behaviors toward the ethanol oxidation reaction (EOR) in the direct ethanol fuel cell (DEFC) application, the rational design for optimizing the structures and compositions of catalysts is yet to be fully understood due largely to the lack of mechanistic insights into the catalytic reaction. Herein, we systematically investigated EOR on Pt-based binary (PtSn and PtRu) and ternary (PtSnRu) nanorods with varied atomic ratios to elucidate the effects of chemical composition and structure on the electrochemical behavior. The electrochemical results showed that Sn and Ru in the ternary PtSnRu NRs can effectively promote the EOR performance, both at 0.6 V (I06) and peak potential (Imax), as compared to binary PtSn and PtRu NRs. The enhanced activity at a low potential (I06) corresponded to the strengthened adsorption of water and ethanol on Ru site with a highly energetic d band structure; this at a high potential (Imax) was related to the oxygen-containing species on surface Sn, lowering the oxidation barriers through hydrogen-bond interactions, according to density functional theory-based calculations. The combination of electrochemical experiments on modeled binary and ternary electrodes and theoretical computation offers an effective approach to clarify the complex EOR mechanism and provides information vital to achieving the realistic design of better EOR anodes.

The Pd/C, PdRh(50:50)/C and PdSn(50:50)/C nanomaterials were used as electrocatalysts for ethanol (EtOH) oxidation in Direct Ethanol Fuel Cell (DEFC) in an alkaline medium. This work aims to provide a complete physical characterization of the nanomaterials, elucidate the bifunctional mechanism concerning ethanol oxidation reaction and understand the influence of carbon – metal bonding in the electrochemical activity. These nanomaterials were investigated by X-ray photoelectron spectroscopy (XPS) and revealed that the atomic percentage of the surface is different of those obtained by Energy Dispersive X-ray spectroscopy (EDS). Raman spectroscopy showed a bonding between palladium and carbon atoms which can play a decisive role in the performance of the materials. Attenuated Total Reflectance technique coupled to the Fourier Transform Infrared spectroscopy (ATR-FTIR) made possible to investigate the oxidation products originated by the ethanol oxidation, and all the electrocatalysts showed the presence of acetaldehyde, carbonate ions, acetate and carbon dioxide, suggesting that the mechanism of oxidation is incomplete. Among all the nanomaterials studied, PdSn(50:50)/C showed the best electrochemical and Fuel Cell's results. It is about 33% better than Pd/C. The micrographs obtained by Transmission Electron Microscopy (TEM) revealed some agglomerate regions, but they are consistent with the literature data.

Despite the net energy yield be the primary goal of ethanol electro-oxidation reaction (EOR), it is never measured in fundamental electrochemical studies. By combining galvanodynamic and potentiodynamic profiles of the steady states of the system, we demonstrate a methodology to estimate the dissipation of chemical energy that allows the inference of the fuel cell power output in relative terms. Apart from the empirical energy dissipation, several kinetic information are unravelled: (a) the kinetics is governed by ethanol adsorption rate for both media and for both external control modes; and (b) either the maximum current sustained by EOR or the steady state currents are, in addition, governed by a global coverage of poisonings species, which includes the contributions from COad and non-reactive OHad. The blocking effect of potassium cations over EOR is clearly verified, reducing the maximum activity up to a factor of 0.19, which is interpreted as an effect of the high coverage of non-reactive OHad. Finally, it is expected a slightly improvement of the power output of a direct ethanol fuel cell operating at steady state in alkaline media due to the lower chemical dissipation at fixed interfacial current value. Nonetheless, the blocking effect of potassium in alkaline media may, depending on the concentration, either induces an oscillatory regime at higher overvoltage (above 0.57 V) along with the preservation of the energy generation at lower overvoltage or completely decrease the energy generation due to a drastic loss of energy used to polarize the EOR.