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Activate carbon (AC) demand has increased worldwide, with application in adsorption, heterogeneous catalysis, and most recently as electrocatalyst support. However, while AC production from agro-industrial waste are widely researched, textile waste is neglected as raw material. In this study, cotton fabric was first applied as textile dye adsorbent after iron impregnation, which enhanced the adsorption capacity. The dye adsorbed fabric was than sequentially pyrolyzed at 800 °C for 2 h under N2 atmosphere, producing a magnetic mesoporous activated carbon (MAC) of 472 m2 g-1 BET surface area with 82% micropores and magnetization saturation of 34.2 emu g-1 deriving from encapsulated metallic αFe. This new simple and fast one-step carbonization, activation and iron incorporation method, has very low chemicals consumption and waste generation compared to the traditionally applied ones. The so produced MAC was loaded with 20 % Pd and tested for electrocatalyst properties: high density current for ethanol oxidation of 549 mA mg-1Pd, 1.37 times higher than using commercial Pd catalyst, lower onset potential of -0.48 V vs NHE. Application of the electrocatalyst for direct ethanol fuel cell achieved a high energy production of 27 mW cm-2 at 353 K.

Direct ethanol fuel cell (DEFC) as a promising device for converting chemical energy to electricity has been paid ever-increasing attention. However, the slow kinetics of ethanol electrooxidation at an anode hinders the application of DEFCs. Although Pt is the best catalyst among all the pure metal catalysts, it still has a relatively poor ability to break the C C bond, is deactivated by the accumulated COad intermediates, and undergoes unwanted desired structure change over long-term operation. In recent years, the addition of other metals to form binary, ternary, and quaternary catalysts have significantly improved electroactivity and stability. Ternary catalysts can have numerous element combinations and complicated architectures and, therefore, have been the subject of considerable research. In this review, most of the reported ternary catalysts will be summarized and categorized according to their structure while discussing the essence of the role of each component.

EOR is a semi-reaction of direct ethanol fuel cells (DEFCs), and determines the performance of the DEFCs. Therefore, it is very important for EOR to rationally design an electrocatalyst with excellent activity, stability and CO-resistance. Based on this, we report the synthesis of MOF based composite catalysts by a facile method, which is formed by combining polyaniline hydrogel (PANH) with MOF 1 and carbon cloth (CC). At the same time, the structures of the composites were characterized by XRD, SEM and XPS. Under the optimum conditions, the j value for EOR is 107 mA cm−2 under alkaline conditions at 0.6 V, which indicates that composite 2 has excellent catalytic activity for EOR, and is superior to that of the previously reported nickel-based catalysts for EOR. The Tafel slope and the exchange current density of composite 2 are 88.9 mV dec−1 and 1.95 × 10−5 A cm−2 respectively. In addition, the j value of composite 2 was 65% of the original value after 1000 CV cycles. However, when the electrolyte was changed into the original one (1 M KOH + 1 M EtOH), the j value returned to 74% of the original value. Based on the excellent electrocatalytic performance, good stability and anti-CO poisoning, composite 2 is expected to be an economic, efficient and CO poisoning resistant electrocatalyst for EOR.

Electrocatalytic preparation of Pt-based nanocomposites has been investigated for improvement of direct ethanol fuel cells (DEFCs). In this study, new alternative catalysts of Pt-decorated cerium zirconium oxide-modified multiwalled carbon nanotubes (Pt/CeZrO4/MCNT) were successively prepared to improve the activity of the ethanol oxidation reaction (EOR). The prepared CeZrO4 with a face-centered cubic (fcc) structure compatibly dispersed onto MCNT provides abundant active Pt sites for highly active catalysts. The fcc-structured Pt was also satisfactorily decorated onto CeZrO4/MCNT, resulting in highly active Pt. The Ce4+/Ce3+ redox property can promote oxygen vacancies to improve the electrochemical activity for oxidation of carbonaceous species. An increase in roughness and a stabilized catalyst structure can also be produced by inserting Zr4+ into the ceria metal oxide. The prepared Pt/20%CeZrO4/MCNT catalysts present excellent electrochemical active surface area, mass activity, CO tolerance and high electron kinetic transfer with low resistance and high stability over commercial PtRu/C toward EOR. This promising catalyst material could be introduced to enhance the anodic oxidation reaction in DEFCs.

Of late, fuel cells have drawn great attentions owing to high-energy demands, fossil fuel depletion and worldwide environmental pollution. Direct ethanol fuel cell (DEFC) constituted as one of the most promising sources of green energy, howbeit the ethanol oxidation reaction (EOR) sluggish kinetic is one of the essential challenges toward the commercialization of DEFCs. Herein, we introduce bimetallic catalyst on CoNiO2 modified reduced graphene oxide (rGO) to completely exploit the advantages of nano-surface structures as well as the reduction of Pt and Pd loading in fuel cells. With the combined advantages of PtPd, CoNiO2 and rGO, a significant enhancement in electrocatalytic behavior, stability and CO poisoning tolerance of PtPd have been observed. Regarding the implications, PtPd/CoNiO2/rGO is greatly preferable than Pt/CoNiO2/rGO and Pd/CoNiO2/rGO in terms of high electroactive surface area (ECSA), electro-catalytic activity, and lower onset potential (Eons) towards the EtOH oxidation in alkaline media. Furthermore, the chronoamperometry curve (CA) illustrated 77% after 3600 s which is dramatically soared compared with the other electrodes (≤40%), demonstrating the high stability of the PtPd bimetallic nanoparticle electrocatalyst. Ultimately, PtPd/CoNiO2/rGO nanocomposite is found to be an excellent anode electrocatalyst for application in DEFCs.

Direct Ethanol Fuel Cells (DEFCs) have fascinated remarkable attention on account of their high current density and being environmentally friendly. Developing efficient and durable catalysts with a simple and fast method is a great challenge in the practical applications of DEFCs. To this end, the bimetallic Pd–Ag with adjustable Pd:Ag ratios were synthesized via a simple and one-pot strategy on activated carbon as a support in this study. The Pd–Ag/C catalysts with different molar ratios were synthesized by simultaneous reduction of Pd and Ag ions in the presence of the ethanolic sodium hydroxide as a green reducing agent for the first time. Several different methods, including FE-SEM, HR-TEM, XRD, XPS EDX, ICP-OES, and BET were used to confirm the structure and morphology of the catalysts. The performance of catalysts was also examined in ethanol oxidation. Obtained results of electrochemical experiments revealed that the Pd3–Ag1/C catalyst had superior catalytic activity (2911.98 mAmg−1Pd), durability, and long-stability compared to the other catalysts. The excellent catalytic characteristic can be attributed to the synergistic effect between Pd and Ag. We presume that our simple method have the chance to be utilized as a proper method for the synthesis of fuel cell catalysts.

Improving the catalytic activity and durability of the ethanol oxidation reaction (EOR) is crucial for realizing the commercialization of direct ethanol fuel cells (DEFCs). Herein, we design a facile route to fabricate AuPd nanowires as highly efficient electrocatalysts toward ethanol oxidation reaction (EOR), where AuPd nanowires were in-situ assembled through the co-reduction of HAuCl4 and PdCl2 in aqueous solution in the presence of Triton X-114 and with potassium borohydride as the reducing reagent. The surface microstructure and composition of AuPd alloyed nanowires with the diameter of 4 nm were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and high resolution-transmission electron microscopy (HR-TEM). Among the AuPd NWs series, Au8Pd3 NWs demonstrated the best electrocatalytic activity (mass activity 10,570 mA mg−1Pd) and enhanced durability for ethanol electroxidation (retained 54% after 300 cycles) among the samples. The enhanced activities in EOR can be ascribed to the synergic electronic and structural effects of AuPd NWs. This work can provide a feasible method to boost Pd-alloy based electrocatalysts for EOR in direct ethanol fuel cells.

The development of advanced electrocatalysts for efficient catalyzing ethanol oxidation reaction (EOR) and oxygen reduction reaction (ORR) is significant for direct ethanol fuel cells (DEFCs). However, in many previous studies, the major difficulties including lower utilization efficiency and weaker anti-CO-poison ability of Pt hamper the practical testing of such DEFCs. Herein, ternary Pt22Pd27Cu51 ultrathin (~5 nm) NWs are fabricated via a facile surfactant-free strategy. The surface and electronic structures of Pt22Pd27Cu51 NWs are further tailored via acid-etching treatment. The resulted PtPdCu NWs with an optimal atomic Pt/Pd/Cu ratio of 36:41:23 display excellent specific activities towards EOR (4.38 mA/cm2) and ORR (1.16 mA/cm2), which are 19.8- and 5.7-folds larger than that of Pt/C, respectively. A single-cell was fabricated using Pt36Pd41Cu23 NWs as electrocatalyst in both anode and cathode with Pt loading of 1.2 mgPt/cm2. The power density measured at 80 °C is 21.7 mW/cm2, which is ~3.9 folds enhancement relative to that fabricated by using Pt/C (2 mgPt/cm2). The enhanced catalytic performance of Pt36Pd41Cu23 NWs could be attributed to that synergistic effect between Pt, Pd and Cu enhances CO anti-poisoning ability and promotes the C–C bond cleavage. This work provides a promising strategy for developing efficient electrocatalysts for DEFCs.

s For the first time, reduced graphene oxide (RGO) and nitrogen doped RGO (N-RGO) are prepared by the electrochemical procedure and then decorates with palladium nanoparticles via a solvothermal method to obtain Pd/RGO and Pd/NRGO. The as-synthesized electrocatalysts are characterized by transition electron microscopy (TEM), x-ray photoelectron (XPS), energy dispersive spectroscopy (EDS) and Fourier-transform infrared spectroscopy (FTIR) techniques. The bare RGO and NRGO electrodes are very active for the oxygen reduction reaction (ORR) and ethanol tolerance, providing the best performance in terms of tafel slope and onset potential. But, the resulting Pd/NRGO electrocatalyst shows outstanding electrocatalytic performance toward both ORR and ethanol oxidation reaction (EOR), including higher peak current density and low tafel slope than that of Pd/RGO, which can be related to high electrochemical active surface area of Pd/NRGO (53 m2 g−1) than that of Pd/RGO (41 m2 g−1). Finally, the fabricated anionic alkaline Membrane-electrode assemblies (MEAs) by using RGO, NRGO, Pd/RGO and Pd/NRGO are studied in single air-breathing direct ethanol fuel cell, as anode and cathode, with solutions of 4 M ethanol and 2 M KOH at room temperature.

Direct Ethanol Fuel Cells (DEFCs) structures compose membrane that separate anode and cathode. Membrane is vital structure, that play an essential role in facilitating electrochemical reaction. The crucial characteristics of an excellent membrane to be applied in DEFCs should posses high ionic conductivity. However, current membrane in DEFCS relatively has lower ionic conductivity with a high price. Membrane conductivity is obtained from the measurement of resistivity of the proton-conductive membrane against the flow of current. Ionic conductivity measured by electrochemical impedance spectroscopy (EIS) using electrochemical system. In this study, the Anion Exchange Membrane (AEM) using Methyllcellulose as host was fabricated using simple casting solution technique with KOH as doping salt and Polyetylene glycol as plasticizer. The effects of weight variations of KOH and Polyethylene glycol (PEG) were investigated on conductivity measurements of membrane. The optimal ratio of AEM using MC, KOH and PEG was performed via Central Composite Design (CCD) experiment. Based on the hierarchical agglomerative cluster analysis (HACA) approach, the results are grouped into their own clusters which shows the most reliable results. The optimum weight of plasticizers recorded is 1.5 g, 0.55 g, and 1.0 g for MC, KOH and PEG respectively yield the maximum conductivity which is 0.00025305 S/m. In summary, the findings of proper ratio weight of each compound are crucial to enhance the conductivity value.

Made available in DSpace on 2020-12-12T02:42:51Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-10-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) In this work electrocatalysts based on Pd and Sn nanoparticles supported on Vulcan XC-72 carbon black with a reduced amount of Pd were prepared. We evaluated its electrocatalytic activity for ethanol oxidation reaction (EOR) in alkaline direct ethanol fuel cells (ADEFCs). The electrocatalysts were synthesized in different Pd:Sn mass ratios (1:3, 1:1, 3:1 and 1:0) on the carbon containing 20 wt % of metal. The XRD patterns of the electrocatalysts revealed an alloy formation between Pd and Sn, and the electrocatalysts with lowest amount of Pd (Pd1Sn3/Vulcan XC-72) and highest electrochemically active surface area (ECSA) presented best performance in ADEFC experiments with a maximum current density and power density of 152 mA cm-2 and 42 mW cm-2, respectively. Besides the current density three times higher for EOR than that of the pure Pd, the open circuit potential of 939 mV at an operation temperature of 80 °C yielded the higher carbonate production. This behavior can be attributed to the presence of oxophilic Sn species, which improve the ability to remove adsorbed CO. Oxygenated species, vacancies and defects detected in the structure of PdxSny/Vulcan XC-72 catalysts are accounted for their high activity, making them very promising for the application in ADEFC. Laboratório de Eletroquímica e Materiais Nanoestruturados (LEMN) - Centro de Ciências Naturais e Humanas (CCNH) Universidade Federal do ABC (UFABC), Rua Santa Adélia 166, Bairro Bangu Instituto Federal de Educação Ciência e Tecnologia do Maranhão (IFMA) Campus Açailândia, R. Projetada, s/n Instituto de Química UNESP Universidade Estadual Paulista Instituto de Química UNESP Universidade Estadual Paulista FAPESP: 2015/10314-8 FAPESP: 2017/00819-8 FAPESP: 2017/10118-0 FAPESP: 2017/21846-6 FAPESP: 2017/22976-0 FAPESP: 2017/26288-1 FAPESP: 2018/26307-9 CNPq: 406612/2013-7

Electrocatalyst support materials play significant role in the performance, durability and commercialization of fuel cells. This research work describes the preparation of metal oxide (nickel oxide (NiO), cobalt (Co) and copper (Cu) doped NiO) support materials on meshed titanium (Ti) substrate via a simple electro-deposition method for their application as novel support material for palladium (Pd) catalyst. Field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) techniques are employed to study morphology, composition and structure of fabricated electrodes, respectively. The electrocatalytic performance of fabricated electrodes toward ethanol oxidation reaction (EOR) in alkaline solution is examined by the cyclic voltammetry (CV), chronoamperometry (CA) techniques. Low peak potential (−0.2 V), increased peak current density (62.54 mA cm−2) and large electrochemical active surface area (16.02 m2 g−1) were remarkable properties of Pd/Cu–NiO/Ti electrode. The results of other electrochemical measurements, CO-striping voltammetry, long-term stability and electrochemical impedance spectroscopy (EIS) revealed that the Pd/Cu–NiO/Ti electrode has the privileged electrocatalytic performance for EOR relative to other prepared electrodes. Accordingly, the Pd/Cu–NiO/Ti can be considered as a hopeful electrode for ethanol electro-oxidation reaction in DEFCs.

The conventional anode design of direct ethanol fuel cells (DEFCs) usually encounter a problem on the performance stability and ethanol mass transport, i.e., ethanol crossover. Aiming to alleviate these issues, in this study, the anode with different configurations for DEFC was designed and fabricated with different catalyst layer (CL) and microporous layer (MPL) arrangements. The four types of membrane electrode assembly (MEA) is named with MEA-1 (with pretreated carbon paper (PCP) and PtCL), MEA-2 (with PCP, MPL and PtCL), MEA-3 (with PCP, MPL, PtCL and PdCL) and MEA-4 (with PCP, MPL, PtCL, MPL and PdCL). The performance, stability and ethanol crossover of MEAs were tested and measured for continuous long-term operation for 120 h, while the morphological characterization was analyzed. Based on the results, power density for each MEA decreased with time, while ethanol crossover increased gradually. The MEA-3 with additional PdCL shows a highest performance and stability about 20 W/m2, and has a lowest ethanol crossover's magnitude. The highest ethanol crossover was obtained using MEA-1 at 3.7 mg/m2·s. Higher ethanol crossover had caused low stability of DEFC performance which result higher irreversible degradation. Moreover, based on characterization, elemental mapping and EDX illustrated phenomena of membrane swelling, delamination of electrode from membrane, and CL loss after stability test for 5 days for all MEAs. The significance of anode structure design was proven in this current study. The anode design of double-layered CL has potential to use at anode structure to reduce ethanol crossover rate, thereby improving DEFC performance and stability.

Nickel foam has been applying as the electrode support material for alkaline direct ethanol fuel cells, since its unique three-dimensional network structure helps efficiently use the catalyst to improve the cell performance. In this work, the effect of the thickness of nickel foam electrodes on cell performance is investigated. The experimental results show that the nickel foam thickness influences both the electron conduction and mass transfer, and the optimal thickness is a trade-off between them. Through XRD, SEM image, polarization curve test, EIS test and CV test, it is found that the nickel foam electrode with the thickness of 0.6 mm has better performance than that of 0.3 mm and 1.0 mm. The thinner the nickel foam, the better the conductivity. However, the corresponding three-dimensional space becomes narrower, which leads to partial agglomeration of the catalyst and hindrance of mass transfer. In addition, the influence of catalyst loading on the performance of 0.6 mm nickel foam electrode is explored. The maximum power density of 1.0 mg cm−2 Pd loading reaches 56.3 mW cm−2 at 60 °C, which is higher than that of 2.0 mg cm−2 loading, indicating that the three-dimensional network structure of nickel foam can efficiently utilize the catalyst, and fully exert the catalytic function of the catalyst even at a lower catalyst loading. Moreover, the effects of operating temperature and ethanol concentration on cell performance are also studied. The cell performance increases with the increase of temperature, and it reaches the highest with 3 M ethanol.

Pt-Ru and Pt–Re and Pt-Ru-Re nanoparticles supported on functionalized multi-walled carbon nanotubes (f-MWCNT) were synthesized via modified polyol reduction method and tested thoroughly in a half cell and single direct ethanol fuel cell for ethanol electrooxidation in acidic medium. The MWCNTs were functionalized in a mixture of HNO3/H2SO4 solution for depositing a more active metal alloy nanoparticle on support material. The alloy formation of bi-metallic and tri-metallic electrocatalysts were examined by XRD analysis and more clearly explained by FE-SEM element mapping. The TEM analyses reveal that electrocatalysts nanoparticles are well dispersed on f-MWCNT, with spherical shapes and nano sizes range of 1.5–4 nm. The electrochemical analyses by cyclic voltammetry and chronoamperometry measurements reveal that tri-metallic electrocatalyst Pt-Ru-Re (1:1:0.5)/f-MWCNT exhibits the highest electrocatalytic activity and stability towards ethanol electrooxidation among all the synthesized electrocatalysts. The same electrocatalyst as anode in single DEFC results in excellent performance in comparison to all other synthesized electrocatalysts, with a maximum power density of 9.52 mW/cm2 at a cell temperature of 30 °C. The bi-metallic Pt-Ru (1:1)/f-MWCNT and Pt–Re (1:1)/f-MWCNT produced power density of 7.48 mW/cm2 and 4.74 mW/cm2 at room temperature of 30 °C. The power density of DEFC enhanced 2.44 times, when cell operating temperature was increased from 30 °C to 80 °C using anode electrocatalyst Pt-Ru-Re (1:1:0.5)/f-MWCNT and keeping other parameters constant. The best result obtained in half cell and single DEFC using Pt-Ru-Re (1:1:0.5)/f-MWCNT electrocatalyst may be attributed to the synergistic effect of Pt, Ru and Re combined with bi-functional and ligand effects.

Pd1Nb1/C on different kinds of carbon black were prepared by a modified sol-gel method. The alkaline direct ethanol fuel cell (ADEFC) performance was performed first with the Pd1Nb1 electrocatalysts and then by varying the fuel concentration. In CV, Pd1Nb1/Printex 6L (50:50 wt%) exhibited 2.2 times higher mass activity than that of the Pd/C (Alfa Aesar); their mass activities were 1300 and 590 mA mg Pd − 1 , respectively. The best performance for the ADEFC was obtained using Pd1Nb1/Printex 6L, which yielded a maximum power density and cell voltage of 28 mW cm−2 and 1.17 V, respectively. The Pd1Nb1/Printex 6L electrocatalyst exhibited a more negative onset potential for the CO stripping reaction. We suggest that the higher hydrophilicity (contact angle) and higher degree of disorder of Printex 6L (Raman) corroborates these results. In addition, both bifunctional and electronic effects operated on the electrocatalyst due to the presence of metal oxides and alloys of PdNb (XRD), respectively, in the synthesized electrocatalysts. Therefore, it was notable that the support has an essential role—as important as the cocatalyst—in the electrocatalytic performance.

The electrocatalytic performance of Polypyrrole-Copper oxide particles modified carbon paste electrode (Cu2O/PPy/CPE) for electrocatalytic oxidation of ethanol was reported for the first time in alkaline media. The composite Cu2O/PPy was prepared using a facile approach consisting on the deposition of Polypyrrole film on CPE using galvanostatic mode then followed by the deposition of Copper particles at a constant potential. Scanning electron spectroscopy (SEM), infrared spectroscopy (FTIR), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were employed to characterize the structural and electrochemical properties of the Cu2O/PPy/CPE and to explain the mechanism of electrooxidation of ethanol. The experimental parameters that influence the electrooxidation of ethanol were investigated and optimized. Our findings suggest that the electrodeposition of Copper particles on Polypyrrole film enhanced the catalytic activity towards the ethanol oxidation with a peak current density of 2.25 mA cm−2 at 0.8 V vs Ag/AgCl, which is 2.6 times higher than the peak current density obtained by PPy/CPE electrode. It important to note that the saturation limit reaches a value of 5 M. To summarize, the good catalytic activity, stability and easy preparation make the Cu2O/PPy composite as an excellent electrocatalyst for ethanol oxidation.

A highly electroactive nickel nanorod (NNR)/nickel foam (NF) electrode was fabricated for direct alcohol fuel cells (DAFCs) using a simple and cost-effective hydrothermal process. The Ni/NiO nanorods were successfully grown on the surface of an NF electrode, which strongly enhanced the anode wettability and increased surface area by 18 times (11.9 m2 g−1), resulting in interfacial polarization resistance reduction. The NNR/NF electrode shows high electro-catalytic activity and great stability during alcohol oxidation. The current densities obtained for NNR/NF were four (479 mA cm−2) and six (543 mA cm−2) times higher than that for pristine NF in the cases of methanol and ethanol oxidations, respectively. This high current density can be attributed to the superhydrophilic surface of the Ni/NiO nanorods and corresponding high mass transfer capability between the electrolytes and Ni/NiO nanorods embedded on the surface of the electrodes. This study presents a new approach for using the novel NNR/NF as a cheap and high performance anode in DAFCs.

Highly dispersed Pt-Ru nano electrocatalysts supported on functionalized acetylene black carbon (CAB) were synthesized by a modified polyol reduction route followed by post treatment under three different conditions. The synthesized Pt-Ru/CAB-syn electrocatalysts after post treatment were designated as Pt-Ru/CAB-H2-RT when treated under H2 atmosphere at room temperature of 40 °C, and Pt-Ru/CAB-H2-160 when treated under H2 atmosphere at 160 °C and Pt-Ru/CAB-Air-160 when treated under air at 160 °C, respectively. The post treatment of synthesized electrocatalyst modified the crystallographic and morphological structures of the synthesized electrocatalysts which enhanced the electrocatalytic activity for ethanol electrooxidation. The physical characteristics of the post-treated electrocatalysts were recorded using XRD, SEM-EDX and TEM techniques. The XRD and TEM analyses revealed that the synthesized electrocatalysts have particle size in nano range with narrow size distribution. The electrochemical study of synthesized electrocatalysts were evaluated via cyclic voltammetry and chronoamperometry revealed that the Pt-Ru/CAB-H2-RT electrocatalyst is the most active exhibit towards ethanol electrooxidation in comparison to that of Pt-Ru/CAB-H2-160, Pt-Ru/CAB-Air-160 and commercial Pt-Ru/C electrocatalysts. In DEFC performance test at a temperature of 40 °C, the obtained power density (9.15 mW/cm2) using the synthesized Pt-Ru/CAB-H2-RT as anode electrocatalyst was higher than that of Pt-Ru/CAB-Air-160 (5.79 mW/cm2), Pt-Ru/CAB-H2-160 (6.84 mW/cm2) and commercial Pt-Ru/C (7.86 mW/cm2) electrocatalysts with same anode electrocatalyst loading of 1 mg/cm2 and 2 M ethanol fuel. The maximum OCV of 0.737 V and power density of 16.23 mW/cm2 at 0.317 V with a current density of 51.2 mA/cm2 were obtained using Pt-Ru/CAB-H2-RT electrocatalyst as anode at a cell temperature of 80 °C. The enhanced and superior performance of Pt-Ru/CAB-H2-RT electrocatalyst after post treatment could be attributed to well alloyed microstructure and highly dispersed surface morphology of metal nanoparticles.

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.

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.

[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.

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.

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.

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%.

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.

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.

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.

Pt bimetallic nanoparticles supported on N-doped reduced graphene oxide (NrGO) can increase catalytic activities in Anode for Hydrogen Fuel Cell, also in Direct Ethanol Fuel Cell (DEFC) when compare with Pt nanoparticles. In this study, PtNi and PtRu nanoparticles supported on NrGO can be prepared by microwave-assisted method while PtSn nanoparticles supported on NrGO can be prepared by NaBH4 reduction method. NrGO can be prepared by Modified Hummers Method, then reduced by annealing under Nitrogen gas atmosphere and N-added by annealing with melamine. The X-Ray Diffraction (XRD) patterns display the alloy forms of Pt-M alloy nanoparticles (M = Ni, Sn, Ru), which can be confirmed by Energy dispersive spectroscopy (EDS) data and electron diffraction (SAD) patterns. Particle sizes were measured from TEM images. Hence, this paper presents the average particle sizes of PtNi = 14.58±14.33 nm, PtRu = 6.01±1.44 nm and PtSn = 5.24±0.81 nm. Catalytic activity of these materials will be tested by fuel cell test station to confirm the superior activity over commercial Pt/C catalyst.

There are two significant characterizations of anion exchange membrane (AEM membrane) that affect the performance of passive direct ethanol fuel cells (DEFCs), namely ionic conductivity and ethanol permeability. Reducing the AEM membrane thickness leads to an increase in ionic conductivity by decreasing ion diffusion distance. Unfortunately, decreasing the AEM membrane thickness causes high ethanol permeability occurred, which deteriorates the performance of passive DEFCs. Therefore, it is necessary to balance two significant characterizations and obtain the optimal AEM membrane thickness to achieve high membrane selectivity and enhanced the performance of passive DEFCs. In this study, the effect of membrane thickness of Quaternized sodium alginate/polyvinyl alcohol (QSA/PVA) membrane was investigated to enhance the performance of passive DEFCs. The various membrane thicknesses from 12 μm to 24 μm were investigated. Based on our previous research, QSA/PVA membrane demonstrated dense morphology and virtuous characterization for AEM membrane, which is potentially for use in passive DEFCs. The 20 μm thickness membrane of the QSA/PVA membrane obtained the highest membrane selectivity (i.e., 13.57 × 104 S s cm-3), and the maximum power density of passive DEFCs reached 11.2 mW cm-2. Finally, the QSA/PVA membrane has successfully maintained the operating condition without cell degradation for 1000 hours.

The current study reports the preparation and investigation of several Pt-based anode catalysts loaded on reduced graphene oxide (rGO) as electrocatalysts in both acid and alkaline media for ethanol electrooxidation. The synthesized catalysts are evaluated by the method of XRD, Raman spectroscopy, XPS and TEM. Electrocatalytic properties of these catalysts for ethanol oxidation were investigated by cyclic voltammetry and chronoamperometry. It was found that the as-prepared nanocatalysts doped by metals and oxide metals showed the improvement of catalytic performance compared to Pt-only supported on graphene catalyst. The results indicated that the presence of Al favoured Pt nanoparticles dispersing on the surface of rGO sheets. Indeed, the PAG catalyst exhibits the highest mass activity for the ethanol oxidation of 1194 mA mg−1Pt in acid medium and 3691 mA mg−1Pt in alkaline medium. In addition, the PAG catalyst also shows good antipoisoning ability for ethanol electrooxidation in both media. This catalyst could be a potential catalyst for direct ethanol fuel cell (DEFC).

Direct ethanol fuel cells (DEFCs) have the potential to play a valuable role in the conversion of energy from sustainable sources. DEFCs need a support matrix, typically carbon, for the noble metal catalyst. In this work, two distinct carbon supports are compared and their electrochemical efficacy is related to their physicochemical characteristics. Specifically, Vulcan (Cv) is compared to Selectivity (Cs) as a support for Pd nanoparticles to catalyze ethanol electrooxidation. Characterisation data show that Cs has potentially favorable properties such as a high surface area. However, Pd/Cv exhibits a superior catalytic performance due to the higher adequacy of Cv texture that meets the particular needs of DEFC support in terms of pore size distribution. Additionally, synthesis of Pd nanoparticles on both carbons has decreased their surface areas and increased their pore sizes.

Metal complexes of N4-macrocycles such as porphyrins and phthalocyanines have been studied for several decades as alternatives to Pt catalysts in polymer electrolyte fuel cells (PEFCs) and polymer electrolyte membrane (PEM) water electrolyzers. This review mainly describes the recent development of these catalysts for use in anode and cathode of PEFCs and PEM water electrolyzers. Performance of the developed catalysts and strategies of the development are summarized. This review aimed to discuss the advantages and disadvantages of the metallomacrocycle-based catalysts compared to conventional Pt electrocatalysts, and to emphasize their functions that the Pt catalyst does not have.

In this paper, we use a three-dimensional mathematical model to analyze the flow in a direct ethanol fuel cell (DEFC). The overpotential losses are estimated based on the operating parameters of the cell, and based on the reactive flow within the channels, in the diffusion layer, and on the electrocatalyst surface. The model includes fuel consumption and the formation of acetic acid and acetaldehyde, and the rate of ethanol crossover through the membrane. The numerical simulation of the reactive flow was made based on the central finite difference method. The equations were discretized in time using the Crank–Nicolson method. The model calculates the flow velocity and species concentration along the inlet channel, the diffusion layer and the catalyst surface. The molar fraction of the species is calculated according to the current density in the DEFC. The results for the cell voltage versus current density were obtained for different catalysts on the anode side, for three temperatures and two initial concentrations of ethanol. The results obtained are consistent with the experimental data found in the literature.

The fuel cell is an electrochemical device that converts chemical energy directly into electricity and is more efficient than traditional power generators. In this work, we developed a mathematical model for a direct ethanol fuel cell (DEFC), which considers the flow and concentration of species dependent on time and space for the calculation of losses overpotentials. In addition, the concentration of each species is modeled according to the current density of the DEFC. The finite element method is used to calculate the flow and concentration of the species in different layers of the cell (inlet and outlet channels, diffusion layer and catalyst layer). The model takes into account the losses overpotentials at the anode and at the cathode and the passage of ethanol through the membrane. The voltage and power density of the cell are calculated with different catalysts, temperatures and concentrations of ethanol. A result is shown for limiting current density for low ethanol concentrations. The results obtained compare favourably with the data found in the literature.

The present investigation deals with the comparative analysis of electro-catalytic behaviour of Pt, Pd and ternary combinations of Co and Ni with Pd NPs, supported on vulcan XC72 as the anode component in direct ethanol fuel cell (DEFC) operating in alkaline environment. Catalyst NPs were synthesized by ethylene glycol reduction method and their structure, composition and surface morphology were determined through XRD, EDAX and TEM techniques. The superb catalytic efficiency of PdCoNi/C toward ethanol oxidation reaction (EOR) is ascribed to the catalytic intervention of transition metal ad atoms and their surface oxides, culminating to enhanced electrochemical surface area, preferred OH− adsorption on the surface and remarkable yield of oxidation products (CH3CO2− and CO32 −) estimated by ion chromatography. The performance output parameters collectively substantiate not only to the catalytic superiority of the PdCoNi/C catalyst but also affordability to a considerable extent over both the Pt/C and Pd/C catalysts.

Porous noble metal nanostructures with highly porous and extended surface areas are a long-desired target in both industry and academia. Among them, noble metal aerogels have emerged as state-of-the-art catalysts and these exceptional structures play crucial roles in various applications such as catalysis, sensors, etc. Until now, various methods have been published for the creation of noble metal aerogels, while their development and synthesis suffer from time-consuming multistep procedures. In this paper, we present an efficient method for the creation of porous three-dimensional network of Pd aerogel by a self-assembly process. This method offers several advantages over other methods such as being one-pot synthesis, simplicity and fast. Pd aerogel is synthesized by reducing H2PdCl4 in the presence of sodium carbonate using glyoxylic acid monohydrate as a reductant agent in a short time followed by supercritical drying. The Pd aerogel serves as an anode catalyst for the electrooxidation reaction of ethanol and exhibits superior electrocatalytic activity and durability compared to Pd/C catalyst. We believe that the Pd aerogel synthesized via this method is a promising catalyst for direct ethanol fuel cells (DEFCs) and will also open large opportunities for other applications.

Highly dispersed Ptshell-Pdcore catalyst is synthesized via an electroless deposition and a galvanic displacement. From electrochemical analysis, the catalyst is confirmed to be active toward an ethanol oxidation reaction for a prolonged time, and is more resistive against COad-poisoning than a conventional Pt/C catalyst. The stable activity of Ptshell-Pdcore/C is ascribed to the modified electronic property of Pt over-layer, which leads to a weak CO-adsorption strength with a high affinity for OH. The weakened binding property of surface Pt with COad was experimentally confirmed by conducting a COad-stripping and by measuring an electrochemically active surface area of the catalyst over multiple cycles. The COad oxidation ability of as-synthesized catalyst is further proved by a computational method via density functional theory (DFT) calculation. The result presents a potential application of the catalyst for the efficient ethanol oxidation in a direct ethanol fuel cell.

Made available in DSpace on 2018-12-11T16:50:23Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-05-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) National Natural Science Foundation of China Ethanol oxidation reaction (EOR) on Pd2Ru/C and Pd/C catalysts in alkaline media is studied comprehensively by cyclic voltammetry, chronoamperometry, in situ FTIR, single fuel cell test and electrochemical impedance spectroscopy measurements. The results show that, as compared to Pd/C, Pd2Ru/C favors acetaldehyde formation and hinders its oxidation. Based on X-ray absorption data, which evidence that Ru promotes a larger electronic vacancy of the Pd 4d band, it is expected that the formation of adsorbed ethoxy is favored on Pd2Ru/C and followed by its oxidation to acetaldehyde facilitated by oxygenated species provided by Ru. In contrast, acetaldehyde oxidation is more difficult on Pd2Ru/C than on Pd/C likely because the adsorption energy of the reactive species is increased. We also show that the performance of Pd2Ru/C anode in alkaline direct ethanol fuel cell (ADEFC) is initially better but degrades much more rapidly than that with Pd/C anode under the same test conditions. The degradation is demonstrated to result from the accumulation of large amounts of acetaldehyde, which in alkaline media forms dimers by the aldol condensation reaction. The dimers tend to be responsible for blocking the active sites for further ethanol oxidation. This comprehensive study provides new understandings of the roles of Ru in Pd2Ru/C for EOR in alkaline media, unveils the causes of the performance degradation of fuel cells with Pd2Ru/C and demonstrates that initial good performances are not necessarily a valid criterion for selecting appropriate anode catalysts for ADEFC applications. Richard G. Lugar Center for Renewable Energy Indiana University Purdue University Department of Chemical Engineering University of Toledo State Key Laboratory of Physical Chemistry of Solid Surfaces Department of Chemistry College of Chemistry and Chemical Engineering School of Energy Research Xiamen University Universidade Estadual Paulista (UNESP) Instituto de Química Universidade Estadual Paulista (UNESP) Instituto de Química FAPESP: 2013/50206-4 FAPESP: 2014/12255-6 National Natural Science Foundation of China: 21361140374

Palladium nanoparticles decorated reduced graphene oxide (Pd-rGO) and palladium nanoparticles intercalated inside nitrogen doped reduced graphene oxide (Pd-NrGO) hybrids have been synthesized by applying a very simple, fast and economic route using microwave-assisted in-situ reduction and exfoliation method. The Pd-NrGO hybrids materials show good activity as catalyst for ethanol electro oxidation for direct ethanol fuel cells (DEFCs) as compared to Pd-rGO hybrids. The enhanced direct ethanol fuel cell can serve as alternative to fossil fuels because it is renewable and environmentally-friendly with a high energy conversion efficiency and low pollutant emission. As proof of concept, the electrocatalytic activity of Pd-NrGO hybrid material was accessed by cyclic voltammetry in presence of ethanol to evaluate its applicability in direct-ethanol fuel cells (DEFCs). The Pd-NrGO catalyst presented higher electro active surface area (∼6.3 m2 g−1) for ethanol electro-oxidation when compared to Pd-rGO hybrids (∼3.7 m2 g−1). Despite the smaller catalytic activity of Pd-NrGO, which was attributed to the lower exfoliation rate of this material in relation to the Pd-rGO, Pd-NrGO showed to be very promising and its catalytic activity can be further improved by tuning the synthesis parameters to increase the exfoliation rate.

In recent years bi-metallic materials have shown promising effect as potential catalyst layer in the fuel cells. Here, for the first time, bimetallic Ag-Pd were electrodeposited on polyaniline/glassy carbon electrode (PANI/GCE) via the constant current method, which used as efficient electrode for ethanol oxidation reaction (EOR) in alkaline media. Some important parameters including applied current, deposition time and metal ratio were optimized. The obtained bimetallic AgPd/PANI/GCE catalyst showed improved catalytic performance for ethanol conversion compared with the Pd/PANI/GCE, Pd/GCE, Ag/PANI/GCE, and PANI/GCE. The catalytic enhancement is due to the synergic effect between Ag, Pd and PANI. Moreover, the proposed AgPd composite was deposited on the carbon fiber cloth (CC) to evaluate its applicability as an anode in ethanol fuel cell. To summarize, the good electrochemical performance and easy preparation make the obtained Ag-Pd bimetallic composite as a potential candidate for alkaline ethanol fuel cell.