Journal of the Electrochemical Society

/Journal of the Electrochemical Society

Journal of the Electrochemical Society

Synthesis, First-Principle Simulation, and Application of Three-Dimensional Ceria Nanoparticles/Graphene Nanocomposite for Non-Enzymatic Hydrogen Peroxide Detection

2019-01-25T16:31:15+00:00January 25th, 2019|Categories: Publications|Tags: |

Owing to the exceptional properties of graphene and the crucial role of substrate on the performance of electrochemical biosensors, several graphene-based hybrid structures have recently emerged, yielding improved selectivity and sensitivity. To date, most of the reported biosensors utilize solution-driven graphene flakes with drawbacks of low conductivity (due to high inter-junction contact resistant) and structural fragility. Herein, we present a conductive three-dimensional CeO2 semiconductor nanoparticles/graphene nanocomposite, as a platform for sensitive detection of hydrogen peroxide, an important molecule in fundamental biological processes. The 3D conductive graphene architecture is fabricated by chemical vapor deposition on nickel foam. The fabricated biosensor displays high sensitivity (60 μA.mM–1) at a low negative potential of –0.25 V, a low detection limit (<1.0 μM at S/N = 3), and a fast response (<5 s) in the range of 2.8 to 160 μM. Furthermore, density functional theory simulations show that the improved detection is not only related to the catalytic effect of ceria nanoparticles, but also to more efficient charge transfer from nanoparticles to the 3D graphene network. Moreover, it is established that the amperometric response of the biosensor is insensitive to interfering molecules such as glucose, sucrose, and potassium chloride, indicating its potential for practical applications.

Published in: "Journal of the Electrochemical Society".

Two Dimensional WS2/C Nanosheets as a Polysulfides Immobilizer for High Performance Lithium-Sulfur Batteries

2019-01-19T22:31:17+00:00January 19th, 2019|Categories: Publications|Tags: |

A dual function cathode consisting of tungsten disulfide and porous carbon nanosheets (WS2/C) was synthesized to improve the performance of lithium sulfur batteries. The well-defined structure is composed of ≤5 layers with 0.62 nm interlayer spacing corresponding to the (002) facial plane of WS2. The composite depicted very strong affinity toward lithium polysulfides. Rapid transport of lithium ions was also revealed. The cathode demonstrated excellent cycling stability and rate capability by delivering a reversible specific capacity of 419mAh g–1 at 8C after 500 cycles with low capacity fading at 0.04% per cycle. At high sulfur loading of 4.7mg cm–2 the batteries delivered 3.4mAh cm–2 areal capacity after 100 cycles at 0.5C. The synergistic effect of strong chemical interaction between lithium polysulfides and WS2, and the superior electronic conductivity of carbon nanosheets are responsible for the enhanced performance. It also suppressed the self-discharge phenomenon by maintaining 94.5% of its initial capacity after 10 days resting. The electrochemical impedance spectroscopy (EIS) analysis demonstrated that even after 400 cycles, the interfacial and charge transfer resistances only increased by 1.2 and 1.7, respectively, describing faster electrochemical kinetics by inhibiting the formation of insulating layer of lithium sulfide (Li2S) on the surface of the electrodes.

Published in: "Journal of the Electrochemical Society".

Incorporation of an Au-rGO Layer to Enhance the Photocatalytic Application of Optimized CdS Thin Film

2019-01-15T16:31:25+00:00January 15th, 2019|Categories: Publications|Tags: , |

Nanoscale architecturing of photoanodes with the improved photoelectrochemical activities for water splitting has been demonstrated by introduction of gold (Au) and reduced graphene oxide (rGO) to cadmium-sulfide (CdS). We optimized CdS thin film by an inert atmosphere heat-treatment, on which Au-rGO-coated CdS ([email protected]) could be obtained by sequential deposition of rGO and Au. The morphology, structure and optical and vibrational properties of the CdS and [email protected] samples were found to be in good correlation with the photoelectrochemical analysis. The [email protected] thin film showed a current density of 5 mA/cm2 at 0 V (vs SCE), which is approximately 3.5 times higher than that of the as-prepared CdS thin film. The enhancement mechanism has been discussed elaborately through the extensive photoelectrochemical characterization.

Published in: "Journal of the Electrochemical Society".

Electrochemical Properties of Titanium Oxides with Disordered Layer Stacking through Flocculation of Exfoliated Titania Nanosheets

2019-01-04T16:31:26+00:00January 4th, 2019|Categories: Publications|

A new type of layered titanium oxides with turbostratic stacking has been synthesized via flocculation of exfoliated titania nanosheets with HCl or LiOH. Nitrogen adsorption–desorption isotherms showed that the spray-dried flocculations had mesoporous structures composed of slit-shaped pores. Cross-sectional SEM and TEM analyses clarified that particles were composed of agglomerated highly twisted flakes. UV-Visible diffuse reflectance spectra of restacked titania nanosheets were depended on the restacking process and were significantly blue shifted compared with that for the parent layered compound. The product flocculated with HCl showed a high initial capacity of about 300 mAh g–1 (cutoff voltage: 1.0 V), whereas rechargeable capacities were gradually decreased during charge-discharge repetition. On the other hand, the heat-treated product restacked by LiOH showed a relatively good cyclability over the 50 cycles, indicating a rechargeable capacity of about 150 mAh g–1. X-ray absorption spectra and cyclic voltammograms gave the evidence of the redox reaction of titanium, and the average voltage depended on the type of layer stacking. The XRD analyses of electrodes after charge-discharge revealed that the cyclability depended on the stability of layer structure.

Published in: "Journal of the Electrochemical Society".

[email protected]@Ni Cathode Materials for Lithium-Selenium Battery

2018-12-29T18:31:36+00:00December 29th, 2018|Categories: Publications|Tags: , , |

Selenium is a promising cathode material for high-energy lithium batteries. In this work, selenium was electrodeposited on nickel foam from aqueous selenite solution. The influences of pH values and current density on electrodeposited [email protected] were investigated. It is found that electrodeposition at pH 7 and 0.5 mA cm–2 enables high current efficiency and produces uniform and smooth deposits. Graphene oxide (GO) was further coated on [email protected] through physical adsorption to produce [email protected]@Ni. The developed [email protected]@Ni electrode delivers a high initial specific capacity of 593 mAh g–1 and good capacity retention over 100 cycles at 0.1 C.

Published in: "Journal of the Electrochemical Society".

CuS/Graphene Nanocomposite as a Transparent Conducting Oxide and Pt-Free Counter Electrode for Dye-Sensitized Solar Cells

2018-12-29T18:31:32+00:00December 29th, 2018|Categories: Publications|Tags: |

We report a simple, low temperature and solution-processable approach to prepare a composite film of copper sulfide/graphene (CuS-G) as a transparent conducting oxide (TCO) and platinum (Pt)-free CE for Dye-Sensitized Solar Cells (DSSCs). We find that CuS with 3.3 vol% of graphene (CuS-3G) yields the highest power conversion efficiency (PCE) of 4.83%, which is about 12% higher than DSSCs based on CEs made of pristine CuS. After optimizing the graphene concentration, the PCE of the DSSC assembled with the optimized CuS-3G is comparable to that based on Pt CE. The similar performance of the CuS-3G CE compared with Pt CE is mainly attributed to the small series resistance and high electrocatalytic activity of the CuS-3G CE; this is confirmed by cyclic voltammetry and electrochemical impedance spectroscopy. These results indicate a straightforward methodology for the low cost and easy synthesis of an alternative CE in DSSCs.

Published in: "Journal of the Electrochemical Society".

Ordered Nanotubular Titanium Disulfide (TiS2) Structures: Synthesis and Use as Counter Electrodes in Dye Sensitized Solar Cells (DSSCs)

2018-11-02T14:31:20+00:00November 2nd, 2018|Categories: Publications|Tags: |

TiS2 nanotubular structures were synthesized by a high temperature H2S treatment of anodized TiO2 nanotube layers, and their electrochemical activity for a use as counter electrodes in dye sensitized solar cells (DSSCs) was evaluated. During conversion to TiS2 compositional, morphological and structural transformations were monitored. The fully converted TiS2 nanostructures show a high electrocatalytic activity for the I–/I3– oxidation comparable to a nanoparticular platinum layer. For a simplified model a DSSC solar cell efficiency of 6.1% was obtained using the TiS2 nanotube layer as counter electrode, which is very close to values obtained for a Pt reference (6.2%).

Published in: "Journal of the Electrochemical Society".

Manganese Oxide/Hemin-Functionalized Graphene as a Platform for Peroxynitrite Sensing

2018-08-16T14:31:50+00:00August 16th, 2018|Categories: Publications|Tags: , , |

Peroxynitrite (ONOO–, PON) is a powerful oxidizing agent generated in vivo by the diffusion-limited reaction of nitric oxide (NO) and superoxide (O2{dot}–) radicals. Under oxidative stress, cumulated peroxynitrite levels are associated with chronic inflammatory disorders and other pathophysiological conditions. The accurate detection of peroxynitrite in biological systems is important, not only to understand the genesis and development of diseases, but also to explore and design potential therapeutics. Herein, a manganese oxide/hemin-modified graphene interface is explored as a platform for peroxynitrite amperometric detection. Hemin-functionalized reduced graphene oxide was further modified with manganese oxide nanoparticles to provide a composite material with catalytic activity toward the electrochemical oxidation of peroxynitrite. The morphology of the composite material was characterized using scanning electron microscopy, energy dispersive X-ray analysis, X-ray photoelectron spectroscopy, and UV-Vis absorption measurements. We investigated the electrocatalytic oxidation of peroxynitrite on graphite electrodes modified with the composite material using cyclic voltammetry and amperometry. The results showed that the incorporation of manganese oxide nanoparticles into graphene/hemin material enhances the catalytic detection of peroxynitrite compared to graphene/hemin alone.

Published in: "Journal of the Electrochemical Society".

Electrochemically Exfoliated Carbon Quantum Dots Modified Electrodes for Detection of Dopamine Neurotransmitter

2018-08-09T16:31:21+00:00August 9th, 2018|Categories: Publications|

A simple electroanalytical method was developed to detect dopamine (DA) neurotransmitter by using carbon quantum dots (CQDs) modified electrode. To synthesis CQDs, a green electrochemical method was adopted and graphite rods were used as anode and cathodes in 0.1 M NaOH/ethanol (EtOH) as the electrolyte solution. As-synthesized CQD showed different particle sizes depending on the applied current with time as characterized by UV-visible spectroscopy. The particle size, lattice structure and functional groups of CQDs were analyzed by the HR-TEM, XRD and FT-IR, respectively. The CQD exhibited a green fluorescence under UV light (365 nm). Moreover, CQD dispersion was used to modify glassy carbon electrode (GCE) and screen-printed carbon electrode (SPCE) to study their electrochemical and electrocatalytic properties. The both GCE/CQD and SPCE/CQD showed higher electrocatalytic activity toward oxidation of dopamine (DA) in phosphate buffered saline (PBS) solution (pH = 7.4). In order to avoid interferences, Nafion (Nf) layer was coated on the CQD film modified electrode. The effect of scan rate on DA oxidation was studied from 10 to 150 mV/s. The calibration curve was recorded for DA from 1 to 7 μM using a SPCE/CQD and the limit of detection was found to be 0.099 μM. The observed electro-catalytic activity of the CQD was attributed to their negatively charged functional groups which attracted positively charged DA in 0.1 M PBS. In addition, detection of DA in spiked human urine sample was demonstrated with satisfactory recovery analysis.

Published in: "Journal of the Electrochemical Society".

Nanoarchitectured CNTs-Grafted Graphene Foam with Hierarchical Pores as a Binder-Free Cathode for Lithium-Oxygen Batteries

2018-08-07T18:31:51+00:00August 7th, 2018|Categories: Publications|Tags: |

In this study, a three-dimensional CNTs-grafted graphene foam has been fabricated by a chemical vapor deposition method. The nanoarchitectured composite is employed as a cathode for lithium-oxygen (Li-O2) batteries and exhibits a substantially enhanced capacity of 20300 mAh g–1 at 0.05 mA cm–2, the number of which is among the highest prototype Li-O2 batteries reported to date. And the cathode can still exhibit a capacity of 3000 mAh g–1 when the current density is increased to 0.15 mA cm–2. The improved performance, e.g., discharge capacity and rate capability, is mainly attributed to the synergistic effects of CNTs and graphene, which not only provide an effective channel for the transportation of oxygen and Li ion but also offer more and fast pathways for electron transport. In addition, the forest distribution of CNTs hinders the restack of graphene, contributing to the stability of Li-O2 batteries. This study demonstrated that the CNTs-grafted graphene foams would be likely to be a good alternative cathode material for Li-O2 batteries in the future.

Published in: "Journal of the Electrochemical Society".

Low Temperature Sulfur Deposition for High-Performance Lithium/Sulfur Cells

2018-08-07T16:32:27+00:00August 7th, 2018|Categories: Publications|Tags: , |

Sulfur deposition is an effective method for creating composites of sulfur with various conductive materials. In this study we investigated the details of the deposition process of sulfur onto graphene oxide (GO). It was revealed that just mixing a polysulfide solution and a GO suspension resulted in the deposition of sulfur onto the GO under alkaline conditions. The combination of the alkaline deposition and subsequent acidic deposition at different temperatures yielded materials with various morphologies. The sulfur deposition rate influenced the morphology of the S deposit and the resulting Li/S cell performance. By controlling the process with a moderate time for the alkaline deposition and subsequent acidic deposition at a decreased temperature, a preferred morphology of the sulfur/GO composite with a high sulfur utilization was successfully synthesized. This preferred morphology of SGO provides for a high-performance Li/S cell.

Published in: "Journal of the Electrochemical Society".

Computer Study of Atomic Mechanisms of Intercalation/ Deintercalation of Li Ions in a Silicene Anode on an Ag (111) Substrate

2018-08-07T16:32:21+00:00August 7th, 2018|Categories: Publications|Tags: |

The ability of silicon to hold a large amount of lithium puts silicene in a series of the most promising materials for the anode of lithium-ion batteries. An increase in the rate of movement of lithium ions through silicene can be achieved with silicene having vacancy-type defects. The effect of vacancy-type defects on the fill ability with lithium of the channel formed by silicene sheets on the Ag (111) substrate, as well as on the structural and kinetic properties of lithium, has been studied by the molecular dynamics method. The limit number of intercalated lithium atoms and their self-diffusion coefficient increase with the transition from the perfect silicene channel to the channel containing mono- and bivacancies. The lithium structure in the channel was studied using the method of statistical geometry. The packing of the lithium atoms in the channel turns out to be partially ordered due to the regular placement of some of the atoms at their fixation opposite the centers of hexagonal Si-cells. The zz stress in the sheets of silicene decreases during intercalation of lithium and increases at the final stage of deintercalation.

Published in: "Journal of the Electrochemical Society".

Tannic Acid-Decorated Spongy Graphene for Flexible and High Performance Supercapacitors

2018-08-07T16:32:11+00:00August 7th, 2018|Categories: Publications|Tags: , , |

A simple method was developed to prepare tannic acid-decorated spongy graphene hydrogel (TAGH) as interconnected, three-dimensional (3D) porous network supercapacitor electrode materials. Tannic acid (TA) not only can be fully competent in reducing graphene oxide and stabilizing reduced graphene oxide, but also can prevent graphene sheets from agglomerating by suppressing the – stacking interactions. Such 3D porous TAGH electrodes with low charge transfer resistance of 0.4 .cm2 displayed a maximum specific capacitance of 533 F/g at 0.5 A/g. The assembled TAGH supercapacitor showed a good cycling stability (84.6% capacitance retention after 8000 charging/discharging cycles) and mechanical flexibility (93.4% capacitance retention after 500 folding/unfolding cycles). Remarkably, the flexible device can achieve superior energy density of 37.0 Wh/kg and higher power density of 4476.7 W/kg. These results demonstrate a great potential for application of 3D TAGH electrodes in flexible, high performance wearable electronics and energy storage devices.

Published in: "Journal of the Electrochemical Society".

Suspension Characteristics and Electrophoretic Deposition of p-Type Bi2Te3 Films for Thermoelectric Applications

2018-08-07T16:32:08+00:00August 7th, 2018|Categories: Publications|

Electrophoretic deposition (EPD) was utilized to prepare uniform crack-free Bi2Te3 films for thermoelectric applications effectively. A p-type Bi2Te3 film with a coherent structure and even thickness was deposited from Tetrahydrofuran (THF) suspensions and examined using a scanning electron microscope (SEM). The specific weights of the depositions, the effective percentile coverage of the films on the substrate, the zeta potential and the electrical conductivity of different suspensions and the in-plane Seebeck coefficients of the Bi2Te3 films were measured. Although the Seebeck coefficient value of the EPD film (126 μV/K) was approximately 25% lower than the highest value reported for Bi2Te3 in the open literature via the co-sputtering method (160 μV/K), one of the most complex and expensive routes, the cost-effectiveness and speed of the simple EPD process is an undeniable advantage. This could open up new opportunities in the application of films to commercialize thermoelectric generators (TEG). It is interesting to note that the value of the Seebeck coefficient for our EPD-fabricated film was higher than for some of the other types of coatings prepared via more expensive and sophisticated fabrication routes, such as the electrodeposition technique (80 μV/K), for example.

Published in: "Journal of the Electrochemical Society".

Co-Mn Hybrid Oxides Supported on N-Doped Graphene as Efficient Electrocatalysts for Reversible Oxygen Electrodes

2018-08-07T16:31:53+00:00August 7th, 2018|Categories: Publications|Tags: , |

Despite metal-air batteries possessing very high theoretical energy densities, inefficient reversibility of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) at the oxygen electrode undermines their rechargeability, which has slowed their market entry. Herein, we demonstrate a simple procedure for synthesis of a hybrid of MnO and metallic Co supported on N-doped graphene that exhibits activity and stability as a bifunctional ORR/OER catalyst, with a round trip ORR/OER overvoltage of 0.85 V, which remained constant for at least 70 h when cycling alternately, between oxygen evolution at a current density of 10 mA cm–2 and oxygen reduction at –1 mA cm–2. Insights into the key properties of the catalyst that influence its performance are proposed based on structural characterization by TEM, SEM, Raman spectroscopy, XRD and XPS. Besides MnO and metallic Co as the predominant crystalline species in the Co-Mn hybrid oxide, XPS revealed Mn3O4 and CoO rich surfaces, ascribed to oxidation of MnO and metallic Co due to atmospheric exposure. The synergetic interaction between the Co-Mn hybrid oxides and N-doped graphene, as well as Co-Mn interaction, favor improved ORR, OER and bifunctional ORR/OER performance of the catalyst.

Published in: "Journal of the Electrochemical Society".

Tunable Electrochemical Approach for Reduction of Graphene Oxide: Taguchi-Assisted Chemical and Structural Optimization

2018-08-07T16:31:49+00:00August 7th, 2018|Categories: Publications|Tags: , |

The effect of significant parameters on the tuning of electrochemical reduction of graphene oxide (GO) and its electrochemical behavior toward ferri/ferrocyanide as a redox couple was investigated for the first time through a systematic methodical procedure. Reduced graphene oxide (rGOs) modified electrodes were prepared by electrodeposition on the surface of indium tin oxide (ITO) electrode under various GO concentrations, solution pH, scan rate and number of cycles. Taguchi is experimental design method involving orthogonal arrays, signal to-noise (S/N) ratio, analysis of variance (ANOVA) were employed to optimize reaction parameters and to analyze their effects on GO reduction. Cyclic voltammetry (CV) and Fourier-transform infrared spectroscopy (FTIR) analysis revealed that redox activity was least dependent on pH and GO concentrations whereas the use of higher scan rate and lower number of cycles led to more reduction of GO. On the other hand, the electrochemical behavior of samples deposited at higher scan rates totally improved despite the assumption that applying more potential causes more reduction of oxygen functional groups of graphene which are recognized to enhance the electron transfer. Moreover, electrochemical impedance spectroscopy (EIS) showed a lower charge transfer resistance for rGO which was prepared at higher scan rate. Such contrasting finding is precisely discussed in the manuscript to unveil the logical reasons.

Published in: "Journal of the Electrochemical Society".

Highly Efficient Fe-N-C Nanoparticles Modified Porous Graphene Composites for Oxygen Reduction Reaction

2018-08-07T16:31:45+00:00August 7th, 2018|Categories: Publications|Tags: , |

Iron-nitrogen-carbon nanoparticles modified porous graphene (Fe-N-C/PGR) was synthesized from the pyrolysis of porous freeze-dried composites of iron (II) phthalocyanine (FePc) nanoclusters and graphene oxide (GO). By pyrolysis in argon atmosphere, the GO was reduced into graphene (GR), and the FePc nanoclusters were converted to Fe-N-C nanoparticles on the GR surface. The morphologies and composition of the resulted Fe-N-C/PGR composites were characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectra. The Fe-N-C/PGR composites exhibited three-dimensional interpenetrated porous structure, and many particles with Fe-N-C active sites were distributed on the GR nanosheets. Electrocatalytic properties of the Fe-N-C/PGR composites were investigated by cyclic voltammetry and linear sweep voltammetry. For the Fe-N-C/PGR composites with 3:1 mass ratio of FePc nanoclusters to GO precursor, it showed the highest electrocatalytic activity with the peak current density of 5.82 mA cm–2 at –0.39 V, which was ascribed to the synergistic effect of Fe-N-C active sites and PGR with good porous structures. The electron transfer number of 3.94 for the Fe-N-C/PGR composite indicated a direct 4-electron pathway for the ORR. Furthermore, the Fe-N-C/PGR composites showed high stability and better tolerance to methanol than the commercial 20% Pt/C catalysts.

Published in: "Journal of the Electrochemical Society".

Photocatalytic Activity of ZnV2O6/Reduced Graphene Oxide Nanocomposite: From Theory to Experiment

2018-08-07T16:31:37+00:00August 7th, 2018|Categories: Publications|Tags: , |

A nanocomposite of ZnV2O6 with hierarchical flower-like structure hybridized with reduced graphene oxide (rGO) was fabricated using a facile hydrothermal approach. The structure, morphology, optical and electronic properties were explored using comprehensive analytical techniques. The results revealed that the rGO sheets were decorated with the in situ-formed ZnV2O6 nanoparticles yielding a well-combined composite structure. The photocatalytic activity of as-prepared ZnV2O6/rGO hybrids is 2.48 times larger than that of pristine ZnV2O6 for the degradation of Rhodamine B (RhB). In parallel to the experimental results, the basic mechanisms of interfacial interaction, charge transfer/separation and subsequently their influence on the photocatalytic activity were theoretically studied by first-principles calculations. The photocatalytic enhancement is attributed to efficient interfacial electron transfer from ZnV2O6 to rGO, leading to a prolonged lifetime of photoinduced charge carriers. We anticipate that these results will lead to new insights in the judicious design of graphene-based semiconductor photocatalysts.

Published in: "Journal of the Electrochemical Society".

High-Performance Supercapacitors of N-Doped Graphene Aerogel and Its Nanocomposites with Manganese Oxide and Polyaniline

2018-08-07T16:31:36+00:00August 7th, 2018|Categories: Publications|Tags: , , |

Nitrogen-doped graphene aerogel (NGae) with a three-dimensional (3D) interconnected structure with ca. 3.5 at% of nitrogen content was synthesized by a hydrothermal reduction of graphene oxide with hydrazine and a following freezing-dry method. The 3D morphology of conductive NGae provides fast ion diffusion leading to nearly steady specific capacitances (ca. 450 F g–1) when increasing scan rates (10–100 mV–1) or applied currents (0.5–2.5 A g–1). Not only can the nitrogen-containing groups improve the electrical conductivity of NGae but also they can store charges via their reversible surface redox reactions. The as-fabricated symmetric supercapacitor of NGae in 1 M H2SO4 electrolyte provides a maximum specific energy and power of 42 Wh kg–1 and 2077 W kg–1, respectively. In addition, incorporating pseudocapacitor materials i.e., MnO2 and polyaniline to NGae structure can also provide higher specific energy owing to surface redox reactions. The as-fabricated supercapacitors in this work may be practically used in high energy and power applications.

Published in: "Journal of the Electrochemical Society".

Core-Shell [email protected] on Functionalized Graphene for Methanol Electrooxidation

2018-08-07T16:31:34+00:00August 7th, 2018|Categories: Publications|Tags: |

A simple but effective electrochemical route to functionalize graphene is demonstrated. Cyclic voltammetric sweeps (CV) are performed in a 0.5 M H2SO4 aqueous solution on electrodes consisting of carbon cloth, graphene, and Nafion ionomer. Upon exposure to ambient oxygen, the formation of hydroxyl radicals from the oxygen reduction reaction during the CV cycles initiates the decomposition of the Nafion ionomer, which produces oxygenated functional groups on the graphene surface. Using contact angle measurements and X-ray photoelectron spectroscopy, various amounts of Nafion ionomer are explored to determine the optimum conditions for graphene functionalization. Afterwards, Pd9Ru nanoparticles with an average size of 3–4 nm are synthesized and impregnated on functionalized graphene (FGN). To prepare core-shell electrocatalysts, Pd9Ru/FGN is subjected to Cu underpotential deposition followed by a galvanic displacement reaction to deposit a Pt monolayer on the Pd9Ru surface ([email protected]). The as-synthesized sample ([email protected]/FGN) exhibits enhanced performance in methanol electrooxidation, which includes a better activity and lower susceptibility to poisoning by intermediates. The electrochemically active surface area (ECSA) of [email protected]/FGN shows a value that is 1.5-fold larger than that of [email protected] on untreated graphene ([email protected]/GN). In the durability tests, [email protected]/FGN and [email protected]/GN demonstrate losses in the ECSA of 14.9% and 30.3%, respectively.

Published in: "Journal of the Electrochemical Society".

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