Oxygen Reduction In Alkaline Media Research Articles

Order of Activity of Nitrogen, Iron Oxide, and FeNx Complexes towards Oxygen Reduction in Alkaline Medium.

In alkaline medium, it seems that both metal-free and iron-containing carbon-based catalysts, such as nitrogen-doped nanocarbon materials, FeOx -doped carbon, and Fe/N/C catalysts, are active for the oxygen reduction reaction (ORR). However, the order of activity of these different active compositions has not been clearly determined. Herein, we synthesized nitrogen-doped carbon black (NCB), Fe3 O4 /CB, Fe3 O4 /NCB, and FeN4 /CB. Through the systematic study of the ORR catalytic activity of these four catalysts in alkaline solution, we confirmed the difference in the catalytic activity and catalytic mechanism for nitrogen, iron oxides, and Fe-N complexes, respectively. In metal-free NCB, nitrogen can improve the ORR catalytic activity with a four-electron pathway. Fe3 O4 /CB catalyst did not exhibit improved activity over that of NCB owing to the poor conductivity and spinel structure of Fe3 O4 . However, FeN4 coordination compounds as the active sites showed excellent ORR catalytic activity.

Oxygen reduction catalyzed by nanocomposites based on graphene quantum dots-supported copper nanoparticles

Nanocomposites based on graphene quantum dots (GQDs)-supported copper nanoparticles were prepared by thermal refluxing of copper salts in 1,2-propanediol at 140 °C in the presence of GQDs. Transmission electron microscopic measurements showed that the resulting Cu/GQD nanoparticles increased from 5 to 15 nm in average diameter with increasing metal loadings. Raman spectroscopic measurements showed that all nanocomposites exhibited well-defined D and G vibrational bands. X-ray photoelectron spectroscopic studies indicated the formation of Cu2O and CuO in the nanocomposite particles, along with various defect concentrations within the GQD graphitic skeletons. Electrochemical studies showed that the nanocomposites exhibited apparent electrocatalytic activity in oxygen reduction in alkaline media, and the sample with a Cu/C atomic ratio of 2.88% exhibited the best ORR activity among the series, within the context of onset potential, number of electron transfer and kinetic current density. The performance was further improved by deliberate hydrothermal treatments of the sample, and 160 °C was identified as the optimal temperature, which was ascribed to manipulation of the electronic interactions between copper nanoparticles and oxygen intermediates by the GQD structural defects.

N-doped graphene coupled with Co nanoparticles as an efficient electrocatalyst for oxygen reduction in alkaline media

Development of low-cost and highly efficient electrocatalysts for oxygen reduction reaction (ORR) is still a great challenge for the large-scale application of fuel cells and metal-air batteries. Herein, a noble metal-free ORR electrocatalyst in the form of N-doped graphene coupled with part of Co nanoparticles encased in N-doped graphitic shells (named as SUCo-0.03-800) is prepared by facile one-step pyrolysis of the mixture of sucrose, urea and cobalt nitrate. The novel structure is confirmed by High Resolution-TEM, XRD, XPS and Raman spectroscopy. SUCo-0.03-800 presents comparable ORR catalytic activity to commercial Pt/C catalyst with a dominating four-electron pathway under alkaline conditions, and both of its mass activity and volume activity also outperform Co-free N-doped graphene and other Co/N–C hybrids with higher Co content, which may probably be ascribed to the high specific surface area, novel structure and synergistic effect between encased Co nanoparticles and N-doped graphitic shell. Additionally, SUCo-0.03-800 also shows outstanding stability and improved selectivity towards ORR, making it a promising alternative to Pt with potential application in fuel cells and metal-air batteries.

Nano-Structured Bio-Inorganic Hybrid Material for High Performing Oxygen Reduction Catalyst.

In this study, we demonstrate a non-Pt nanostructured bioinorganic hybrid (BIH) catalyst for catalytic oxygen reduction in alkaline media. This catalyst was synthesized through biomaterial hemin, nanostructured Ag-Co alloy, and graphene nano platelets (GNP) by heat-treatment and ultrasonically processing. This hybrid catalyst has the advantages of the combined features of these bio and inorganic materials. A 10-fold improvement in catalytic activity (at 0.8 V vs RHE) is achieved in comparison of pure Ag nanoparticles (20-40 nm). The hybrid catalyst reaches 80% activity (at 0.8 V vs RHE) of the state-of-the-art catalyst (containing 40% Pt and 60% active carbon). Comparable catalytic stability for the hybrid catalyst with the Pt catalyst is observed by chronoamperometric experiment. The hybrid catalyst catalyzes 4-electron oxygen reduction to produce water with fast kinetic rate. The rate constant obtained from the hybrid catalyst (at 0.6 V vs RHE) is 4 times higher than that of pure Ag/GNP catalyst. A catalytic model is proposed to explain the oxygen reduction reaction at the BIH catalyst.

Different Carbide Derived Nanoporous Carbon Supports and Electroreduction of Oxygen

Using rotating disc electrode technique, the oxygen reduction reaction in 0.1M KOH was studied at various micromesoporous carbide derived carbon powders, synthesized from various binary metal carbides. The catalytic activity and mechanism noticeable depends on the hierarchical structure of the nanoporous carbon electrode. The activation with CO2 increases the differential volume of pores and proportion of mesopores in carbon matrix. It was shown that the partially graphitized carbon C(Mo2C) with a large number of edge plane sites has higher electrocatalytic activity toward oxygen reduction in alkaline media compared with other amorphous or partly graphitized carbons studied. The corresponding relative catalytic activity of catalysts increases in the following order: C(WTiC2) < Vulcan < C(TiC) < C(TiC)-A1 ≤ C(TiC)-A2 < C(Mo2C)-A < C(Mo2C).

Oxygen Reduction in Alkaline Media: From Mechanisms to Recent Advances of Catalysts

The oxygen reduction reaction (ORR) is an important electrode reaction for energy storage and conversion devices based on oxygen electrocatalysis. This paper introduces the thermodynamics, reaction kinetics, reaction mechanisms, and reaction pathways of ORR in aqueous alkaline media. Recent advances of the catalysts for ORR were extensively reviewed, including precious metals, nonmetal-doped carbon, carbon–transition metal hybrids, transition metal oxides with spinel and perovskite structures, and so forth. The applications of those ORR catalysts to zinc–air batteries and alkaline fuel cells were briefly introduced. A concluding remark summarizes the current status of the reaction pathways, advanced catalysts, and the future challenges of the research and development of ORR.

Investigation of oxygen reduction in alkaline media on electrocatalysts prepared by the mechanical alloying of Pt, Co, and Ni

Pt, PtCo, and PtNi electrocatalysts were prepared by mechanical alloying, and their activity for oxygen reduction reaction in 0.5 M KOH was investigated using cyclic voltammetry (CV) and rotating ring-disk electrode techniques. Electrocatalysts were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Physical characterization showed that all electrocatalysts are alloys in the form of agglomerated particles that consist of nanocrystals. To perform an electrocatalytic evaluation, polarization curves, Koutecky–Levich and Tafel plots were obtained to calculate the kinetic parameters. Additionally, the molar fraction of the generated HO2 − and the number of transferred electrons were determined. PtCo alloy showed a better performance for oxygen reduction reaction with a higher exchange current density, a lower overpotential, as well as higher specific and mass activities due to a synergistic effect between Pt and Co atoms as a result of the alloying process.

Platinum-Dysprosium Alloys for Oxygen Reduction in Alkaline Media

Oxygen reduction reaction (ORR) has become one of the most studied electrochemical reactions due to its fundamental complexity and great importance in practical applications [1]. Specifically, different renewable energy technologies, including metal-air batteries and fuel cells (FCs) [2], are based on this reaction. Direct borohydride fuel cells use alkaline sodium borohydride solution as fuel and oxygen as the oxidant. The mechanism of the ORR is primarily determined by the electrode material and electrolyte solution. Recently, bimetallic alloys of Pt or Pd with rare earth (RE) metals scandium (Sc) or yttrium (Y) were suggested as novel electrocatalysts for the ORR based on density functional theory calculations [3]. Electrochemical measurements have confirmed improved activity of polycrystalline Pt3Sc and Pt3Y electrodes in comparison with pure Pt by a factor of 1.5 - 1.8 and 6 - 10, respectively, in the range 0.9 - 0.87 V. Herein, platinum-dysprosium (Pt-Dy) alloys, with different amounts of RE metal (50 to 60 at.%) were prepared by arc-melting starting from the stoichiometric amounts of the two metals and their composition and structure were characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. Subsequently, electrocatalytic activity for the ORR of Pt-Dy alloy electrodes was studied in alkaline solution by cyclic voltammetry (CV) and chronoamperometry (CA). Main kinetic parameters, namely charge transfer coefficient and number of electrons exchanged, were evaluated for temperatures ranging from 25 to 65 ºC. Furthermore, electrocatalytic activity for the ORR was studied in the presence of sodium borohydride in the supporting electrolyte in order to simulate conditions in direct borohydride fuel cells where borohydride crossover is possible to occur.

Optimized electrospinning synthesis of iron–nitrogen–carbon nanofibers for high electrocatalysis of oxygen reduction in alkaline medium

To achieve iron–nitrogen–carbon (Fe–N–C) nanofibers with excellent electrocatalysis for replacing high-cost Pt-based catalysts in the cathodes of fuel cells and metal-air batteries, we have investigated and evaluated the effects of polyacrylonitrile (PAN) concentration and the proportion of iron to PAN, along with voltage and flow rate during the electrospinning process, and thus proposed three criteria to optimize these parameters for ideal nanofiber catalysts. The best half-wave potential of an optimized catalysts is 0.82 V versus reversible hydrogen electrode in an alkaline medium, which reaches the best range of the non-precious-metal catalysts reported and is very close to that of commercial Pt/C catalysts. Furthermore, the electron-transfer number of our catalysts is superior to that of the Pt/C, indicating the catalysts undergo a four-electron process. The durability of the optimized Fe–N–C nanofibers is also better than that of the Pt/C, which is attributed to the homogeneous distribution of the active sites in our catalysts.

Electrocatalytic activity of alkyne-functionalized AgAu alloy nanoparticles for oxygen reduction in alkaline media.

1-Dodecyne-functionalized AgAu alloy nanoparticles were synthesized by chemical reduction of metal salt precursors at varied initial feed ratios. Transmission electron microscopic measurements showed that the nanoparticles were all rather well dispersed with the average core diameter in the narrow range of 3 to 5 nm. X-ray photoelectron spectroscopic studies confirmed the formation of AgAu alloy nanoparticles with the gold concentration ranging from approximately 25 at% to 55 at%. Consistent results were obtained in UV-vis spectroscopic measurements where the nanoparticle surface plasmon resonance red-shifted almost linearly with increasing gold concentrations. The self-assembly of 1-dodecyne ligands on the nanoparticle surface was manifested in infrared spectroscopic measurements. Importantly, the resulting nanoparticles exhibited apparent electrocatalytic activity for oxygen reduction in alkaline media, and the performance was found to show a volcano variation in the Au content in the alloy nanoparticles, with the best performance observed for the samples with ca. 35.5 at% Au. The enhanced catalytic activity, as compared to pure Ag nanoparticles or even commercial Pt/C catalysts, was accounted for by the unique metal-ligand interfacial bonding interactions as well as alloying effects that increased metal-oxygen affinity.

Tailored gold nanostructure arrays as catalysts for oxygen reduction in alkaline media and a single molecule SERS platform.

Although plenty of functional nanomaterials are widely applied in science and technology, cost-efficient, controlled and reproducible fabrication of metallic nanostructures is a considerable challenge. Automated electrorefining by scanning electrochemical microscopy (SECM) provides an effective approach to circumvent some drawbacks of traditional homogeneous syntheses of nanoparticles, providing precise control over the amount, time and place of reactant delivery. The precursor is just a raw metal, which is the most economically viable source. This approach ensures reproducibility and the opportunity for fabrication of micropatterns, which can be rapidly analyzed by scanning probe techniques. Here, a cost-effective methodology for the preparation of naked (ligand-free) metallic nanostructures, from polycrystalline gold using a moving microelectrode, is presented. Automated micropatterning of bare gold on indium tin oxide (ITO) demonstrates the versatility of this method to tune the size and shape of the nanostructures. The morphology of the obtained materials and thus their catalytic and plasmonic properties can be tuned using the electrorefining parameters. Programmable fabrication of sample microarrays by microprinting followed by comparative SECM studies or spectroscopic analysis allows quick optimization and characterization for specific purposes. Electrocatalytic oxygen reduction in alkaline media and surface-enhanced Raman spectroscopy (SERS) of single porphycene molecules are presented as model examples.

Carbon nanotubes-gold nanohybrid as potent electrocatalyst for oxygen reduction in alkaline media.

A carbon nanotube-gold nanohybrid was used as catalyst for the reduction of molecular oxygen in acidic and alkaline media, the relevant cathode reaction in fuel cells. In alkaline medium, the nanohybrid exhibits excellent activity with a dominant 4e(-) reduction of O2 and low overpotential requirement compared to previously reported nano-gold materials. This property is linked to its capability to efficiently mediate HO2(-) dismutation.

Defective TiO2-supported Cu nanoparticles as efficient and stable electrocatalysts for oxygen reduction in alkaline media.

Nanocomposites based on TiO2-supported copper nanoparticles were prepared by a hydrothermal method where copper nanoparticles with or without the passivation of 1-decyne were chemically grown onto TiO2 nanocolloid surfaces (and hence denoted as CuHC10/TiO2 and Cu/TiO2, respectively). Transmission electron microscopy measurements showed that the size of the hybrid nanoparticles was 5-15 nm in diameter with clearly defined lattice fringes for anatase TiO2(101) and Cu(111). The formation of anatase TiO2 nanoparticles was also observed by X-ray diffraction measurements. FTIR measurements confirmed successful attachment of alkyne ligands onto the surface of the copper nanoparticles via Cu-C≡ interfacial bonds in CuHC10/TiO2. XPS measurements suggested the formation of CuO in both samples with a higher concentration in Cu/TiO2, and interestingly Ti(3+) species were found in CuHC10/TiO2 but were absent in Cu/TiO2 or TiO2 nanoparticles. Electrochemical studies demonstrated that both Cu/TiO2 and CuHC10/TiO2 exhibited a markedly improved electrocatalytic performance in the oxygen reduction reaction, as compared to TiO2 nanocolloids alone, in the context of the onset potential, the number of electrons transferred and the kinetic current density. Importantly, among the series, CuHC10/TiO2 exhibited the best ORR activity with a high current density, an almost four-electron reduction pathway and long-term stability after 4000 cycles at high potentials, which may be ascribed to the defective TiO2 structures in combination with surface ligand engineering.

Pd/Ti Electrocatalyst in Technological Significance Reactions

New materials operating as future electrocatalysts into fuel cells or in environmental remediation processes are continuously under research. Here we studied palladium modified electrodes, such as Pd/Ti and Pd/GC (glassy carbon), which are electrochemically built and used in chromate detection, in oxygen reduction and alcohols oxidation reaction. The palladium material electrodeposited at constant potential was characterized by X-ray diffraction, and scanning electron microscopy. The response of Pd/Ti nanoelectrodes, by oxygen reduction was observed in alkaline and acid supporting electrolytes. The diffusion coefficient of 2 10-5 cm2/s with a transference of 4e -in 0.1M H2SO4 solution was calculated. A higher coefficient value in 0.05M NaOH was evaluated, because Ti substrate is also active in oxygen reduction in alkaline media. The reduction of Cr(VI) with Pd/Ti electrode proceeds at +0.58V vs Ag/AgCl in H2SO4 0.1M, with a diffusion coefficient of 2.210-5 ±0.01 cm2/s and a linear range between 0.019 -0.69mM Cr(VI). The lowest sensitivity 0.5μM Cr(VI) was determined with Pd/Ti electrode in the range permissible by drinking water of 1μМ⋅ The oxidation of alcohol molecules in alkaline environment showed by Tafel curves, the activity order on Pd/Ti electrocatalyts is ethanol≅n-propanol >ethylene glycol. The calibration curve obtained by anodic peak current density of cyclic voltammetries upon an increasing alcohol concentration (3 to 90mM alcohol) in NaOH 0.05M, permitted to evaluate an activity of PdTi(+0.1V)≈PdTi(-0.3V)>PdTi(-0.9V). The performance of Pd/Ti electrocatalysts was better when compared with a modified Pd/GC electrocatalyst, in the studied reactions.

New approach of nitrogen and sulfur-doped graphene synthesis using dipyrrolemethane and their electrocatalytic activity for oxygen reduction in alkaline media

We have been prepared a series of heteroatoms (N and/or S) doped graphene in different ratios from various doping precursors (pyridine, thiophene and bithiophene combined separately with dipyrrolemethane and used as single N and/or S precursor) by thermal reaction. The as synthesized heteroatoms-doped graphene materials have also been characterized via transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The XPS and Raman investigations suggest a better dual-doping with higher conversion rate of graphitic-N and thermal reduction of oxygen into the graphene sheets. The electrochemical investigation reveals that the both N and S-doped graphene (S1N2-GN800 and S2N2-GN800) have better catalytic activity on oxygen reduction reaction (ORR) than only N-doped graphene (N3-GN800) with the assistance of synergistic effect of dual-doping. Particularly, the high thermal treated final product, N and S dual-doped graphene (S2N2-GN1000) shows remarkable electrocatalytic activity towards the ORR which not only establishes a pathway of four-electron transfer reaction but also exhibits a better fuel selectivity and stability than that of commercially available 20wt% Pt/C electrode.

Chicken bone-derived N-doped porous carbon materials as an oxygen reduction electrocatalyst

In this work, a low-cost, N-doped, porous carbon material with high surface area is synthesized by carbonizing chicken bones. The N-doped porous carbon material has high specific surface area. Brunauer-Emmett-Teller (BET) surface area of obtained carbon material is ca. 769m2g−1 with a pore size distribution in the range of 1–4nm. Compared to a commercial Pt/C (10 wt%) catalyst, oxygen reduction in alkaline medium on the synthesized carbon material exhibits comparable electrocatalytic activity, long term-operating durability and excellent CH3OH tolerance, rendering it as a potential alternative to Pt-based catalysts.

Nitrogen self-doped porous carbon from surplus sludge as metal-free electrocatalysts for oxygen reduction reactions.

Nitrogen self-doped porous carbon was prepared by calcination treatment of surplus sludge, a toxic byproduct from microbial wastewater treatments, and exhibited a mesoporous structure, as manifested in scanning and transmission electron microscopic measurements. Nitrogen adsorption/desorption studies showed that the porous carbon featured a BET surface area as high as 310.8 m(2)/g and a rather broad range of pore size from 5 to 80 nm. X-ray photoelectron spectroscopic studies confirmed the incorporation of nitrogen into the graphitic matrix forming pyridinic and pyrrolic moieties. Interestingly, the obtained porous carbon exhibited apparent electrocatalytic activity in oxygen reduction in alkaline media, with the optimal temperatures identified within the range of 600 to 800 °C, where the number of electron transfers involved in oxygen reduction was estimated to be 3.5 to 3.7 and the performance was rather comparable to leading literature results as a consequence of deliberate engineering of the graphitic matrix by nitrogen doping.

Carbide Derived Carbon as a Possible Catalyst Support for PEMFC

During last ten years various carbides have been used as raw material for synthesis of micromesoporous carbons with exact pore size distribution. It has been recognized that, depending on the heat-treatment temperatures, different carbon materials exhibit different properties, such as surface area, porosity, electrical conductivity and cathodic oxygen electroreduction activity [1-4].In addition, an intensive research has focused on the development of electrocatalyst for the oxygen electroreduction reaction (ORR) because in a PEM fuel cell, the major limit on performance is the slow cathodic oxygen electroreduction process[5-7].The main aim of this work was to investigate the behavior of the micromesoporous carbon supports, prepared from WTiC2, TiC, Mo2C using chlorination process at various temperatures from 750°C to 1100°C (with specific surface area 360 m2g-1, 880 m2g-1 and 2020 m2g-1, respectively), as a electrocatalysts for the ORR [1,2,8,9] and to analyze ORR kinetics in 0.1 M KOH solution. For comparison commercially available VulcanXC72®was also used.Raman spectroscopy, XRD, SEM-EDX, HRTEM methods were applied for structural and electronic characterization of the materials [8,9]. Gas adsorption at liquid nitrogen temperature was used for the porosity analysis of the materials under discussion.The electrochemical measurements were carried out in a three-electrode electrochemical cell. Several important reaction parameters, such as the number of electrons involved in the ORR, Tafel slopes, and the kinetic rate constant for the ORR, were obtained from the RDE measurements.Potentials were measured against Hg|HgO|0.1M KOH reference electrode. Rotating disc electrode (RDE) data were measured at rotation rates from 0 to 3000 rpm (potential scan rate v=10 mV∙s-1) and in the region of potentials from +0.21 to -0.75 V vs. Hg|HgO|0.1M KOH. Cyclic voltammograms were measured at potential scan rates (v mV/s) 5, 10, 20, 30, 50, 70, 100, 150 and 200, in the case of both Ar and O2saturated solution.Electrochemical data for unmodified micromesoporous carbon electrodes show that the catalytic ORR activity and mechanism noticeably depends on the porous structure of a carbon electrode, i.e. mainly on the micro/meso porosity and specific surface area of electrode under study.C(Mo2C) showed two times higher activity compared to data reported in the literature [7] and somewhat more positive half-wave potential values compared with previously studied amorphous carbon materials. The Tafel plot for the C(Mo2C), is divided into two linear parts. It is also concluded that the partially graphitized carbon C(Mo2C) with a large number of edge plane sites has higher electrocatalytic activity towards oxygen reduction in alkaline media, compared with amorphous carbons studied previously [1-4]. Acknowledgements:This work was supported by the Estonian Centre of Excellence in Science Project TK117T "High-technology Materials for Sustainable Development", the Estonian Energy Technology Program project SLOKT 10209T, the Materials Technology project SLOKT12180T.

Chemically Modifying Electrodes in 3D

Carbon aerogels, nanofoams, nanofoam-filled carbon papers, and related ultraporous nanoarchitectures are attractive electrode materials for electrochemical sensing, catalysis, and energy storage/conversion applications because of their conductive carbon framework and inherent characteristics of high surface area and through-connected networks of porosity with tunable pore size. [1] These conductive nanoarchitectures serve as effective three-dimensional electrochemical interfaces, and enhance the performance of rate-critical devices, such as electrochemical capacitors and fuel cells. The principal limitation of such carbon nanoarchitectures is their lack of the electrochemical functionalities that are beneficial for faradaic charge-storage and electrocatalysis. To address this issue, we modify carbon nanoarchitectures to incorporate such functionalities as electroactive and ion-conducting polymers, [2] , [3] mixed-conducting metal oxides, [4] , [5] and specifically adsorbed noble-metal nanoparticles. [6] Unlike specialized nanostructured carbons (fullerenes, graphene, nanotubes), which although exist as a unit building block, all too often agglomerates when fabricated into an electrode structure, carbon nanoarchitectures are pre-assembled objects with in-built, co-continuous pore volume and solid scaffolding. Modifying the solid “walls” in such architectures introduces the complication of “painting” blind, i.e., without direct sight lines for precursor ingress. The critical step in generating controlled, non-line-of-sight, conformal polymer or oxide coatings within ultraporous, macroscale nanoarchitectures is the use of conditions where growth self-limits. A corollary benefit arises with conformal, self-limiting growth in that the starting 3D open pore structure remains through-connected.When starting with a conductive nanoarchitecture, electrochemistry offers remarkably effective modification protocols that satisfy the stringent conditions imposed by non-line-of-sight self-limiting growth. We rely on direct electrodeposition, electroless deposition, and specific adsorption to uniformly modify the interiors of carbon nanofoam papers even when they are as thick as 0.3 mm.Simply soaking carbon nanofoam papers in a solution containing a transition-metal oxidant (RuO4, MnO4 –, and FeO4 2–) yields conformal, nanometric oxide coatings that extend throughout the carbon-paper-supported nanofoam structure. [7] The redox reactions of the charge-storing oxide paint boost the energy density of the resulting hybrid nanoarchitectures for electrochemical capacitor applications, [8] , [9] , [10] catalyze oxygen reduction in alkaline media, such as when used as the air-breathing cathode in metal–air battery cells [11] or alkaline fuel cells, and offer a 3D platform to build all-solid-state 3D batteries.4 , [12] Electrocatalytic nanoarchitectures are also achieved by modifying carbon aerogels/nanofoams with thiophene functionalities that readily adsorb pre-formed metal nanoparticles (e.g., Pt, Pd, Ag, Au), resulting in an ultraporous electrode structure for fuel-cell applications. REFERENCES [1]. J.C. Lytle, J.M. Wallace, M.B. Sassin, A.J. Barrow, J.W. Long, J.L. Dysart, C.H. Renninger, M.P. Saunders, N.L. Brandell, and D.R. Rolison, Energy Environ. Sci. 4, 1913 (2011).[2]. J.W. Long, B.M. Dening, T.M. McEvoy, D.R. Rolison, J. Non-Cryst. Solids 350, 97 (2004).[3]. A.E. Fischer, T.M. McEvoy, J.W. Long, Electrochim . Acta 54, 2962 (2009).[4]. D.R. Rolison, J.W. Long, J.C. Lytle, A.E. Fischer, C.P. Rhodes, T.M. McEvoy, M.E. Bourg, and A.M. Lubers, Chem. Soc. Rev. 38, 226 (2009).[5] J.W. Long and D.R. Rolison, Acc. Chem. Res. 40, 854 (2007)[6]. W.S. Baker, J.W. Long, R.M. Stroud, and D.R. Rolison, J. Non-Cryst. Solids 350, 80 (2004).[7]. M.B. Sassin, C.N. Chervin, D.R. Rolison, and J.W. Long, Acc. Chem. Res. 46, 1062 (2013).[8]. A.E. Fischer, K.A. Pettigrew, R.M. Stroud, D.R. Rolison, and J.W. Long, Nano Lett. 7, 281 (2007).[9]. A.E. Fischer, M.P. Saunders, K.A. Pettigrew, D.R. Rolison, and J.W. Long, J. Electrochem. Soc. 155, A246 (2008).[10]. M.B. Sassin, A.N. Mansour, K.A. Pettigrew, D.R. Rolison, and J.W. Long, ACS Nano 4, 4505 (2010).[11]. C.N. Chervin, J.W. Long, N.L. Brandell, J.M. Wallace, and D.R. Rolison, J. Power Sources 20 7, 191 (2012).[12]. J.W. Long, B. Dunn, D.R. Rolison, and H.S. White, Chem. Rev. 1 04, 4463 (2004).

Materials for ORR Electrocatalysis: Catalytic Center and Substrate Effects

One of the most important challenges for polymer electrolyte membrane fuel cells (PEMFCs) in terms of facilitating its widespread commercial use is to improve the performance and durability of the electrocatalyst by developing novel catalysts (precious and non-precious catalytic centers) and support materials. One way to improve the oxygen reduction reaction (ORR) activity of Pt-based catalysts is to control Pt nanoparticles (Pt NPs) size, morphology and the dispersion onto substrates. Carbonyl chemical route for synthesizing Pt NPs facilitate a narrow particle size distributions (about 2-3 nm) [1], and homogeneous dispersion on different substrates [2,3]. A variety of carbon-based materials such as carbon nanotubes (CNT), graphite (HOPG), graphene, carbon nanohorns (CNH) and non-carbonaceous based materials, such as metal oxides (Titania, Yttria, Ceria, etc.,) [4,5] can be used as both catalyst and catalyst support materials. On the way to further explore the substrate effect on non-Pt electrocatalyst, CoSe2and CoO were supported on Carbon, CNH and nitrogen doped nanohorn (NCNH). The activity modulation in non-Pt catalysts was found to be strongly dependent on the morphology as well as the composition of substrate materials. The improved interaction of nitrogen species in NCNH and the metal centers modify the active reaction centers. This modified active reaction centers boost the catalytic activity with minimum overpotential for molecular oxygen reduction in alkaline medium (Figures 1a, b). Preliminary analysis indicates that this improved activity not only constrained in oxygen reduction but other catalytic reaction such as oxygen evolution reaction and hydrogen evolution reaction and further to an application on microfluidic fuel cells.AcknowledgementsAuthors acknowledge the partial support of the European Union’s Seventh Framework Programme (FP7/2007-2013) for the Fuel Cell and Hydrogen Joint Technology Initiative under grant agreement nr 303492 CathCat. SM U acknowledges the financial assistance through Raman-Charpak Fellowship, and JMMH acknowledges CONACyT fellowship. [1] N. Alonso-Vante, Fuel Cell, 2006, 6, 182-189.[2] J. Ma, A. S. Gago, W. Vogel, N. Alonso-Vante, Chemcatchem, 2013, 5, 701-705.[3] L. Timperman, Y.J. Feng, W. Vogel, N. Alonso-Vante, Electrochimica Acta, 2010, 55, 7558-7563.[4] Walter Vogel, Laure Timperman, Nicolas Alonso-Vante, Applied Catalysis A: General, 2010, 377, 167-173.[5] C.Liu , Y.Wei and K.Wang, Chem.Comm., 2010, 46, 2483-2485.