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Innovations in energy storage and conversion technologies are closely dependent on developing superior materials that can be used in this field. Here, we present an industrially scalable and low-cost solvothermal method for synthesizing Si-N-co-doped (Si-N-GN) and N-doped graphene (N-GN) with a high specific surface area of 523 m2 g−1 and 1289 m2 g−1, respectively. Silicon atoms were successfully incorporated into the 2D graphene at a doping rate of 2.28 at.% via Si-C, Si-N, and Si-O bonds, thanks to the decarbonylation of N,N-dimethyl formamide (DMF) into dimethylamine and highly reactive carbonyl at the solvothermal conditions. The Si-N-GN exhibited an average electron transfer number of 3.83 e− per mole of O 2 in a wide potential range with similar on-set potential (0.988 V vs. 1.012 V), greater methanol tolerance capability, and higher diffusion limiting current density (7.2 vs. 6.5 mA cm−2 at 0.4 V) for oxygen reduction reaction (ORR) in alkaline electrolytes compared to the commercial Pt/C catalyst. The improved ORR performance of Si-N-GN was attributed to the effectively decreased adsorption energy of O 2 on SiC 4 and SiN 1 C 3 type bondings supported by the density functional theory (DFT) calculations based on the model created according to the XPS results. The promising electrocatalytic activity of Si-N-GN for ORR could also be enlarged to other electrochemical applications, including metal-air batteries. [Display omitted] • Nitrogen-doped and silicon-nitrogen co-doped graphene can be produced by a scalable procedure. • SiC 4 and SiN 1 C 3, as new active centers on graphene, promote the ORR activity close to Pt/C. • Silicon-nitrogen co-doped graphene is a promising candidate material for electrochemical technologies. [ABSTRACT FROM AUTHOR]

Pt-Pd catalyst supported on nitrogen-doped carbon nanofiber (N-CNF) was prepared and evaluated as a cathode electrode of the direct methanol fuel cell (DMFC). The N-CNF, which was directly synthesized by the catalytic chemical vapor deposition from acetonitrile at 640° C, was verified as having a change of electrochemical surface properties such as oxygen reduction reaction (ORR) activities and the electrochemical double layer compared with common carbon black (CB). To attain the competitive oxygen reduction reaction activity with methanol tolerance, the Pt and Pd metals were supported on the CB or the N-CNF. The physical and electrochemical characteristics of the N-CNF-supported Pt-Pd catalyst were examined and compared with catalyst supported on the CB. In addition, DMFC single cells using these catalysts as the cathode electrode were applied to obtain I-V polarization curves and constant current operating performances with high-concentration methanol as the fuel. Pt-Pd catalysts had obvious ORR activity even in the presence of methanol. The higher power density was obtained at all the methanol concentrations when it applied to the membrane electrode assembly (MEA) of the DMFC. When the N-CNF is used as the catalyst support material, a better performance with high-concentration methanol is expected. [ABSTRACT FROM AUTHOR]

It has been suggested that the presence of adsorbed impurities, such as capping agent or organic reaction products adsorbed on the metallic nanoparticles, severely affects the electrocatalytic activity of surface sensitive reactions. At least in some cases, these adsorbed impurities may alter the electronic nature of nanoparticles and thus alter the electrocatalytic activity. In this work, we report the synthesis of AuPt/C bimetallic nanoparticles (BNPs) supported on Vulcan carbon using the polyol method in the presence of different concentrations of polyvinylpyrrolidone (0.01, 0.1, and 1 %) as a capping agent and electrocatalytic activity of the synthesized AuPt/C BNPs. We found that the PVP adsorbs on the AuPt BNPs through C = O functional group, but not through the N-atom. The oxygen reduction reaction (ORR) activity and the methanol tolerance were evaluated on those PVP adsorbed AuPt/C BNPs catalysts. Remarkably, AuPt/C BNPs catalyst with 0.1 % PVP showed a balance of ORR electrocatalysis and methanol tolerance when compared to the PVP free AuPt BNPs. The adsorbed PVP on AuPt BNPs alters the electronic properties of the Pt through electronic interaction with Pt and also controls the surface geometry suitable to ORR, but not the methanol adsorption. [ABSTRACT FROM AUTHOR]

Abstract: Nitrogen-doped metal free carbon catalysts were prepared via pyrolysis of polyaniline-coated carbon in different ratios with varying nitrogen content. The surface states and surface composition were investigated using XPS (X-ray photoelectron spectroscopy). XPS analysis confirms the presence of pyridinic and pyrollic nitrogen in the carbon network that is responsible for the oxygen reduction activity. The shift in onset potential of oxygen reduction on C:N (1:1) is ∼0.3V more positive compared to Vulcan carbon, shows improved activity toward oxygen reduction reaction in acidic electrolyte. Hydrodynamic voltammetric studies confirm that the reduction of oxygen follows the 4e− pathway which leads to the formation of water. [Copyright &y& Elsevier]

The oxygen reduction activity and methanol tolerance of Pt–Bi/C electrocatalysts were studied using electrochemical voltammetric techniques including rotating ring-disk electrode. The Pt–Bi/C catalyst was prepared via a polyol method and subjected to heat treatment to increase the degree of alloying. X-ray diffraction studies revealed the unalloyed character of the as-prepared catalyst and alloy formation upon heat treatment. The electrochemical behaviour of both catalysts showed different behaviour in dilute acid electrolytes, namely sulphuric and perchloric acids. In both electrolytes, the oxygen reduction reaction was found to occur via the four-electron process revealing that the mechanism of oxygen reduction is unaltered even in the presence of excess of methanol. Pt–Bi/C catalyst material showed dramatically different properties and reactivity with respect to oxygen reduction activity and methanol tolerance in perchloric and sulphuric acids. The onset potential for oxygen reduction reaction (ORR) significantly shifted by about 100 mV to more negative values and at the same time the current density was significantly enhanced. This type of non-ideal methanol-tolerant behaviour among Pt bimetallics and a “trade off” is common with all the known so-called methanol tolerant combinations of Pt. In general, the Pt–Bi surface appeared to have a negligibly lesser sensitivity towards methanol activity compared to pure platinum. [ABSTRACT FROM AUTHOR]

Abstract: Carbon-supported Pt–Sn/C bimetallic nanoparticle electrocatalysts were prepared by the simple reduction of the metal precursors using ethylene glycol. The catalysts heat-treated under argon atmosphere to improve alloying of platinum with tin. As-prepared Pt–Sn bimetallic nanoparticles exhibit a single-phase fcc structure of Pt and heat-treatment leading to fcc Pt75Sn25 phase and hexagonal alloy structure of the Pt50Sn50 phase. Transmission electron microscopy image of the as-prepared Pt–Sn/C catalyst reveals a mean particle diameter of ca. 5.8nm with a relatively narrow size distribution and the particle size increased to ca. 20nm when heat-treated at 500°C due to agglomeration. The electrocatalytic activity of oxygen reduction assessed using rotating ring disk electrode technique (hydrodynamic voltammetry) indicated the order of electrocatalytic activity to be: Pt–Sn/C (as-prepared)>Pt–Sn/C (250°C)>Pt–Sn/C (500°C)>Pt–Sn/C (600°C)>Pt–Sn/C (800°C). Kinetic analysis reveals that the oxygen reduction reaction on Pt–Sn/C catalysts follows a four-electron process leading to water. Moreover, the Pt–Sn/C catalyst exhibited much higher methanol tolerance during the oxygen reduction reaction than the Pt/C catalyst, assessing that the present Pt–Sn/C bimetallic catalyst may function as a methanol-tolerant cathode catalyst in a direct methanol fuel cell. [Copyright &y& Elsevier]

A carbon-supported Pd-based PdPt catalyst (PdPt/C) with a small amount of Pt was prepared by borohydride reduction method and its activity in the oxygen electro-reduction reaction (ORR) was investigated in acidic conditions both with and without methanol. For comparison, carbon-supported Pt (Pt/C) and Pd (Pd/C) catalysts were prepared and the ORR activities were compared. Results revealed that the PdPt/C catalyst showed slightly lower ORR activity in terms of onset potential of oxygen reduction than Pt/C catalyst in 0.1M HClO4. However, PdPt/C catalyst exhibited enhanced activity toward selective ORR with methanol-tolerant characteristics in 0.1M HClO4 in the presence of methanol. The PdPt/C catalyst prepared here is suitable for use as a cathodic electrocatalyst in direct alcohol fuel cells after addition of small amount of expensive Pt metal. [ABSTRACT FROM AUTHOR]

We synthesized a novel nonprecious metal electrocatalyst by pyrolysis of a colloid mixture consisting of a tungsten source and phenolic resin, with the simultaneous addition of ferric salt. The rationally designed electrocatalyst has a unique structure, with nanosized WC and Fe 3 W 3 C uniformly dispersed in a three-dimensional porous carbon framework. WC, which was thought difficult to produce, is successfully prepared at a relatively low temperature of about 750 °C at an inert atmosphere. XRD studies demonstrate the self-assisted effect of Fe, which accelerates the formation of WC, getting around the pathway of direct carbonaceous reduction of tungsten by carbon. The porous iron-tungsten carbide (Fe-W-C) nanocomposite as electrocatalyst shows excellent ORR activity with the onset and half-wave potentials of 0.864 and 0.727 V (vs RHE), respectively, which are close to those of Pt/C (0.976 and 0.820 V vs RHE). Electrochemical measurements show that Fe-W-C follows almost the effective four-electron-transfer pathway and would not be disturbed by methanol. The presence of a protective graphite shell outside the active carbide cores substantially improves the durability of the electrocatalyst. Both the removal of Fe species and the absence of W species would severely degrade the activity, while halide ions Cl - and sulfur-containing species SCN - can significantly suppress the ORR activity by the blocking of Fe species. These facts indicate that the ORR active species of Fe-W-C should be relevant to both W and Fe species.