N-doped carbon, a promising alternative to Pt catalyst for oxygen reduction reactions (ORRs) in acidic media, is modified in order to increase its catalytic activity through the additional doping of B and P at the carbon growth step. This additional doping alters the electrical, physical, and morphological properties of the carbon. The B-doping reinforces the sp(2)-structure of graphite and increases the portion of pyridinic-N sites in the carbon lattice, whereas P-doping enhances the charge delocalization of the carbon atoms and produces carbon structures with many edge sites. These electrical and physical alternations of the N-doped carbon are more favorable for the reduction of the oxygen on the carbon surface. Compared with N-doped carbon, B,N-doped or P,N-doped carbon shows 1.2 or 2.1 times higher ORR activity at 0.6 V (vs RHE) in acidic media. The most active catalyst in the reaction is the ternary-doped carbon (B,P,N-doped carbon), which records -6.0 mA/mg of mass activity at 0.6 V (vs RHE), and it is 2.3 times higher than that of the N-doped carbon. These results imply that the binary or ternary doping of B and P with N into carbon induces remarkable performance enhancements, and the charge delocalization of the carbon atoms or number of edge sites of the carbon is a significant factor in deciding the oxygen reduction activity in carbon-based catalysts.

Binary and Ternary Doping of Nitrogen, Boron, and Phosphorus into Carbon for Enhancing Electrochemical Oxygen Reduction Activity

A new strategy for enhancing the oxygen reduction reaction (ORR) activity of carbon-based catalysts in acidic media is proposed and characterized; the strategy consists in modifying the ORR through dual doping of nitrogen and phosphorus into the carbon. The P, N-doped carbon is prepared via pyrolysis of a mixture composed of dicyandiamide (DCDA), phosphoric acid, cobalt chloride, and iron chloride at 900 °C under an Ar atmosphere. The P-doping induces an uneven surface with many open edged sites in the carbon morphology and increases the carbon surface area from 108.1 to 578.8 m2 g−1. The XRD, XPS-C1s, and Raman spectroscopy results reveal that the crystallinity and degree of the sp2-carbon network decrease and the number of defect sites of the carbon increase as the amount of P-doping increases. All catalysts demonstrated similar proportions of N-doping types regardless of the P-doping amount: pyridinic-N and graphitic-N were dominant phases in the carbon lattice. In the ORR, the onset potential of the prepared catalysts was 0.6 V (vs. Ag/AgCl) in 1 M HClO4. The N-doped carbon records −0.69 mA mg−1 of mass activity at 0.5 V (vs. Ag/AgCl), but additional P-doping results in an increase of activity (−2.88 mA mg−1) that is more than fourfold that produced without the additional P-doping. Moreover, additional P-doping also modifies the ORR pathway, as the N-doped carbon induces more than 10% of H2O2; however, the P, N-doped carbon produced below 4% of H2O2 during the ORR.

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Phosphorus–nitrogen dual doped carbon as an effective catalyst for oxygen reduction reaction in acidic media: effects of the amount of P-doping on the physical and electrochemical properties of carbon

We Show that pair hopping through a Kondo singlet give rise to a negative Josephson coupling. Thus, our calculation supports the existance of staggered pair correlations in the strong coupling limit of a one dimensional Kondo lattice.

Negative Josephson coupling in the Kondo strong coupling limit

DLC (Diamond-Like Carbon) coatings feature high hardness, good wear resistance and low friction. Applying DLC coatings to titanium alloys using different coating techniques can improve the surface properties. However, in many cases, this hard coating fails under mechanical loading due to the mechanical incompatibility of the coating and substrate. Therefore, an intermediate layer providing improved load support is necessary to prevent the failure of the DLC film. For this purpose, the Micro Arc Oxidation (MAO) and Closed Field Unbalance Magnetron Sputtering (CFUBMS) coating techniques were used to deposit duplex MAO/DLC coating on Ti6Al4V (Grade 5) alloy. The surface topography, morphology, crystallographic structure and thickness of the duplex coatings were determined using Scanning Electron Microscopy (SEM), XRD and RAMAN. The hardness was measured using a nano-hardness tester. The hardness, adhesion to the substrate and load-bearing capacity of DLC increased due to the intermediate layer of TiO 2 deposited by MAO because it decreased the mechanical incompatibility between the soft substrate and hard coating. The duplex coating using the MAO/CFUBMS process was effective in maintaining a convenient, low, stable coefficient of friction and improving the tribological behaviour of the Ti6Al4V substrate. It was observed that the duplex coatings deposited on the Ti6Al4V substrate indicate a better tribological performance than the DLC or MAO coatings on the Ti6Al4V alloy substrate.

Wear and adhesion resistance of duplex coatings deposited on Ti6Al4V alloy using MAO and CFUBMS

Two dimensional graphene oxides converted to three dimensional P, N, F and B, N, F tri-doped graphene by ionic liquid for efficient catalytic performance

Yong S. Park

Papers

Structures and mechanical properties of diamond like carbon films prepared by closed-field unbalanced magnetron sputtering

Synthesis and mechanical properties of amorphous carbon films by closed-field unbalanced magnetron sputtering

Effect of the target power density on the synthesis and physical properties of sputtered nc-C films

Synthesis and mechanical properties of hydrogenated carbon and carbon nitride films prepared by magnetron sputtering