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Abstract: For the first time, the oxygen reduction reaction (ORR) is studied on pyrolysed electrospun multi-walled carbon nanotube (MWCNT) and styrene-acrylonitrile (SAN) composite fibre catalysts in alkaline medium. Scanning electron microscopy images revealed that the prepared catalysts mainly consist of MWCNTs, while nitrogen doping of the catalysts is confirmed by X-ray photoelectron spectroscopy. This indicates that SAN can be used as a nitrogen precursor. The ORR studies carried out by rotating disc electrode (RDE) and rotating ring-disc electrode (RRDE) methods showed that the prepared catalysts were considerably more active towards the ORR than the pristine MWCNTs.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Thin Pd coatings were obtained on glassy carbon electrodes by galvanically replacing the electron beam-deposited copper layers with palladium. The prepared electrodes were studied by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The electrodes were electrochemically tested for oxygen reduction reaction (ORR) employing the rotating disc electrode (RDE) method in alkaline solution. The remaining copper was detected for two of the thickest (5 and 10 nm) sacrificial Cu layers using energy-dispersive X-ray spectroscopy (EDX). SEM images of thin Pd films showed some larger particle growth for all the studied film thicknesses, but spherical particles such as those achieved for example by the electron beam evaporation method were not visible. Specific activity of the electrodes for O2 reduction did not depend on the thickness of the sacrificial copper layer. The O2 reduction reaction followed a four-electron pathway with a mechanism similar to that of commercial Pd/C, where the first electron transfer to the O2 molecule is the rate-determining step.ᅟ [ABSTRACT FROM AUTHOR]

This paper deals with nitrogen-doped graphene nanosheets prepared using dicyandiamide precursor as a catalyst support for oxygen reduction reaction (ORR). Platinum nanoparticles supported on N-doped graphene nanosheets (Pt/NG) were studied as electrocatalysts for ORR in acid and alkaline solutions employing the rotating disk electrode (RDE) technique. Pt/NG nanomaterials were synthesised by chemical reduction of hexachloroplatinic acid using sodium borohydride or ethylene glycol as reducing agents. Surface morphology and composition of the prepared catalysts were examined by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The TEM images showed a high dispersion of Pt nanoparticles on N-doped graphene nanosheets due to strong interaction of Pt with nitrogen functionalities. The average nitrogen content was between 6 and 7 at.% according to the XPS analysis. In acidic solution, 20 wt% Pt/NG catalyst prepared by borohydride reduction showed the highest specific activity for O reduction from all the Pt/NG materials studied. Pt/NG nanomaterials exhibited excellent electrocatalytic activity in alkaline media, and their half-wave potentials were similar to that of commercial Pt/C catalyst. The RDE data analysis showed that the ORR on the Pt/NG catalysts proceeded via four-electron pathway. [ABSTRACT FROM AUTHOR]

Manganese phthalocyanine (MnPc) and copper phthalocyanine (CuPc)-modified electrodes were prepared using multi-walled carbon nanotubes (MWCNTs) as a support material. The catalyst materials were heat treated at four different temperatures to investigate the effect of pyrolysis on the oxygen reduction reaction (ORR) activity of these electrocatalysts. The MWCNT to metal phthalocyanine ratio was varied. Scanning electron microscopy (SEM) was employed to visualise the surface morphology of the electrodes and the x-ray photoelectron spectroscopic (XPS) study was carried out to analyse the surface composition of the most active catalyst materials. The ORR was studied in 0.1 M KOH solution employing the rotating disk electrode (RDE) method. Glassy carbon (GC) electrodes were modified with carbon nanotube-supported metal phthalocyanine catalysts using Tokuyama AS-4 ionomer. The RDE results revealed that the highest electrocatalytic activity for ORR was achieved upon heat treatment at 800 °C. CuPc-derived catalyst demonstrated lower catalytic activity as compared to the MnPc-derived counterpart, which is in good agreement with previous literature, whereas the activity of MnPc-based catalyst was higher than that reported earlier. [ABSTRACT FROM AUTHOR]

The electrocatalytic activity of electrodeposited palladium-gold (PdAu) alloys towards the oxygen reduction reaction (ORR) was studied in 0.05 M HSO and 0.1 M KOH solutions using the rotating disc electrode (RDE) method. The electrochemical deposition was carried out at a constant potential and the ratio of concentrations of the precursors in the deposition bath was varied. The surface morphology of the deposits was studied using scanning electron microscopy (SEM), and the average particle size for PdAu alloys was determined to be about 6 nm. The X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV) studies suggest that the resulting PdAu coatings are alloyed. The ORR activities of the electrodes were compared by calculating the specific activities on the basis of the real electroactive surface area of Pd. The specific activity did not depend on the composition of the alloy in sulphuric acid solution, but in alkaline medium it increased with decreasing Pd content. [ABSTRACT FROM AUTHOR]

The electrochemical properties of Au electrodes grafted with 4-nitrophenyl and 4-decylphenyl groups have been studied. The electrografting of gold electrode surface with aryl groups was carried out by electroreduction of the corresponding diazonium salts in acetonitrile. The nitrophenyl film growth on gold was examined by atomic force microscopy, electrochemical quartz crystal microbalance and X-ray photoelectron spectroscopy. These measurements showed that a multilayer film of nitrophenyl groups was formed. Cyclic voltammetry was used to study the blocking properties of aryl-modified gold electrodes towards the Fe(CN) redox system. The reduction of oxygen was strongly suppressed on these electrodes as evidenced by the rotating disc electrode results. [ABSTRACT FROM AUTHOR]

The resistive response of atomic layer deposited thin epitaxial α-Cr2O3(0 0 1) films, to H2 and CO in air, was studied. The films were covered with Pt nanoislands formed by electron-beam evaporation of a sub-monolayer amount of the material. The gas measurements were performed at 250°C and 450°C. These temperatures led to different proportion of chemical states, Pt2+ and Pt4+, to which the Pt oxidized. The modification was ascertained by the X-ray photoelectron spectroscopy method. As a result of the modification, the response was fast at 250°C, but slowed at 450°C. A disadvantageous abundance of Pt4+ arising at 450°C in air could be diminished by high-vacuum annealing thus restoring the response properties of the system at 250°C. [ABSTRACT FROM AUTHOR]