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Abstract: In this paper, the electrochemical reduction of oxygen has been studied on gold nanoparticle/multi-walled carbon nanotube (AuNP/MWCNT) modified glassy carbon (GC) electrodes in 0.5M H2SO4 using the rotating disk electrode (RDE) method. The AuNP/MWCNT catalysts were prepared by chemical deposition of AuNPs onto MWCNTs spontaneously grafted with 4-nitrophenyl groups. The composite electrode was characterised by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). The oxygen reduction behaviour of these electrodes was compared with that of a bulk gold electrode. The AuNP/MWCNT catalyst showed a pronounced electrocatalytic activity towards O2 reduction in acid media. The half-wave potential of O2 reduction on the AuNP/MWCNT catalyst shifted ca 80mV to more positive potentials as compared to that of a polished Au electrode. The kinetic parameters of oxygen reduction were determined and the specific activity of the hybrid electrode was slightly higher than that of the bulk Au electrode. [Copyright &y& Elsevier]

Abstract: The electrochemical response of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) on aryl-modified glassy carbon (GC) electrodes has been investigated. The electrochemical modification of GC surface with 4-nitrophenyl (NP) and 4-carboxyphenyl (CP) groups was performed using the diazonium reduction method. The 4-aminophenyl-modified GC electrodes were obtained by electroreduction of NP films. The surface coverage of aryl groups was altered by varying the number of potential scans during electrografting experiments. The electrochemical behaviour of ABTS was studied on bare and aryl-modified GC electrodes using cyclic voltammetry and the rotating disk electrode (RDE) methods. Electrochemical measurements were performed in acetate and phosphate buffers (pH=4–8) to study the effect of pH on the electron transfer process. The response of ABTS was independent of pH for bare GC and GC/NP electrodes (modified by 20 electrografting scans), whereas a slight pH-dependence was observed for other electrodes. The strongest blocking action was observed for the NP-modified GC electrodes of higher surface coverage and the lowest for reduced NP films (modified by a single electrografting scan). [Copyright &y& Elsevier]

Nitrogen-doped graphene oxide supported silver nanoparticles (Ag/NGO) have been synthesised using three different methods. The prepared catalysts were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electrochemically tested for oxygen reduction reaction (ORR) in alkaline solution. The Ag/NGO catalysts prepared by borohydride reduction showed the least degree of nanoparticle agglomeration and the material which was prepared using ascorbic acid yielded the biggest Ag particles. XPS revealed that the nitrogen to carbon atomic ratio was about 0.07 and EDS mapping showed that nitrogen was uniformly distributed over the graphene. The ORR on all the Ag/NGO catalysts proceeded via 4-electron pathway yielding water while on the support material, N-doped graphene oxide, the number of electrons transferred per O 2 molecule was lower than four. The mass activity of all Ag/NGO catalysts was determined to be at least twice higher than that of NGO. [ABSTRACT FROM AUTHOR]

In this work the electrocatalysis of oxygen reduction on iron and cobalt phthalocyanine modified reduced graphene oxide/multi-walled carbon nanotube (rGO/MWCNT) composite catalyst has been investigated. Modification of the carbon support was achieved by pyrolysing the mixture of rGO/MWCNT in the presence of metallophthalocyanine compounds at 800 °C. The surface morphology, graphitisation and surface composition of the catalyst materials were characterised by transmission electron microscopy (TEM), scanning electron microscopy (SEM), micro-Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The oxygen reduction reaction (ORR) was studied in 0.1 M KOH and 0.5 M H 2 SO 4 solutions on glassy carbon electrodes modified with MN 4 -macrocycle/rGO/MWCNT catalysts employing the rotating disk electrode (RDE) method. The RDE results show that both iron and cobalt phthalocyanine modified rGO/MWCNT electrocatalysts are highly active for ORR in alkaline solution while in acid media these materials exhibit only modest ORR activity. [ABSTRACT FROM AUTHOR]

Abstract: The electrochemical reduction of oxygen was studied on vacuum evaporated thin Pt films (0.25–20nm thick) on polycrystalline Au substrate (Pt/Au) in 0.1M HClO4 and 0.05M H2SO4 solutions using the rotating disk electrode (RDE) method. The surface morphology of Pt films was examined by scanning tunnelling microscopy (STM). The O2 reduction specific activity of Pt films increased with increasing the film thickness in HClO4, but was lower than that of bulk Pt even for the thickest films. In H2SO4, the specific activity showed no significant dependence on the platinum loading and was lower than in HClO4. The Tafel slope values characteristic to polycrystalline Pt (−120mVdec−1 and −60mVdec−1) were found for all electrodes. The RRDE studies of 0.5nm Pt/Au electrode revealed that O2 reduction predominantly proceeds through 4e− pathway and H2O2 is produced in low quantities. [Copyright &y& Elsevier]