Oxygen electroreduction on chemically modified glassy carbon electrodes in alkaline solution

Low energy liquid plasma for direct reduction and formation of rGO-aminopyridine hybrid for electrical and environmental applications

The present works demonstrate the formation of reduced graphene oxide (r-GO) and aminopyridine (r-GO-(AmPy)_n) hybrid by submerged liquid plasma process. Raman spectra shows the ID/IG ratio of GO, r-GO and r-GO-(AmPy)_n are 2.2, 1.91 and 2.0, respectively. The decrease in ID/IG ratio of r-GO clearly indicate the reduction of oxygen functional groups and restoration of sp² network in r-GO domain. The pyridinic and pyrrolic functional group present in rGO-(AmPy)_n hybrids shows a distinct redox peaks in cyclic voltameter at the scan rates of 5, 10 and 25mV/s. The r-GO-(AmPy)_n hybrid displayed an excellent electrochemical performance with a high specific capacitance of 418, 400 and 381F/g at the current densities of 0.1, 0.2 and 0.3A/g, respectively. Electro chemical generation of H₂O₂ at the rGO-(AmPy)_n surface was evaluated and found to be 0.72mmol for the fixed reaction time of 60min. Similarly, conversion of H₂O₂ to OH radical with a coated Fe₃O₄ plate catalyst was found to be 0.15mmol. A H₂O₂/OH radicals generated in the electrochemical cell was used for the degradation of methyl parathion. During the degradation (7.5mg/L), two intermediates like methylparaoxon, and p-nitrophenol were identified by the Gas Chromatography and Mass Spectrometer analysis.

Superoxide Ion: Generation and Chemical Implications

Superoxide ion (O2(•-)) is of great significance as a radical species implicated in diverse chemical and biological systems. However, the chemistry knowledge of O2(•-) is rather scarce. In addition, numerous studies on O2(•-) were conducted within the latter half of the 20th century. Therefore, the current advancement in technology and instrumentation will certainly provide better insights into mechanisms and products of O2(•-) reactions and thus will result in new findings. This review emphasizes the state-of-the-art research on O2(•-) so as to enable researchers to venture into future research. It comprises the main characteristics of O2(•-) followed by generation methods. The reaction types of O2(•-) are reviewed, and its potential applications including the destruction of hazardous chemicals, synthesis of organic compounds, and many other applications are highlighted. The O2(•-) environmental chemistry is also discussed. The detection methods of O2(•-) are categorized and elaborated. Special attention is given to the feasibility of using ionic liquids as media for O2(•-), addressing the latest progress of generation and applications. The effect of electrodes on the O2(•-) electrochemical generation is reviewed. Finally, some remarks and future perspectives are concluded.

Electrochemical properties of gold and glassy carbon electrodes electrografted with an anthraquinone diazonium compound using the rotating disc electrode method

The RDE method was combined with the electrografting procedure to prepare thick AQ films on Au and glassy carbon electrodes.

Electrocatalytic activity of various types of h-BN for the oxygen reduction reaction

Enhancement of oxygen reduction reaction activity of a Au electrode by modification with various types of BN nanostructure.

Electrochemical modification of gold electrodes with azobenzene derivatives by diazonium reduction

An electrochemical study of Au electrodes electrografted with azobenzene (AB), Fast Garnet GBC (GBC) and Fast Black K (FBK) diazonium compounds is presented. Electrochemical quartz crystal microbalance, ellipsometry and atomic force microscopy investigations reveal the formation of multilayer films. The elemental composition of the aryl layers is examined by X-ray photoelectron spectroscopy. The electrochemical measurements reveal a quasi-reversible voltammogram of the Fe(CN)6 (3-/4-) redox couple on bare Au and a sigmoidal shape for the GBC- and FBK-modified Au electrodes, thus demonstrating that electron transfer is blocked due to the surface modification. The electrografted AB layer results in strongest inhibition of the Fe(CN)6 (3-/4-) response compared with other aryl layers. The same tendencies are observed for oxygen reduction; however, the blocking effect is not as strong as in the Fe(CN)6 (3-/4-) redox system. The electrochemical impedance spectroscopy measurements allowed the calculation of low charge-transfer rates to the Fe(CN)6 (3-) probe for the GBC- and FBK-modified Au electrodes in relation to bare Au. From these measurements it can be concluded that the FBK film is less compact or presents more pinholes than the electrografted GBC layer.

Construction of multilayers of bare and Pd modified gold nanoclusters and their electrocatalytic properties for oxygen reduction

Multilayers of gold nanoclusters (GNCs) coated with a thin Pd layer were constructed using GNCs modified with self-assembled monolayers (SAMs) of mercaptoundecanoic acid and a polyallylamine hydrochloride (PAH) multilayer assembly, which has been reported to act as a three-dimensional electrode. SAMs were removed from GNCs by electrochemical anodic decomposition and then a small amount of Pd was electrochemically deposited on the GNCs. The kinetics of the oxygen reduction reaction (ORR) on the Pd modified GNC/PAH multilayer assembly was studied using a rotating disk electrode, and a significant increase in the ORR rate was observed after Pd deposition. Electrocatalytic activities in alkaline and acidic solutions were compared both for the GNC multilayer electrode and Pd modified GNC electrode.