Papers by Author: Jia Jia Wu

Abstract: Different from the corrosion under anaerobic conditions, oxygen (O₂) takes part in the cathodic reaction under aerobic conditions. Sulfate-reducing bacteria (SRB) have been regarded for many years as strictly anaerobic bacteria, but recently, they are found to be able to survive in the presence of O₂, and how they affect the oxygen reduction reaction (ORR) has not been clear. In this study, the role of sulfide, a key inorganic metabolite of SRB, in ORR has been investigated on Q235 carbon steel electrode with cyclic voltammetry and electrochemical impedance spectroscopy. Three cathodic processes are recorded on cyclic voltammograms in O₂-saturated 3.5% NaCl solution: ORR, iron oxides reduction and hydrogen evolution. The peak current of ORR decreases with the introduction of sulfide, and finally vanishes when the sulfide concentration is more than 0.5 mM. EIS reveals that sulfide leads to the disappearance of the feature of semi-infinite diffusion of ORR and the fitting results demonstrate that charge transfer resistance increases with increasing sulfide concentration. Therefore sulfide hinders the cathodic reduction of O₂ on Q235 carbon steel in 3.5% NaCl solution.

Abstract: Reduced graphene sheets (RGSs) were prepared via hydrazine reduction of exfoliated graphite oxide and their morphology was characterized by atomic force microscopy. The electrocatalytic reduction of oxygen (O₂) with RGSs was studied by cyclic and rotating risk electrode voltammetry using RGSs-modified glassy carbon electrodes in alkaline media. The results show that this modification with RGSs makes the peak potential shift in the positive direction and increases the peak current. The kinetics study shows that the numbers of electrons transferred for the oxygen reduction reaction are ca. 3 at potentials of the first reduction wave, indicating the peroxide produced can transfer into OH^–.