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ABSTRACT
Cyclic voltammetry (CV), one of the most useful technique to investigate the electrocatalytic behaviour, is applied to determine the stability and durability of three noble metal catalysts. The current response due to a potential sweep gives us an electrochemical spectrum of the electrode surface, with information regarding the solid-state redox transitions, active area and the electrode capacitance. The CV's graphs obtained are used to determine the number of moles that are reduced/oxidized at the electrode during the reaction; by taking into consideration the area under the curve of the voltammogram. There are several noble metal nanoparticles (e.g., Pt, Au, Pd, and Rh) supported on carbon materials that are usually used as catalyst for heterogeneous and electrochemical catalysis. The present work investigates the electrochemical behaviour, by cyclic voltammetry (CV) method of three different catalysts, namely: commercial 10% Pt/C, graphene oxide (GrO) and platinum deposed on graphene oxide (Pt/GrO). The activity and stability of prepared samples versus commercial catalyst was investigated by CV. The study compares also, the durability of the three catalytic materials after 200 cycles in the potential range from -0.35-1 V vs Ag/AgCl reference electrode.
Keywords: Voltammetry, graphene, noble catalyst, Pt/graphene oxide catalyst.
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1.INTRODUCTION
Cyclic voltammetry is the most widely used electrochemical technique to investigate the reduction and oxidation processes of molecular species. The might of cyclic voltammetry comes from its competence to rapidly ensure considerable information on the thermodynamics of redox processes and the kinetics of heterogeneous electron-transfer reactions and on coupled chemical reactions or adsorption processes.
The utility of cyclic voltammetry is highly dependent on the studied analytes. The analyte has to be redox active within the potential window to be scanned (1). If the present analyte is Fe3+(aq) in low concentration, its distribution close to the electrode surface is initially constant. The electrochemical reaction take place when an adequate voltage is applied, therefore a current start flowing due to the reaction:
... (1)
The concentration of Fe3+ close to the electrode will slowly decrease and therefore the current will also diminish in time (Wang, 2000).
In a cyclic voltammetry experiment the potential of working electrode is ramped straight versus time. After the set potential is obtained in a CV test, the potential of the...