Investigations of electrochemical oxygen transfer reaction on boron-doped diamond electrodes
ABSTRACT In this paper, the electrochemical oxygen transfer reaction (EOTR) is studied on boron-doped diamond electrodes using simple C1 organic compounds (methanol and formic acid). The kinetics of both oxygen evolution (side reaction) and organics oxidation (main reaction) has been investigated using boron-doped diamond microelectrodes-array (BDD MEA). Oxygen evolution, in the high-potential region, takes place with a Tafel slope of 120 mV dec−1 and zero reaction order with respect to H+. In the presence of organics, a shift of the polarization curves to lower potentials is observed while the Tafel slopes remain close to 120 mV dec−1. A simplified model of C1 organics oxidation is proposed. Both water discharge and organics oxidation are assumed to be fast reactions. The slowest step of the studied EOTR is the anodic discharge of hydroxyl radicals to oxygen. Further in this work, electrolysis of formic acid on boron-doped diamond macroelectrode is presented. In order to achieve 100% current efficiency, electrolysis was carried out under programmed current, in which the current density was adjusted to the limiting value.
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ABSTRACT: A pulse current technique was conducted in a boron-doped diamond (BDD) anode system for electrochemical wastewater treatment. Due to the strong generation and weak absorption of hydroxyl radicals on the diamond surface, the BDD electrode possesses a powerful capability of electrochemical oxidation of organic compounds, especially in the pulse current mode. The influences of pulse current parameters such as current density, pulse duty cycle, and frequency were investigated in terms of chemical oxygen demand (COD) removal, average current efficiency, and specific energy consumption. The results demonstrated that the relatively high COD removal and low specific energy consumption were obtained simultaneously only if the current density or pulse duty cycle was adjusted to a reasonable value. Increasing the frequency slightly enhanced the COD removal and average current efficiency. A pulse-BDD anode system showed a stronger energy saving ability than a constant-BDD anode system when the electrochemical oxidation of phenol of the two systems was compared. The results prove that the pulse current technique is more cost-effective and more suitable for a BDD anode system for real wastewater treatment. A kinetic analysis was presented to explain the above results.International Journal of Minerals Metallurgy and Materials 20(1). · 0.48 Impact Factor