Effects of Anode Materials and Chloride Ions on Current Efficiency of Electrochemical Oxidation of Carbohydrate Compounds

Abstract

This study interrogated IrO2, RuO2, IrRuO2, Pt, and boron doped diamond for electrochemical oxidation of alginic acid and glucose. Linear sweep voltammetry estimated onset potential of oxygen evolution reaction from 1.03 to 2.60 V NHE in an inverse relation with the current efficiency of free chlorine generation in NaCl solutions, while further oxidation of free chlorine (chlorate ion generation) underestimated the current efficiency on Pt and boron doped diamond. Electrochemical oxidation experiments at 50 mA cm(-2) confirmed the free chlorine to be the primary oxidant for chemical oxygen demand degradation on the dimensionally stable anodes since the current efficiency of free chlorine generation (25-35%) was comparable with the current efficiency of chemical oxygen demand degradation. The ClO3- generation on Pt was retarded in alginic acid degradation, but effective during glucose degradation due to different reactivity with free chlorine. For boron doped diamond, direct and center dot OH mediated oxidation were significant (11% for alginic acid and 22% for glucose) and competition among organic pollutants, Cl-, and free chlorine for center dot OH determined the current efficiency of organic compounds degradation. In a saline water, IrO2 anode was the most energy-efficient (specific energy consumption for alginic acid: 48 Wh gCOD(-1)) with minimal formation of ClO3-. (C) 2019 The Electrochemical Society.