Mechanism of Perchlorate Formation on Boron-Doped Diamond Film Anodes

摘要

This research investigated the mechanism of perchlorate (C1O_4~-) formation from chlorate (C1O_3~-) on boron-doped diamond (BDD) film anodes by use of a routing disk electrode reactor. Rates of C1O_4~- formation were determined as functions of the electrode potential (2.29-2.70 V/ standard hydrogen electrode, SHE) and temperature (10-40 ℃). At all applied potentials and a ClO_3~- concentration of 1 mM, ClO_4~- production rates were zeroth-order with respect to ClO_4~-concentration. Eiperimental and density functional theory (DFT) results indicate mat ClO_3~- oxidation proceeds via a combination of direct electron transfer and hydroxyl radical oxidation with a measured apparent activation energy of 6.9 ± 18 kJ·mol~(-1) at a potential of 2.60 V/SHE DFT simulations indicate that the ClO_4~-formation mechanism involves direct oxidation of ClO_3 at the BDD surface to form ClO_3,which becomes activationless at potentials> 0.76 V/SHE Perchloric acid is thenformed via the activationless homogeneous reaction between ClO_3 and OH in the difhuse layer next to the BDD surface. DFT simulations also indicate that die reduction of ClO_3 can occur at radical sites on the BDD surface to form ClO_3~- and ClO_2, which limits me overall rate of ClO_4~- formation.