posted on 2024-02-23, 13:08authored byJoshua J. Tully, Daniel Houghton, Ben G. Breeze, Timothy P. Mollart, Julie V. Macpherson
Electrochemical advanced
oxidation (EAO) systems are of significant
interest due to their ability to treat a wide range of organic contaminants
in water. Boron doped diamond (BDD) electrodes have found considerable
use in EAO. Despite their popularity, no laboratory scale method exists
to quantify anodic corrosion of BDD electrodes under EAO conditions;
all are qualitative using techniques such as scanning electron microscopy,
electrochemistry, and spectroscopy. In this work, we present a new
method which can be used to quantify average corrosion rates as a
function of solution composition, current density, and BDD material
properties over relatively short time periods. The method uses white
light interferometry (WLI), in conjunction with BDD electrodes integrated
into a 3D-printed flow cell, to measure three-dimensional changes
in the surface structure due to corrosion over a 72 h period. It is
equally applicable to both thin film and thicker, freestanding BDD.
A further advantage of WLI is that it lends itself to large area measurements;
data are collected herein for 1 cm diameter disk electrodes. Using
WLI, corrosion rates as low as 1 nm h–1 can be measured.
This enables unequivocal demonstration that organics in the EAO solution
are not a prerequisite for BDD anodic corrosion. However, they do
increase the corrosion rates. In particular, we quantify that addition
of 1 M acetic acid to 0.5 M potassium sulfate results in the average
corrosion rate increasing ∼60 times. In the same solution,
microcrystalline thin film BDD is also found to corrode ∼twice
as fast compared to freestanding polished BDD, attributed to the presence
of increased sp2 carbon content. This methodology also
represents an important step forward in the prediction of BDD electrode
lifetimes for a wide range of EAO applications.