la9b02043_si_001.pdf (585.37 kB)
Electrochemically Enhanced Dissolution of Silica and Alumina in Alkaline Environments
journal contribution
posted on 2019-08-27, 17:33 authored by Howard
A. Dobbs, George D. Degen, Zachariah J. Berkson, Kai Kristiansen, Alex M. Schrader, Tandré Oey, Gaurav Sant, Bradley F. Chmelka, Jacob N. IsraelachviliDissolution
of mineral surfaces at asymmetric solid–liquid–solid
interfaces in aqueous solutions occurs in technologically relevant
processes, such as chemical/mechanical polishing (CMP) for semiconductor
fabrication, formation and corrosion of structural materials, and
crystallization of materials relevant to heterogeneous catalysis or
drug delivery. In some such processes, materials at confined interfaces
exhibit dissolution rates that are orders of magnitude larger than
dissolution rates of isolated surfaces. Here, the dissolution of silica
and alumina in close proximity to a charged gold surface or mica in
alkaline solutions of pH 10–11 is shown to depend on the difference
in electrostatic potentials of the surfaces, as determined from measurements
conducted using a custom-built electrochemical pressure cell and a
surface forces apparatus (SFA). The enhanced dissolution is proposed
to result from overlap of the electrostatic double layers between
the dissimilar charged surfaces at small intersurface separation distances
(<1 Debye length). A semiquantitative model shows that overlap
of the electric double layers can change the magnitude and direction
of the electric field at the surface with the less negative potential,
which results in an increase in the rate of dissolution of that surface.
When the surface electrochemical properties were changed, the dissolution
rates of silica and alumina were increased by up to 2 orders of magnitude
over the dissolution rates of isolated compositionally similar surfaces
under otherwise identical conditions. The results provide new insights
on dissolution processes that occur at solid–liquid–solid
interfaces and yield design criteria for controlling dissolution through
electrochemical modification, with relevance to diverse technologies.