Electrochemical 3D-growth of amorphous silica gel

- A pseudo 3D-like growth of silica was investigated on stainless steel.
- Electrochemically assisted sol-gel deposition shows progressive nucleation behavior.
- Current transient are the result of H3O+ reduction at the electrode surface.
- The H3O+ availability depends on SiOH sites close to the electrode surface.
- H3O+ migrates through the porous silica gel structure along neighboring SiO sites.

The electrochemically assisted sol-gel deposition of silica (EADS) is an emerging technology, which allows the deposition of a silica layer under local basic conditions using a stable acidic solution of tetraethyl orthosilicate. In this paper, the EADS process was fully characterized by cyclic voltammetry and chronoamperometry, under different conditions; i.e. precursor concentration and applied potential. Moreover, thickness was measured at different times by ellipsometry, whereas scanning electron microscopy was used to investigate the morphology. Surprisingly we found that the potentiostatic current transient resembles that of a typical nucleation and growth galvanic deposition. This phenomenon was explained on the basis of an increased proton availability and conductivity trough the Si-OH groups of hydrated diffused sol-gel layer.

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