Chemistry Reference
In-Depth Information
The process involved in the second step may generate intermediates to inject electrons
into the conduction band, thus accounting for the electrochemical component of the
reaction. Depending on whether it is anodically polarized or there are oxidizing species
in the solution, the contribution from the intermediates in the chemical and electro-
chemical paths varies.
541
Figure 5.66 shows the possible reaction processes, proposed
by Allongue
et al
.,
22
for the dissolution of silicon at OCP. In the first path, one mol-
ecule is generated in the first step (I) by hydrolysis of one Si-H bond. The second
is produced by the decomposition of the primary product in solution (step
IV). Alternatively, both SiH bonds may first be hydrolyzed before the Si-Si bonds are
broken. In this case, the two molecules are generated in the heterogeneous reaction
on the surface. In the second path, the Si-Si back bonds are attacked first by
leading to the detachment of the silicon atom (step V) which then further reacts with
water to form and two hydrogen molecules.
The electrochemical component of the reaction process was considered by
Allongue
et al
.
22
to be due to the electron injection associated with the hydrogen
replacement step by
Figure 5.67 illustrates the reaction steps of the electrochemical path.
According to Campbell
et al
.,
679
the difference between the chemical and elec-
trochemical mechanisms is the way in which the reaction sequence is initiated. In the
