The sol–gel processing method was used for fabricating of CCE
according to the following procedure: The amount of 0.9 mlMTMOS
was mixed with 0.6 ml methanol. After addition of 0.6 ml HCl
0.5M as catalyst, the mixture was magnetically stirred (for about
15 min) until to achieve a clear and homogeneous solution. Then,
0.3 g graphite powder was added and the mixture was shaken for
an additional 5min. Subsequently, the homogenized mixture was
firmly packed into a Teflon tube (with 3.9mm inner diameter and
10mm length) and dried for at least 24 h at room temperature. A
copper wire was inserted through the other end to set up electric
contact. The electrode surfacewas polishedwith 1500 emery paper
and was rinsed with distilled water.