Nanoscale Electrodes by Conducting

Electrochemical characterization
was carried out using an externally connected potentiostat
equipped with a femtoammeter and a frequency response analyzer
(Modulab, Solartron Analytical), which were calibrated using
high impedance circuits comprising 0.01100 G resistors
and 110 pF capacitors. Electrochemical characterization was
carried out in potentiostatic mode; voltages are applied across
the entire cell (probeCsHSO4composite electrode), with the
probe as the working electrode and the large composite electrode
serving as the counter and reference electrode. All voltages
reported in this work are, therefore, with respect to the
large composite counter electrode, that is, an air electrode reference
which is 1.13 V relative to 2H 2e º H2 at 150 °C.
To reduce contributions of external noise, the microscope was
placed in a copper mesh Faraday cage which, like the shielding
for the electrical leads, was grounded though the potentiostat
ground. The microscope body, which was separately grounded,
was electrically isolated from the cage. Stray capacitance and
other spurious contributions were found to depend on the current
range of the potentiostat, and therefore, open circuit corrections
were obtained by withdrawing the probe from the sample
and taking impedance measurements at each current range.
Point-wise open circuit corrections were applied to all impedance
spectra presented; a representative open circuit correction
is shown in Figure 10. Short circuit measurements, obtained by
contacting the conductive probe to a piece of gold foil, displayed
the behavior of a pure resistor with a resistance on the order
of 5 k, negligible relative to the high impedances of the
nanoprobe setup employed in this work. 电化学综合测试系统