Analytical Chemistry 77 (2005) 3479-3487

In Situ Spatial and Time-Resolved Studies of Electrochemical Reactions by Scanning Transmission X-ray Microscopy


Daniel Guay,† Jacob Stewart-Ornstein,‡ Xuerong Zhang,‡ and Adam P. Hitchcock‡

(†) Centre Energie, Materiaux et Telecommunications, Institut National de la Recherche Scientifique, Varennes, QC, Canada J3X 1S2,
(‡) Department of Chemistry and Brockhouse Institute for Materials Research, McMaster University, Hamilton, ON, Canada L8S 4M1

The first in situ measurements with scanning transmission X-ray microscopy (STXM) of an active electrochemical cell are reported. An electrochemical wet cell, consisting of an electrodeposited polyaniline thin film on a thin Au film covered by an overlayer of 1 M HCl solution sitting between two X-ray transparent silicon nitride windows, was assembled. X-ray absorption images and spatial and time-resolved spectra of this system under potential control were examined using the beamline 5.3.2 STXM at the Advanced Light Source. The chemical state of the polyaniline film was reversibly converted between reduced (leucoemeraldine) and oxidized (emeraldine chloride) states by changing the applied potential. The electrochemical changes were monitored by spatially resolved C 1s and N 1s X-ray absorption spectroscopy and chemical-state selective imaging. Comparison of differences between images at two energies at different potentials provided electrochemical contrast with a resolution better than 50 nm, thereby monitoring that component of the polyaniline film that was electrochemically active. Kinematic studies in the subsecond regime are demonstrated.

10.1021/ac048077j CCC:      © 2005 American Chemical Society