A new AC-SECM mode: On the way to high-resolution local impedance measurements in SECM

Scanning electrochemical microscopy (SECM) is frequently employed to detect local chemical activity of inhomogeneous samples. Here, a modified AC-SECM mode is proposed for detecting perturbations of concentration gradients of a redox couple and electric fields imposed by the local electrochemical activity of the sample while simultaneously recording the overall impedance of the sample. The method is based on an alternating current-perturbation of the sample while recording the local alternate potential of the positioned SECM tip. The low frequency part is predominantly determined by the spatial changes in the electrochemical activity of the sample. The proposed method is intrinsically not limited by the tip size and is hence able to substantially increase the resolution of local impedance measurements.

► AC-SECM mode for acquisition of global and local impedance spectra at high spatial resolution.
► (Electro-)chemical activity deconvolution of heterogeneous samples.
► Measurement of concentration gradients of electro-active species in solution.