Compressed Sensing Image Reconstruction of Scanning Electrochemical Microscopy Measurements Carried Out at Ultrahigh Scan Speeds Using Continuous Line Probes.

Previous studies on scanning electrochemical microscopy (SECM) imaging with nonlocal continuous line probes (CLPs) have demonstrated the ability to increase areal imaging rates by an order of magnitude compared to SECM based on conventional ultramicroelectrode (UME) disk electrodes. Increasing the linear scan speed of the CLP during imaging presents an opportunity to increase imaging rates even further but results in a significant deterioration in image quality due to transport processes in the liquid electrolyte. Here, we show that compressed sensing (CS) postprocessing can be successfully applied to CLP-based SECM measurements to reconstruct images with minimal distortion at probe scan rates greatly exceeding the conventional SECM ″speed limit″. By systematically evaluating the image quality of images generated by adaptable postprocessing CS methods for CLP-SECM data collected at varying scan rates, this work establishes a new upper bound for CLP scan rates. While conventional SECM imaging typically uses probe scan speeds characterized by Péclet numbers (Pe) < 1, this study shows that CS postprocessing methods can allow for an accurate image reconstruction for Pe approaching 5, corresponding to an order of magnitude increase in the maximum probe scan speed. This upper limit corresponds to the onset of chaotic convective flows within the electrolyte for the probes investigated in this work, highlighting the importance of considering hydrodynamics in the design of fast-scanning probes.

Design and operation of a scanning electrochemical microscope for imaging with continuous line probes.

This article describes a home-built scanning electrochemical microscope capable of achieving high areal imaging rates through the use of continuous line probes (CLPs) and compressed sensing (CS) image reconstruction. The CLP is a nonlocal probe consisting of a band electrode, where the achievable spatial resolution is set by the thickness of the band and the achievable imaging rate is largely determined by its width. A combination of linear and rotational motors allows for CLP scanning at different angles over areas up to 25 cm2 to generate the raw signal necessary to reconstruct the desired electrochemical image using CS signal analysis algorithms. Herein, we provide detailed descriptions of CLP fabrication, microscope design, and the procedures used to carry out scanning electrochemical microscopy imaging with CLPs. In order to illustrate the basic operating procedures for the microscope, line scans and images measured in the substrate generation-probe-collection mode for flat samples containing platinum disk electrodes are presented. These exemplary measurements illustrate methods for calibrating the positioning system, positioning and cleaning the CLP, and verifying proper positioning/probe sensitivity along its length.

Membraneless electrolyzers for the simultaneous production of acid and base.

This study investigates the use of membraneless electrolyzers based on angled mesh flow-through electrodes for the simultaneous production of acid and base (lye) from aqueous brine solutions. These electrolyte-agnostic flow cells are capable of producing a wide variety of acids and bases with precisely controlled pH using a simple cell design.