Recent Publications Feed (ADMIN)

As part of the revolution in electrochemical nanoscience, there is growing interest in using electrochemistry to create nanostructured materials, and to assess properties at the nanoscale. Herein, we present a platform that combines scanning electrochemical cell microscopy with ex-situ scanning transmission electron microscopy, to allow the ready creation of an array of nanostructures coupled with atomic-scale analysis. As an illustrative example, we explore the electrodeposition of Pt at carbon-coated transmission electron microscopy (TEM) grid supports, where in a single high-throughput experiment it is shown that Pt nanoparticle (PtNP) density increases and size polydispersity decreases with increasing overpotential (i.e., driving force). Furthermore, the coexistence of a range of nanostructures − from single atoms to aggregates of crystalline PtNPs − during the early stages of electrochemical nucleation and growth supports a non-classical aggregative growth mechanism. Beyond this exemplary system, the presented correlative electrochemistry−microscopy approach is generally applicable to solve the ubiquitous structure-function problems in electrochemical science and beyond, positioning it as a powerful plat-form for the rational design of functional nanomaterials.

Conductive polymers are exceptionally promising for modular electrochemical applications including chemical sensors, bioelectronics, redox-flow batteries, and photo-electrochemical systems due to considerable synthetic tunability and ease of processing. Despite well-established structural heterogeneity in these systems, conventional macroscopic electroanalytical methods – specifically cyclic voltammetry – are typically used as the primary tool for structure-property elucidation. This work presents an alternative correlative multi-microscopy strategy; data from laboratory and synchrotron-based micro-spectroscopies, including conducting-atomic force microscopy and synchrotron nanoscale infrared spectroscopy, is combined with potentiodynamic movies of electrochemical fluxes from scanning electrochemical cell microscopy (SECCM) to reveal the relationship between electrode structure and activity. A model conductive polymer electrode system of tailored heterogeneity is investigated, consisting of phase-segregated domains of poly(3-hexylthiophene) (P3HT) surrounded by contiguous regions of insulating poly(methyl methacrylate) (PMMA), representing an ultramicroelectrode array. Isolated domains of P3HT are shown to retain bulk-like chemical and electronic structure when blended with PMMA, and possess approximately equivalent electron-transfer rate constants compared to pure P3HT electrodes. The nanoscale electrochemical data are used to model and predict multiscale electrochemical behavior, revealing that macroscopic cyclic voltammograms should be much more kinetically facile than observed experimentally. This indicates that parasitic resistances rather than redox kinetics play a dominant role in macroscopic measurements in these conducting polymer systems. SECCM further demonstrates that the ambient degradation of the P3HT electroactivity within P3HT/PMMA blends is spatially heterogeneous. This work serves as a roadmap for benchmarking the quality of conductive polymer films as electrodes, emphasizing the importance of nanoscale electrochemical measurements in understanding macroscopic properties.

Anodic Stripping Voltammetry (ASV) has the capability to detect heavy metals at sub ppb-level with portable and cheap instrumentation making it ideal for in the field (at the source) analysis, however, commercial activity is surprisingly limited. The more commonly used liquid mercury electrodes are now obsolete due to toxicity concerns, and replacements are all based around solid electrodes, which come with their own challenges. This tutorial review aims to discuss the experimental practicalities of ASV, providing a clear overview of the issues for consideration, which can serve as a guide for anyone wanting to undertake analytical ASV. Choice of electrode material (with or without subsequent modification) and solution composition (pH, electrolyte, buffer) are important parameters, as well as an understanding of pH dependent metal speciation and possible intermetallic effects. Measurements made on model solutions often differ from those made on environmental samples with the latter containing organic matter, biological and inorganic species, which themselves can adsorb metal ions. Consideration should also be given to the method of solution collection and the sample container utilised. ASV can be a powerful tool to an analytical chemist, however optimisation for the application of interest is essential, which this review aims to help guide.