The New Era

This excellent group from our network have submitted an invited review to Analytical Chemistry on The New Era of High Throughput Nanoelectrochemistry.

This is an exceptional piece of work. Many congratulations to the team of authors!

The review seeks to showcase the considerable developments in key aspects of nano-electrochemistry born out of recent advances in robust nanoscale electrochemical devices and imaging techniques. Nanoscale imaging, in particular, now encompasses the wide variety of subjects covered by electrochemistry, from molecules to materials, from sensors to energy storage or conversion, and the intersection of the subject with the life sciences. Imaging electrochemical processes at the nanometre scale or detecting individual nano-objects (even molecules) in an electrochemical situation is becoming much more routine. The challenge, now and in the future, is to increase the throughput of knowledge by the development of strategies to both increase the volume and proportion of relevant data from an experiment (avoiding redundancy) and for the analysis of larger datasets. To this end, this article explores efforts made in high-throughput electrochemical analysis and imaging in the past few years.

Nanoscale electrochemical imaging (i.e., nanoscale electrochemical flux visualization and nanoscale voltammetric measurement) is most readily achieved through nanopipette-based probes, i.e., imaging by SICM and SECCM. SECCM is now used by increasing numbers of research groups in a plethora of systems impacting all fields of electrochemistry and materials. In its present form, and with further developments, including intelligent scan routines and integration with complementary (in situ) microscopy and spectroscopy techniques, SECCM is expected to open up fascinating understanding of energy storage (batteries, supercapacitors, inter alia), conversion (electrocatalysis), electrosynthesis and corrosion at the nanoscale. The application of SECCM to these problems is attractive because these processes are intricately related in real-world nanostructured materials.

Most efforts with SICM are in relation to biological entities, but in the past few years multifunctional aspects of the technique have been developed, as evident from increasing number of strategies for surface charge mapping with SICM, the use of the technique for local delivery and its integration with complementary microscopy techniques. These developments have been driven by efforts to model and understand the SICM response, particularly with regard to nanoscale mass transport. Like SECCM, this foundation is providing opportunities for progressive use of the technique to electrochemical materials related to energy storage or conversion and to corrosion.

Nanopores currently offer sensing of individual molecules or nano-objects at high frequency with high chemical selectivity (chemical throughput). Here the authors envision the increasing translation of nanopore developments to the SICM to enable high-throughput imaging of interfaces at high spatial and temporal resolution with high chemical sensitivity. They describe the enhanced information from nanopores through the use of array devices, and more detailed analysis of nanopore signals, as well as multifunctionality from the incorporation of additional electrochemical and optical detection strategies.

Optical microscopy strategies offer a fast, simple and cost effective way to monitor operando a wealth of electrochemical processes with nanoscale resolution, drawing on the concepts of super-localisation. While liquid-cell TEM offers higher resolution for in-situ and in-operando visualisation, there are some compromises on cell design (and mass transport), limitations on integrating the technique with complementary methods, and issues around the effect of the electron dose on the solvent and processes studied. The expectation is for optical methods to become an important option for the main body of electrochemists, especially if seeking quick initial insights.

The ultimate single molecule imaging limit is common for fluorescent probes, but it is now at hand with label-free imaging based on promising developments in interferometric scattering microscopy. Recent advances have shifted the technique from model plasmonic systems to more complex situations, including real-battery electrode materials, or to inspect further chemical complexity, such as competing chemical reactions. Furthermore, the wide field of view enables monitoring of thousands of nano-entities simultaneously, not just to resolve the behaviour of single entities, but also to address the question of inter-entity communications.

The development of holistic views of nanoscale electrochemistry will increasingly make use of correlative multi-microscopy approaches. In this article the authors have illustrated this aspect of nano-electrochemistry with recent examples that show how the level of structural, chemical and functional (electrochemical) information on a given system is increased massively. Storing, handling, analysing, and interpreting these data will require a shift in the field towards data science and artificial intelligence, through machine learning. The next generation of nanoscale electrochemistry and electrochemical imaging approaches will draw on automatised multi-image cross-correlation and automatised imaging tools, which will increase throughput and accelerate the discovery and rational development of electrochemical technologies so urgently needed.