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Small electrodes capable of detecting Mn dissolution and oxygen evolution are placed near operating Mn-based lithium-ion battery cathodes to track their degradation, informing on mechanism and revealing how additives might help decrease degradation. 

Hydroxyl radical and hydrogen peroxide are implicated in the poor stability of Fe–N–C catalysts. We use SECM to detect these transient species in real time to evaluate their possible sources and relationship to stability. 

Redox-active colloids (RACs) represent a novel class of energy carriers that exchange electrical energy upon contact. Understanding contact-mediated electron transfer dynamics in RACs offers insights into physical contact events in colloidal suspensions and enables quantification of electrical energy transport in nonconjugated polymers. Redox-based electron transport was directly observed in monolayers of micron-sized RACs containing ethyl-viologen side groups via fluorescence microscopy through an unexpected nonlinear electrofluorochromism that is quantitatively coupled to the redox state of the colloid. Via imaging studies, using this electrofluorochromism, the apparent charge transfer diffusion coefficientD_CTof the RAC was easily determined. The visualization of energy transport within suspensions of redox-active colloids was also demonstrated. Our work elucidates fundamental mechanisms of energy transport in colloidal systems, informs the development of next-generation redox flow batteries, and may inspire new designs of smart active soft matter including conductive polymers for applications ranging from electrochemical sensors and organic electronics to colloidal robotics. 

Conversion of glycerol to value‐added products is an attractive solution to the oversupply of this byproduct of biofuel production. The glycerol oxidation reaction (GOR) may form product mixtures derived from the scission of the three‐carbon (C3) glycerol backbone, generating one‐ (C1) or two‐carbon (C2) species. Here, the bulk and flow electrolysis (FE) of the 2,2,6,6‐tetramethyl‐1‐piperidine‐N‐oxyl (TEMPO)‐mediated GOR reaction is explored to produce a valorized C3 product, highlighting key selectivity differences between the two methods despite using the same optimized electrolyte composition. Increasing the pH of the solution dramatically increases GOR activity but presents a tradeoff with the stability of TEMPO. At an optimal pH of 10.6 in carbonate buffer in a batch reactor, the reaction proceeds with higher than 90% yield via a 10‐electron oxidation to mesoxalic acid, a C3 product. FE at much lower Reynolds number yields significantly lower selectivity toward C3, demonstrating a high sensitivity to mass transport. The work sheds light on the opportunities toward selectively producing C3 products from GOR as well as the importance of mass transfer considerations for the valorization of this key bio‐feedstock and for others involving mediated electrocatalysis. 

Developing a deeper understanding of dynamic chemical, electronic, and morphological changes at interfaces is key to solving practical issues in electrochemical energy storage systems (EESSs). To unravel this complexity, an assortment of tools with distinct capabilities and spatiotemporal resolutions have been used to creatively visualize interfacial processes as they occur. This review highlights how electrochemical scanning probe techniques (ESPTs) such as electrochemical atomic force microscopy, scanning electrochemical microscopy, scanning ion conductance microscopy, and scanning electrochemical cell microscopy are uniquely positioned to address these challenges in EESSs. We describe the operating principles of ESPTs, focusing on the inspection of interfacial structure and chemical processes involved in Li-ion batteries and beyond. We discuss current examples, performance limitations, and complementary ESPTs. Finally, we discuss prospects for imaging improvements and deep learning for automation. We foresee that ESPTs will play an enabling role in advancing EESSs as we transition to renewable energies. 

Materials that undergo ion-insertion coupled electron transfer are important for energy storage, energy conversion, and optoelectronics applications. Cyclic voltammetry is a powerful technique to understand electrochemical kinetics. However, the interpretation of the kinetic behavior of ion insertion electrodes with analytical solutions developed for ion blocking electrodes has led to confusion about their rate-limiting behavior. The purpose of this manuscript is to demonstrate that the cyclic voltammetry response of thin film electrode materials undergoing solid-solution ion insertion without significant Ohmic polarization can be explained by well-established models for finite diffusion. To do this, we utilize an experimental and simulation approach to understand the kinetics of Li⁺insertion-coupled electron transfer into a thin film material (Nb₂O₅). We demonstrate general trends for the peak current vs scan rate behavior, with the latter parameter elevated to an exponent between limiting values of 1 and 0.5, depending on the solid-state diffusion characteristics of the film (diffusion coefficient, film thickness) and the experiment timescale (scan rate). We also show that values < 0.5 are possible depending on the cathodic potential limit. Our results will be useful to fundamentally understand and guide the selection and design of intercalation materials for multiple applications.