The redox activity (Li‐ion intercalation/deintercalation) of a series of individual LiMn2O4 particles of known geometry and (nano)structure, within an array, is determined using a correlative electrochemical microscopy strategy. Cyclic voltammetry (current–voltage curve, I–E) and galvanostatic charge/discharge (voltage–time curve, E–t) are applied at the single particle level, using scanning electrochemical cell microscopy (SECCM), together with co‐location scanning electron microscopy that enables the corresponding particle size, morphology, crystallinity, and other factors to be visualized. This study identifies a wide spectrum of activity of nominally similar particles and highlights how subtle changes in particle form can greatly impact electrochemical properties. SECCM is well‐suited for assessing single particles and constitutes a combinatorial method that will enable the rational design and optimization of battery electrode materials.

Layered transition-metal dichalcogenides (TMDs), such as molybdenum disulfide (MoS2) and tungsten disulfide (WS2), have attracted considerable interest as alternatives to platinum in hydrogen evolution reaction (HER) electrocatalysis. It is generally accepted that the edge planes of 2H phase MS2 (where M = Mo or W) are catalytically active, while the basal planes are said to be “catalytically inert”, which has inspired the rational design/synthesis of defect-rich nanomaterials with an abundance of exposed edge sites. The intrinsic electrochemical properties of pristine MoS2/WS2 crystals have been largely overlooked in this material-driven approach. Herein, nanometer-resolved measurements using scanning electrochemical cell microscopy (SECCM) reveal electrochemical activity at the basal plane, including spatial variations attributed to the localized folding of the surface (e.g., mechanical strain) or variations in electronic structure (e.g., defect density) throughout the crystal. Such effects are particularly evident in synthetic WS2 compared to the natural crystal of MoS2. Catalytic activity for the HER is greatly enhanced at macroscopic surface defects on both materials, measured directly where the active edge plane is exposed (e.g., crevices, holes, cracks, etc.) with single-layer sensitivity. Aging the crystals under ambient conditions (i.e., exposed to the ambient atmosphere for 30 days) substantially decreases the HER activities of MoS2 and WS2, attributable to the presence of adventitious adsorbates or surface oxidation, which particularly affects at the active edge plane. Overall, this work presents previously unseen electrochemical phenomena at TMD electrodes, highlighting how subtle changes in sample source, structure, and history can alter the catalytic activity drastically and emphasizing the care that must be taken when interpreting conventional macroscopic electrochemical data. This study further demonstrates the advantage of probe-based electrochemical mapping for establishing structure–function relationships in electromaterials science.

The metal support of hexagonal boron nitride nanosheets has a significant effect on the electrocatalytic hydrogen evolution reaction, as visualized by scanning electrochemical cell microscopy.

Thin-film electrodes, produced by coating a conductive support with a thin layer (nanometer to micrometer) of active material, retain the unique properties of nanomaterials (e.g., activity, surface area, conductivity, etc.) while being economically scalable, making them highly desirable as electrocatalysts. Despite the ever-increasing methods of thin-film deposition (e.g., wet chemical synthesis, electrodeposition, chemical vapor deposition, etc.), there is insufficient understanding on the nanoscale electrochemical activity of these materials in relation to structure/composition, particularly for those that lack long-range order (i.e., amorphous thin-film materials). In this work, scanning electrochemical cell microscopy (SECCM) is deployed in tandem with complementary, colocated compositional/structural analysis to understand the microscopic factors governing the electrochemical activity of amorphous molybdenum sulfide (a-MoS x ) thin films, a promising class of hydrogen evolution reaction (HER) catalyst. The a-MoS x thin films, produced under ambient conditions by electrodeposition, possess spatially heterogeneous electrocatalytic activity on the tens-of-micrometer scale, which is not attributable to microscopic variations in elemental composition or chemical structure (i.e., Mo and/or S bonding environments), shown through colocated, local energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) analysis. A new SECCM protocol is implemented to directly correlate electrochemical activity to the electrochemical surface area (ECSA) in a single measurement, revealing that the spatially heterogeneous HER response of a-MoS x is predominantly attributable to variations in the nanoscale porosity of the thin film, with surface roughness ruled out as a major contributing factor by complementary atomic force microscopy (AFM). As microscopic composition, structure, and porosity (ECSA) are all critical factors dictating the functional properties of nanostructured materials in electrocatalysis and beyond (e.g., battery materials, electrochemical sensors, etc.), this work further cements SECCM as a premier tool for structure−function studies in (electro)materials science.

Sandwich-like nitrogen-doped porous carbon/graphene nanoflakes (NPCFs) are prepared via a two-step approach, firstly by using in situ polymerization of pyrrole (Py) on the surface of graphene oxide (GO) and then by KOH activation under an Ar atmosphere. As the shape-directing agent and conductive matrix, graphene sheets play an important role in enhancing NPCFs' electrochemical performance. The NPCFs exhibit high specific surface area (2502 m(2) g(-1)), short ion diffusion path (ca. 30 nm), high conductivity (72 S m(-1)) and a considerable nitrogen level (6.3 wt%). These intriguing features render NPCFs a promising electrode material for electrochemical supercapacitors, which displays high specific capacitance (341 F g(-1)), excellent rate capability (over 71% retention ratio at 50 A g(-1)) and outstanding cycling stability (almost no capacitance loss after 2000 cycles) in a 30 wt% KOH aqueous electrolyte. Besides, the assembled symmetrical supercapacitor delivers a high gravimetric energy density of 11.3 Wh kg(-1) in an aqueous electrolyte and 66.4 Wh kg(-1) in an organic electrolyte.

The redoxactivity (Li-ion intercalation/deintercalation) of as eries of individual LiMn 2 O 4 particles of known geometry and (nano)structure,w ithin an array, is determined using acorrelative electrochemical microscopystrategy.Cyclic voltammetry (current-voltage curve,I -E) and galvanostatic charge/discharge (voltage-time curve,E -t) are applied at the single particle level, using scanning electrochemical cell microscopy( SECCM), together with co-location scanning electron microscopyt hat enables the corresponding particle size, morphology,c rystallinity,a nd other factors to be visualized. This study identifies aw ide spectrum of activity of nominally similar particles and highlights hows ubtle changes in particle form can greatly impact electrochemical properties. SECCM is well-suited for assessing single particles and constitutes acombinatorial method that will enable the rational design and optimization of battery electrode materials.

A mixed solvothermal method for the preparation of h-In2O3 porous spheres and their application in degradation of RhB have been discussed.

Scanning electrochemical cell microscopy (SECCM) facilitates single particle measurements of battery materials using voltammetry at fast scan rates (1 V s −1 ), providing detailed insight into intrinsic particle kinetics, otherwise obscured by matrix effects. Here, we elucidate the electrochemistry of lithium manganese oxide (LiMn 2 O 4 ) particles, using a series of SECCM probes of graded size to determine the evolution of electrochemical characteristics from the single particle to ensemble level. Nanometer scale control over the SECCM meniscus cell position and height further allows the study of variable particle/substrate electrolyte wetting, including comparison of fully wetted particles (where contact is also made with the underlying glassy carbon substrate electrode) vs partly wetted particles. We find ensembles of LiMn 2 O 4 particles show voltammograms with much larger peak separations than those of single particles. In addition, if the SECCM meniscus is brought into contact with the substrate electrode, such that the particle−support contact changes from dry to wet, a further dramatic increase in peak separation is observed. Finite element method modeling of the system reveals the importance of finite electronic conductivity of the particles, contact resistance, surface kinetics, particle size, and contact area with the electrode surface in determining the voltammetric waveshape at fast scan rates, while the responses are relatively insensitive to Li + diffusion coefficients over a range of typical values. The simulation results explain the variability in voltammetric responses seen at the single particle level and reveal some of the key factors responsible for the evolution of the response, from ensemble, contact, and wetting perspectives. The variables and considerations explored herein are applicable to any single entity (nanoscale) electrochemical study involving low conductivity materials and should serve as a useful guide for further investigations of this type. Overall, this study highlights the potential of multiscale measurements, where wetting, electronic contact, and ionic contact can be varied independently, to inform the design of practical composite electrodes.