Borohydride oxidation electrocatalysis at individual, shape‐controlled Au nanoparticles

Abstract

Nanostructured materials are frequently employed as active components in electrochemical devices for energy conversion and storage. Unfortunately, the complexity of nanostructured materials, which can exhibit significant heterogeneities in morphology and/or composition within a macroscopic sample, makes it difficult to generate fundamental insights into their operation using traditional experimental techniques. Analytical methods that can probe the behavior of individual, discrete reactive entities, such as nanoparticles (NPs), may serve as powerful tools for the study of complex, heterogeneous systems, but remain experimentally challenging. Here, the application of probe-based electroanalytical methods is demonstrated to be a powerful, high-throughput strategy for the characterization of electrocatalytic systems. A pipet-based approach, Targeted Electrochemical Cell Microscopy (TECCM), was applied to characterize the electrocatalytic properties of individual, shape-controlled Au NPs toward the borohydride oxidation reaction (BOR), a model fuel cell reaction.Using TECCM, the BOR could be quantitatively interrogated at individual NPs in a high-throughput fashion, directly revealing significant NP-to-NP variations in reactivity and stability. BOR kinetics were found to exhibit a significant shape dependence, generally increasing in the order Triangles < Spheres ≈ Octahedra < Rods, and prominent voltammetric features were observed that could be attributed to surface deactivation/reactivation process occurring at individual NPs. Together, these results demonstrate the large degree to which catalytic behavior varies at the single NP level and the power of applying single NP analytical techniques to the study of these systems.

On-Demand Electrochemical Fabrication of Ordered Nanoparticle Arrays using Scanning Electrochemical Cell Microscopy

“…SECCM electrodeposition experiments were carried out using a home-built SECCM apparatus which has been described in detail elsewhere. − An ITO substrate served as the working electrode. SECCM probes were mounted to a 3-axis piezo system (PI Nanocube 611.3S and E-727 controller).…”

Hybrid scanning electrochemical cell microscopy-interference reflection microscopy (SECCM-IRM): tracking phase formation on surfaces in small volumes

“…Scanning electrochemical cell microscopy (SECCM) provides a powerful platform to create very well defined and consistent microscale and nanoscale-sized electrochemical cells on various substrates. 36,37 Since its inception, 38,39 SECCM, and the scanning micropipette contact method (SMCM) as an earlier variant was named, has been widely employed to investigate electrochemical processes at the nanoscale, revealing heterogeneous properties of many features of materials including 2D materials, 36,[40][41][42][43] nanotubes, 44,45 grain boundaries and crystallographic facets in electrodes and electrocatalysts, [46][47][48] single particles, [49][50][51][52][53] among a rapidly expanding range of applications. 37 For phase formation and phase change processes, the ability to confine electrochemical reactions to small volumes allows the investigation of a few or even single events.…”

Nanoscale Visualization of Electrochemical Activity at Indium Tin Oxide Electrodes

“…This scanning probe technique utilizes a mobile meniscus formed at the end of a nanopipette to confine electrochemical measurements to local regions of a substrate. By hopping or scanning the probe across a surface of interest, it is possible to track both electrochemical activity and topography synchronously, thereby allowing the unambiguous visualization of electrochemical processes. , This approach has been applied extensively to resolve activity at complex electrodes, including single carbon nanotubes, individual nanoparticles, − composite conductive polymer films, polycrystalline metal surfaces, , highly oriented pyrolytic graphite (HOPG) and graphene, two-dimensional (2D) materials, , polycrystalline boron-doped diamond, screen-printed carbon electrodes, and semiconductor electrodes, among others.…”