Nanoscale electrochemical movies and synchronous topographical mapping of electrocatalytic materials. (12th July 2018)

• Record Type: Journal Article
• Authors: Bentley, Cameron L.; Unwin, Patrick R.
• Is Part Of: Faraday discussions. Volume 210(2018)
• Page Start: 365
• Page End: 379
• Publication Date: 2018-07-12
• Subjects: Chemistry -- Periodicals; Metallurgy -- Periodicals; Electrochemistry -- Periodicals; 540
• DOI: 10.1039/c8fd00028j
• Languages: English
• ISSNs: 1359-6640

Abstract

Abstract : Nanopipette imaging probes ( ca. 30 nm) are used to map the activity/topography of nanostructured electrocatalysts directly, revealing active sites unambiguously. Abstract : Techniques in the scanning electrochemical probe microscopy (SEPM) family have shown great promise for resolving nanoscale structure–function ( e.g., catalytic activity) at complex (electro)chemical interfaces, which is a long-term aspiration in (electro)materials science. In this work, we explore how a simple meniscus imaging probe, based on an easily-fabricated, single-channeled nanopipette (inner diameter ≈ 30 nm) can be deployed in the scanning electrochemical cell microscopy (SECCM) platform as a fast, versatile and robust method for the direct, synchronous electrochemical/topographical imaging of electrocatalytic materials at the nanoscale. Topographical and voltammetric data are acquired synchronously at a spatial resolution of 50 nm to construct maps that resolve particular surface features on the sub-10 nm scale and create electrochemical activity movies composed of hundreds of potential-resolved images on the minutes timescale. Using the hydrogen evolution reaction (HER) at molybdenite (MoS2 ) as an exemplar system, the experimental parameters critical to achieving a robust scanning protocol ( e.g., approach voltage, reference potential calibration) with high resolution ( e.g., hopping distance) and optimal scan times ( e.g., voltammetric scan rate, approach rate etc. ) are considered and discussed. Furthermore, sub-nanoentity reactivity mapping is demonstrated with glassy carbon (GC) supported single-crystalline {111}-oriented two-dimensional Au nanocrystals (AuNCs), which exhibit uniform catalytic activity at the single-entity and sub-single entity level. The approach outlined herein signposts a future in (electro)materials science in which the activity of electroactive nanomaterials can be viewed directly and related to structure through electrochemical movies, revealing active sites unambiguously.