Recent Publications Feed (ADMIN)

Many applications in modern electrochemistry, notably electrosynthesis and energy storage/conversion take advantage of the “tunable” physicochemical properties (e.g., proton availability and/or electrochemical stability) of non-aqueous (e.g., aprotic) electrolyte media. This work develops general guidelines pertaining to the use of scanning electrochemical cell microscopy (SECCM) in aprotic solvent electrolyte media to address contemporary structure−electrochemical activity problems. Using the simple outer-sphere Fc0/+ process (Fc = ferrocene) as a model system, high boiling point (low vapor pressure) solvents give rise to highly robust and reproducible electrochemistry, whereas volatile (low boiling point) solvents need to be mixed with suitable low melting point supporting electrolytes (e.g., ionic liquids) or high boiling point solvents to avoid complications associated with salt precipitation/crystallization on the scanning (minutes to hours) timescale. When applied to perform microfabrication — specifically the electrosynthesis of the conductive polymer, polypyrrole — the optimized SECCM set up produces highly reproducible arrays of synthesized (electrodeposited) material on a commensurate scale to the employed pipet probe. Applying SECCM to map electrocatalytic activity — specifically the electro-oxidation of iodide at polycrystalline platinum — reveals unique (i.e., structure-dependent) patterns of surface activity, with grains of specific crystallographic orientation, grain boundaries and areas of high local surface misorientation identified as potential electrocatalytic “hot spots”. The work herein further cements SECCM as a premier technique for structure−function−activity studies in (electro)materials science and will open up exciting new possibilities through the use of aprotic solvents for rational analysis/design in electrosynthesis, microfabrication, electrochemical energy storage/conversion and beyond.

The presence of sp2 bonded carbon on a diamond or doped diamond surface, as a result of growth or processing, can affect material properties negatively, hence removal processes must be developed. Using boron doped diamond (BDD) we investigate the effectiveness of different removal methods via electrochemistry and transmission electron microscopy. We focus on two BDD surfaces, one processed by ns laser micromachining and the second which contains sp2 bonded carbon as a result of chemical vapour deposition (CVD) growth. After micromachining a layer of ordered graphite sits on the BDD surface, topped by fissured amorphous carbon (total thickness ∼ μm). Oxidative acid treatment at elevated temperature cannot remove all the sp2 bonded carbon and much smaller clusters of perpendicularly-orientated graphite (tens of nm in diameter), capped with a thinner layer of amorphous carbon – that we term “denatured graphite” – remain. In contrast, thermal oxidation in air at 600 °C is capable of all cluster removal, and can also be used to remove sp2 bonded carbon from as-grown CVD BDD. Such understanding is important to any application where sp2 bonded surface carbon resulting from CVD growth or laser processing is detrimental for the intended application, e.g. in diamond quantum technology, photonics and electrochemistry.

Scanning electrochemical cell microscopy (SECCM) is a robust and versatile scanning electrochemical probe microscopy technique that allows direct correlation of structure-activity at the nanoscale. SECCM utilizes a mobile droplet cell to investigate and visualize electrochemical activity at interfaces with high spatio-temporal resolution, while also providing topographical information. This article highlights diverse contemporary challenges in the field of single entity electrochemistry (SEE) tackled by the increasing uptake of SECCM globally. Various applications of SECCM in SEE are featured herein, including electrocatalysis, electrodeposition, corrosion science and materials science, with electrode materials spanning particles, polymers, 2D materials and complex polycrystalline substrates. The use of SECCM for patterning structures is also highlighted.