Assessments of Surface Coverage after Nanomaterials are Drop Cast onto Electrodes for Electroanalytical Applications

Abstract

The drop‐casting method for the suspension of nanomaterials on conducting surfaces is a commonly used procedure for evaluating the electrochemical properties of the drop‐cast materials. In this study, we pinpoint a key limitation of the method, which may lead to misinterpretation of the obtained data, especially when evaluating heterogeneous electron‐transfer rates. The electrochemical responses recorded at 1 mm‐diameter copper electrodes modified with porous layers of drop‐cast multiwalled carbon nanotubes (MWCNTs) in 0.1 M Na2SO4 aqueous solutions were examined. Standard amounts of the MWCNTs that are typically used for the drop‐casting procedure (1 mg MWCNT in 1 mL of dimethylformamide) were deposited drop wise on the surface of the copper electrodes. Layers of MWCNTs were progressively built up on the electrode surface by varying the number of drops from 0 to 10. The ability of the MWCNTs to cover and prevent diffusion to the base copper electrode was assessed by performing oxidative cyclic (CV) and linear‐sweep voltammetry (LSV) experiments in the presence of aggressive SO42− supporting electrolyte, where a large oxidative current indicated the occurrence of corroding copper metal. It was demonstrated that a total of 10 drops of the coating solution (equivalent to 640 μg cm−2 of MWCNTs per unit area) was still insufficient in providing complete coverage over the underlying electrode surface (as a corrosion current was still observed), even though considerably lower CNT loadings have been applied in many literature reports. The electrochemical results indicate that, for experiments that utilize the drop‐casting procedure to modify electrode surfaces, it cannot be assumed that the base electrode, nor the pore structure of the coating material, does not significantly contribute to the overall observed voltammetric response.

Intrinsic electrochemical performance and precise control of surface porosity of graphene-modified electrodes using the drop-casting technique

“…Particularly in the case of nanomaterials such as carbon nanotubes and graphenes, porosity can result in possible occurrences of thin-layer diffusion and/or adsorption effects [1,10,11,14,[20][21][22] due to internal pore structures and the concomitant surface area increase [23]. However, there also remains uncertainty over the general extent to which porosity (as an extrinsic property) can influence experimental data, and which may consequently result in erroneous interpretations of apparent enhancements arising from intrinsic material properties.…”

“…Amongst its various interesting properties, those most essential to applications in electrochemistry are its high electrical conductivity [7,8] and high density of electronic states (DOS) at the edges [1,9], but extends to include a perceived "electrocatalytic effect" that is at best loosely described by lowered overpotentials and increased faradaic currents [1,10,11]. Studies on nanomaterial electrochemistry also require some form of prior electrode preparation, commonly achieved by the drop-casting [5,6,[11][12][13][14], abrasive immobilisation [15][16][17], or electrochemical deposition techniques [10,18,19]. Of these, the drop-casting (or dropcoating) technique is highly favoured by many due to its simplicity and ease of preparation.…”

Electrochemistry of Layered Graphitic Carbon Nitride Synthesised from Various Precursors: Searching for Catalytic Effects

“…It was apparent that modification with CN‐UA and CN‐UN, however, resulted in significantly enhanced oxidation peak intensities, indicating the enhanced sensitivities of these two electrode materials compared to the unmodified electrode surface. Such variation in signal intensities among the different g‐C 3 N 4 materials can be attributed to the difference in material porosities, as a slight increment in porosity can significantly enhance the voltammetric signal intensity of a material …”

“…Such variation in signal intensitiesa mong the different g-C 3 N 4 materials can be attributed to the difference in materialp orosities, as as light incrementi np orosity can significantly enhancet he voltammetric signal intensity of am aterial. [36] 2.6. Hydrogen Evolution Reaction…”

Customized Bio‐functionalization of Nanocomposite Carbon Paste Electrodes for Electrochemical Sensing: A Mini Review

“…[86], where CNTs were dispersed in a suitable solvent and an aliquot was then dropped onto the electrode surface to evaporate. To date, extensively used surfaces for casting are glassy carbon, gold and graphite electrodes, but the surface of CPEs is not commonly used for this kind of modification , . These hybrid‐nanomaterials are typically used in the form of films cast from a suspension onto bare electrode surfaces, which results in a higher surface area since the (bio)modifier covers the entire surface of the electrode and therefore, it is completely exposed to analyte solution.…”