Patternable Solvent-Processed Thermoplastic Graphite Electrodes

Abstract

Since their invention in the 1950s, composite carbon electrodes have been employed in a wide variety of applications, ranging from batteries and fuel cells to chemical sensors, because they are easy to make and pattern at millimeter scales. Despite their widespread use, traditional carbon composite electrodes have substandard electrochemistry relative to metallic and glassy carbon electrodes. As a result, there is a critical need for new composite carbon electrodes that are highly electrochemically active, have universal and easy fabrication into complex geometries, are highly conductive, and are low cost. Herein, a new solvent-based method is presented for making low-cost composite graphite electrodes containing a thermoplastic binder. The electrodes, which are termed thermoplastic electrodes (TPEs), are easy to fabricate and pattern, give excellent electrochemical performance, and have high conductivity (700 S m). The thermoplastic binder enables the electrodes to be hot embossed, molded, templated, and/or cut with a CO laser into a variety of intricate patterns. Crucially, these electrodes show a marked improvement in peak current, peak separation, and resistance to charge transfer over traditional carbon electrodes. The impact of electrode composition, surface treatment (sanding, polishing, plasma treatment), and graphite source were found to significantly impact fabrication, patterning, conductivity, and electrochemical performance. Under optimized conditions, electrodes generated responses similar to more expensive and difficult to fabricate graphene and highly oriented pyrolytic graphite electrodes. The TPE electrode system reported here provides a new approach for fabricating high performance carbon electrodes with utility in applications ranging from sensing to batteries.

Increasing Applications of Graphite Thermoplastic Electrodes with Aryl Diazonium Grafting

“…Fe(CN) 6 3−/4− exhibits inner sphere properties and requires a direct interaction with the substrate for an efficient electron transfer . TPEs have been fabricated from PMMA, COC, and PCL thermoplastics, but they have always been used in a PMMA template . Because the PMMA template restricts solvent compatibility to aqueous solutions, we began with in situ diazonium generation and modification in aqueous solution using the method introduced by Baranton and Bélanger for GC surfaces .…”

“…Two graphite types were used: 3569 graphite (“3569”, 99.9 % purity carbon, 96.9 % is ≤75 μm diameter, Asbury Graphite Mills Inc, NJ, USA) and MG‐1599 graphite (“MG”, 99.5–99.9 % purity carbon, 16 μm diameter, Great Lakes Graphite Inc., MA, USA). TPEs were fabricated as described previously . Briefly, COC (8007, TOPAS, MI, USA) was dissolved in toluene.…”

“…The binder material affects the physical and electrochemical properties of the electrode; binders that have been used in carbon composite electrodes include pasting liquids for screen printed electrodes, paraffin wax, epoxy, and various plastics . Recently, a new form of carbon composite electrodes called thermoplastic electrodes (TPEs) were reported that use a simple fabrication method to generate complex electrode geometries while maintaining high conductivity, good electron transfer kinetics, reusability, and low cost . The first report used poly(methyl methacrylate) (PMMA) as the binder, but cyclic olefin copolymer (COC) and polycaprolactone (PCL) have also been used as binders; the TPE performance changes with polymer type, carbon type, and the polymer to plastic ratio, and the graphite types used here were based upon these previous studies.…”

“…[6] Recently, a new form of carbon composite electrodes called thermoplastic electrodes (TPEs) were reported that use a simple fabrication method to generate complex electrode geometries while maintaining high conductivity, good electron transfer kinetics, reusability, and low cost. [7] The first report used poly (methyl methacrylate) (PMMA) as the binder, but cyclic olefin copolymer (COC) and polycaprolactone (PCL) [8] have also been used as binders; the TPE performance changes with polymer type, carbon type, and the polymer to plastic ratio, and the graphite types used here were based upon these previous studies. While TPEs exhibit promising results, they have not yet been used in sensing applications nor have they been used in non-aqueous solutions, limiting the available surface modification possibilities that often require processes in organic solvents.…”

Trace Analysis of Heavy Metals (Cd, Pb, Hg) Using Native and Modified 3D Printed Graphene/Poly(Lactic Acid) Composite Electrodes

“…1 and the Raman spectra in Figure d, the crystallite size is estimated to be 26 nm, which suggests significant dislocations and defects. Taken together, the information in Figure suggests that the graphene/PLA composites are comparable to other carbon‐composite electrode materials , which shows promise for its use in electroanalytical studies.…”