The electrochemical property of graphite depends on the specific morphology, and size, of the particle crystals. Natural graphite is classified according to its grain size. Graphite can be classified further as glassy carbon electrodes or highly ordered pyrolytic (HOPG) graphite depending on the surface chemistry1. GCEs, HOPGs, and other electrodes are commonly used in basic electrochemical applications due to their chemical stability, wide potential window, and ease modification and functionalization. The high cost and difficulty of fabrication of these electrodes limits their use in research labs.
In recent decades, several approaches were developed to enhance the performance graphite electrodes for LIB. For example, the reversible extraction/insertion of Na+ ions from/into hard-carbon has been utilized as an efficient approach to improve H2O2 yield. However, reversibility of the process is highly dependent on electrode surface chemistry. The development of new electrodes with low stoichiometry is of interest in order to facilitate the process.
Currently, there are two common forms of graphite-based electrodes for electrochemical applications: screen-printed electrodes and carbon paste electrodes (CPE). Screen-printed electrodes can only be used once, and the formula of the carbon-based dye used in their manufacture is proprietary. The electrochemical performance is also highly dependent upon the graphite rod formulation of CPEs, which is often not specified by commercial suppliers.
In order to address these issues, high-purity graphite disc electrodes (GDEs), which are used in fundamental electrochemistry experimentation, have been fabricated and characterized. GDEs were fabricated using a cost-effective method that uses readily available laboratory equipment. SEM, EDX, and XPS were used to characterize the physical properties of these electrodes. The results indicate the GDEs to have a high degree of porosity and no metallic interferences. They also show promising electrochemical performances for fundamental research. To demonstrate their practicality, the GDEs were used to immobilize peptides and enzymes and were found to be suitable for protein film electrochemistry and bioelectrocatalysis.
Dropcasting BOD on the GDE showed similar catalytic reactions. The GDEs also showed a direct heterogeneous transfer (DET), which is a reaction between bilirubin oxide and bilirubin. This reaction confirmed the potential of these electrodes for bioelectrochemistry.
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