STRUCTURAL CHARACTERIZATION, ELECTROCHEMICAL REACTIVITY, AND RESPONSESTABILITY OF HYDROGENATED GLASSY-CARBON ELECTRODES

The physical structure, electrochemical reactivity, and response stabi lity of hydrogenated glassy carbon (HGC) electrodes were investigated using atomic force microscopy (AFM), Raman spectroscopy, X-ray photoel ectron spectroscopy (XPS), static secondary ion mass spectrometry(SIMS ), cyclic voltammetry, and chronocoulometry. The electrochemical resul ts indicate that glassy carbon surfaces, modified in a hydrogen microw ave plasma, exhibit lower background voltammetric currents, comparable electrochemical activity, enhanced S/B ratios, and improved response stability for several aqueous-based redox analytes, compared with poli shed (i.e., oxygenated) glassy carbon (GC). Also, negligible adsorptio n of anthraquinone-2,6-disulfonate (2,6-AQDS) occurs on HGC, unlike po lished GC, a surface on which AQDS strongly physisorbs at high coverag es. The hydrogenated surface contains very Little surface oxygen (O/C less than or equal to 0.03) and is hydrophobic with a contact angle of >65 degrees. Static SIMS measurements reveal a significant fraction o f the surface is composed of aliphatic hydrocarbon species (e.g. CH3, C3H3, C2H5, C3H5, etc.). Rapid electrode reaction kinetics are observe d for Fe(CN)(6)(3-/4-) and Ru(NH3)(6)(2+/3+); while slightly slower ki netics are observed for dopamine, 4-methylcatechol, and especially Fe2 +/3+. The voltammetric response for all of these analytes is extremely stable even after 3 months of exposure to the laboratory air, indicat ing the hydrogenated surface resists deactivation more so than polishe d GC. The effect of the supporting electrolyte (NaF, NaCl, NaBr, KF, K Cl, and KBr) on the k degrees for Fe(CN)(6)(3-/4-) was also studied. U nlike the case for GC, for which there is a significant electrolyte ef fect, particularly in KCl, only a weak electrolyte effect was observed for HGC. The results demonstrate that hydrogenation is a suitable mod ification method to activate and stabilize GC.