Abstract
This paper reports the adsorption of airborne and waterborne hydrocarbon contaminants on graphite and their impact on the graphite-water interfacial properties. Exposing a freshly exfoliated highly oriented pyrolytic graphite (HOPG) surface to ambient air and 1-octadecene vapor (ca. 1 ppm) caused a ca. 30% and 70% decrease in its double layer capacitance, respectively. Similarly, a 38% decrease of capacitance was observed within 1500 min after a freshly cleaved HOPG was immersed in 1 M NaCl solution; liquid phase ellipsometry data showed that a contamination layer of ca. 0.6–2 nm was formed on the HOPG surface within the same time frame. The capacitance of a contaminated sample can be partially and temporarily restored by applying a high or low potential (−1.222 V or 0.778 V vs. Ag/AgCl). Herein we report that hydrocarbon contamination on graphite is significant in both water and air.
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