Injection of solution species into glassy carbon electrodes has been monitored by Phase Detection Microscopy (PDM), and by sputter profiling and surface analysis. Electrochemical treatment in strongly alkaline solutions at positive voltage conditions caused swelling of the surface at local spots and eventual disruption of the surface with the formation of pits. The number, size, and depth of the pits increased with increased voltage. X-ray Photoelectron Spectroscopy (XPS) depth profiles revealed the presence of oxygen species below the surface at depths that were dependent on electrochemical treatment. Increased positive voltage or increased treatment time gave surfaces with oxygen at greater depths below the surface. Glassy carbon, activated as described here, has been found to support a high rate oxidation of S2- to polysulfides.