LASER-INDUCED TRANSIENT CURRENTS ON GLASSY-CARBON ELECTRODES - DOUBLE-LAYER AND ION ADSORPTION EFFECTS

Intense laser pulses delivered to a glass carbon (GC) surface in situ result in a transient current which depends both on electrode potential and the electrolyte solution., The transient decayed with a time constant of several hundred microseconds, much longer than the laser optical or thermal transient. The linear dependence of the transient charges on potential implies that the mechanism involves perturbation and restoration of the double layer and adsorbed ions. The charge contained in the current transient was a small (<10%) fraction of the total double layer charge indicating incomplete disruption of the double layer. In addition, the magnitude of the response is higher for surf aces with higher oxide coverage. The observations are consistent with adsorption of electrolyte cations with the strength of interaction decreasing in the order H+ > Li+ > Na+ > K+ > Et4N+. The cation interaction increases with increasing surface oxidation, probably because of interactions with surface functional groups.