Chronoamperometric Studies of Flash Photoemission at a Mercury Electrode

Abstract

Flash irradiation and high speed potentiostatic monitoring have been utilized to study the electrochemical processes associated with the photoemission of electrons from a mercury electrode into various electrolyte solutions. Conditions in which no efficient hydrated electron scavenging species was present, as well as conditions employing 10−3 M concentrations of NO2− , H3O+ , NO3− , and acetophenone, were examined. The magnitudes of the resulting flash photocurrents and their variation with electrode potential agreed qualitatively with results obtained previously using continuous radiation or coulostatic monitoring techniques. The temporal behavior of the currents showed that they were capacitive in nature, resulting from double layer recharging in response to the electron pulse caused by the extremely rapid electron emission and scavenging reactions. The charging current model appears valid for the wide variety of scavenging situations considered in this work.

Photoinduced Electrochemical Reduction of Nitrite at an Electrochemically Roughened Silver Surface

“…10 Highly promising photoassisted reduction of nitrate has been also studied at mercury electrodes immersed in suspensions of semiconductor particles. [11][12][13] The first observation of the photoelectric effect at a metalelectrolyte interface is attributed to Becquerel, who in 1839 noted an electric current between two electrodes immersed in dilute acid solution when one of the electrodes was illuminated with light. 14 Following his observation, this effect was extensively studied and finally demonstrated to result from photoemission process (reviewed in ref 15).…”

Photoelectrochemical Studies of Solvated Electron Interactions With Biological Systems

“…As has been shown previously (Baldwin and Perone, 1976), the temporal dependence exhibited in simple current-time measurements is not directly related to the time dependences of the virtually instantaneous photoemission and scavenging processes, but is determined by the electrochemical cell time-constant and the overall instrument response time. Consequently, when comparing the amplitudes of different current-time measurements quantitatively, it was not proper to compare current values measured at the same absolute elapsed time following the flash.…”

“…The flash irradiation source, optical design, electrochemical monitoring instrumentation, cell, and electrode design used in this work have been described in detail elsewhere (Kirschner and Perone. 1972;Baldwin and Perone, 1976). The flash source was a Suntron-6C xenon flash lamp (Xenon Corp., Medford.…”

“…3-6), constructed by taking the ratio of the currents observed for two different hydrated electron scavengers, were corrected for any time-constant variation for the two scavenger solu-TRlGLYClNE POTENTIAL, V vs. SCE tions; as a result, the ratio profiles always represent current values measured at the same number of cell time-constants after the end of the flash. Cell time-constants were determined as described previously (Baldwin and Perone, 1976); that is, by plotting vs time the logarithm of either the charging current following a small potential step, or the photocurrent following the flash. Such plots were linear, with the slope equal to the negative reciprocal of the cell time-constant.…”

“…Upon scavenging, the primary and secondary products may return to the electrode surface and, depending on their redox properties and on the electrode potential, participate in a further electrode reaction (either OXIDATION or REDUCTION). In any specific scavenging situation, the current-voltage profile observed at the photoemitting electrode following irradiation is the net result of all the possible redox processes described above and can be related to the specific scavenging reactions that happen to be occurring (Baldwin and Perone, 1976).…”