Laser Applications in Photoelectrochemistry

Abstract

Photoemission Studies. The UV-visible irradiation of an electrode/solution interface can stimulate any of several interesting electrode processes. If the solution does not absorb and the electrode is a metallic conductor, photoemission of electrons may occur, with the formation of solvated electrons and initiation of reactions with available scavengers. If the solution absorbs the radiation and photolysis occurs, electroactive photolytic intermediates and products may be detected at an indicator electrode by their electrolysis currents under potentiostatic conditions. If the electrode is a semiconductor and absorbs radiation sufficient to promote electrons through the band gap, oxidation or reduction process may be induced which would not occur in the absence of radiation.If a dye absorbed on a semiconductor electrode is excited by the irradiation, the excited state may undergo an oxidative or reductive electron transfer step which would not occur with the ground state species.These are examples of some of the more interesting radiation-induced electrode processes which have been studied. Much of the interest has been stimulated recently by the prospects for direct solar-to-electrical energy or solar-to-chemical energy conversion which might be possible with photoelectrochemical ce lis.(1-3) The work reported here was designed to demonstrate the utility of laser sources for these photoelectrochemical studies; we have focused our attention on those phenomena uniquely related to the characteristics of laser irradiation.In particular, we report here the results of our studies of laser-induced photoemission processes and laser -induced photolysis. The former study was undertaken to illustrate the efforts of wavelength, source power, and intensity on photoemission-related process; whereas the latter study was designed to illustrate the capabilities for photoelectrochemical quantum yield measurements on transient photolytic species made possible with a laser source.

Laser‐Induced Photoelectrochemistry: Time‐Resolved Coulostatic‐Flash Studies of Photooxidation at n ‐ TiO2 Electrodes

“…Instrumentation.--The basic ingredients of the photoelectrochemical instrumentation have been described previously (10)(11)(12)(13). A Princeton Applied Research Corporation (PAR) Model 174A polarograph was used for controlled-potentiaI flash experiments as weI1 as for cyclic voltammetry and voltage scans with CW irradiation.…”

“…Pulse photocurrent measurements were made directly from the PAR 174A polarograph as described previously (10)(11)(12)(13).…”

A laser-induced transient photovoltaic effect using blocked electrodes

“…Photovoltaic phenomena are hardly new,2 but the introduction of the laser to these experiments allows us to reexamine these phenomena in a radically new light. 3,4 We see the following advantages in using a laser to induce a photochemical perturbation in a solution. First, the perturbation is induced in a very short time-on the order of 6-10 ns-with a nitrogen-pumped dye laser.…”