Photoelectrochemical effects

Semiconductor electrodes exhibit electron photoemission into the solution, like metal electrodes, but in addition they exhibit further photoelectrochemical effects due to excitation of the electrode under illumination. The first observations in this area were made toward the middle of the twentieth century. At the end of the 1940s,... 

The surprising variety of photoelectrochemical effects observed at silicon electrodes anodized in HF is solely a consequence of the semiconducting nature of the electrode, because the electrolyte is not photoactive. 

Photoelectrochemical effect involves production of a voltage and an electric current when light falls on a semiconductor electrode immersed in an electrolyte solution and connected to a counter electrode (Becquerel, 1839). Working with germanium electrodes, Brattain Garrett (1955) showed that the Becquerel effect was due to the formation of a semiconductor-electrolyte junction. The idea of using an illuminated... 

Solovev AA, Katz E, Shuvalov VA, Erokhin YE (1991) Photoelectrochemical effects for chemically modified platinum electrodes with immobilized reaction centers for Rhodobacter sphaeroides R-26. Bioelectrochem Bioenerg 26 29-41... 

In the present article, various fundamental photoelectrochemical effects are quantitatively described and discussed, with the main emphasis on the kinetics of charge transfer processes. Although in principle the same reaction mechanisms are valid for extended semiconductor electrodes and particles, different factors govern the reaction rate, as will be discussed in detail. Finally, a brief overview of various applications will be given. 

Many studies based on the observed bulk photoelectrochemical effects and on direct probing of the processes occurring at the solid surface have provided firm evidence that the sensitizing mechanism involves as a primary step electron or hole injection by the electronically excited sensitizer molecule (S ) into the semiconductor (SC). 

H. Koyama and N. Koshida, Photoelectrochemical effects of surface modification of n-type Si with porous layer, J. Electrochem. Soc. 138 254, 1991. 

Schmidt, A., and Armstrong, N.R. (1996) Photoelectrochemical effects and (photo)conductivity of n-type phthalocyanines. Mol. Cryst. Liq. Cryst., 283, 283-291. 

It was also found that systems undergoing electropolishing exhibit a significant photoelectrochemical effect. This corresponds to the region of limiting diffusion current densities and also to the maximum polishing effect. 

It was found that electropolishing occurs in systems which, under anodic dissolution, exhibit a limiting current characteristic of diffusion control, i.e., currents are dependent on flow rate of the electrolyte past the anode, as shown in Figure 24. Over a certain range of potentials at the limiting current plateau, at which maximum brilliance is obtained, oscillations of potential occur at a virtually constant current density, with an amplitude of over 0.40 V, and without appreciable damping. Also, a significant photoelectrochemical effect is found. 

Zaitsev, N., Gorehk, O., Kotov, N. et al. (1988) A photoelectrochemical effect at the polarizable interface between liquid electrolyte-solutions in protoporphyrin quinone systems. Soviet Electrochemistry, 24 (10), 1243-1247. 

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