Photoelectrocatalysis

Abstract

Photoelectrochemistry is one of the oldest branches of electrochemistry. The development of this field can be divided into three periods. The first period started with Edmond Becquerel’s observation in 1859 of the flow of current at any illuminated silver electrode immersed in chloride solution.⁽¹⁾ The next period began in 1955, with the work of Brattain and Garrett on electrochemical photopotential.⁽²⁾ In that period several experimental and theoretical papers were published. Dewald was the first to study the electrochemical behavior of wide-band-gap semiconductors,⁽³⁾ and Green formulated the first i = i(E) dependency for photoelectrodes.⁽⁴⁾ Gerischer published several papers on the thermodynamics, chemical stability, and behavior of different redox systems at the semiconductor/solution interface.^(5,6) Myamlin and Pleskov gave the first systematic description of the electrochemistry of semiconducting materials.Memming published work on the capacitance of semiconductor electrodes.⁽⁸⁾ In 1960 Williams pointed out that semiconductor electrodes can be used in practical devices.⁽⁹⁾ This period in the history of photoelectrochemistry ended at the turning point in the sixties and seventies, when Fujishima and Honda demonstrated the possibility of self-driven water splitting in photoelectrochemical cells.⁽¹⁰⁾ The possibility of cheap production of hydrogen fuel greatly increased interest in the field of photoelectrochemistry. In the last decade further new applications of photoelectrochemistry have been developed, for example, reduction of CO₂,⁽¹¹⁾ oxidation of H₂S,⁽¹²⁾ and redox reaction of HCOOH.^(13–17) In the middle of the eighties, a theoretical interpretation of the observation of quantum yields exceeding unity^(18–21) was proposed.^(21,22) In the next section of this chapter, results from the investigation of the dependence of the hydrogen evolution reaction (HER) on the state of the semiconductor surface will be discussed. The model explaining the dependence of the rate of the HER on surface properties, that is, a model of photoelectrocatalysis, will be given. In the last part of this chapter, results on photoelectroreduction of formic acid will be presented.