In the past 12-15 years an essentially new trend in electrochemistry has sprung up around the problem of solar energy conversion. Strictly speaking, this is not a purely electrochemical but an interdisciplinary field involving the fields of cataly- sis, corrosion, chemistry of disperse systems, and others. Nevertheless, electro- chemistry, to be more exact, photoelectrochemistry of semiconductors, provides a theoretical basis for new methods of converting light energy into electrical or chemical energy, which, we hope, shall find practical application in the not so dis- tant future. In the...