Photoelectrochemistry and/or semiconductor electrochemistry are of active research fields and thousands of papers in these fields are published annually. They attract many research groups because their potential importance in achieving low carbon society based on renewable energy, i.e., solar energy. Research on photoelectrochemistry was very active in late 1970's and 1980's after the 1st oil crisis following the suggestion by Fujishima and Honda that solar energy may be directly converted to a chemical energy, hydrogen, by using semiconductor/aqueous electrolyte solution/metal cells,¹ although semiconductor electrochemistry was studied systematically since 1950's and many reviews and books were published by early 1970's.^2-8 ECS organized symposia on photoelectrochemistry/semiconductor electrochemistry in the annual meetings and many proceeding volumes were published.^9-14 Major target of the research changed from solar energy conversion to environmental issues and activity declined due to the lack of funding, particularly in the US. There must be reasons why photoelectrochemistry lost supports as solar energy conversion process in 1990's and it is a good time to look back what had been achieved, what were the problems, and are these problems solved.

In this talk, I will try to sum up the results achieved by 1990's and compare them with current activities.

References

1. A.Fujishima and K. Honda, Nature, 238 (1972) 37.

2. M. Green, in Modem Aspects of Electrochemistry, No. 2. Ed. by J. O’M. Bockris, Butterworths, London, 343-407 (1959).

3. J. F. Dewald. in Semiconductors. ACS Monograph, No. 140, Ed . by N. B. Hannay, Reinhold, New York, 727-752 (1959).

4. H. Gerischer. in Adv. Electrochem. Electrochem. Eng., Vol. 1, Ed . by P. Delahay, Interscience, New York, 139-232 (1961).

5. P. J. Holmes. Ed.. The Electrochemistry of Semiconductors, Academic. London, 1962.

6. V. A. Myamlin and Yu. V. Pleskov，Electrochemistry of Semiconductors. Plenum, New York. 1967.

7. H. Gerischer, in Physical Chemistry: An Advanced Treatise, Vol. IXA. Ed. by H. Eyring. Academic. New York. 1970, Chap. 5.

8. S. R. Morrison, Prog. Surf. Sci., 1(1971) 105.

9. PV 77-3 "Semiconductor Liquid-Junction Solar Cells", Ed. A. Heller.

10. PV 82-3 "Photoelectrochemistry: Fundamental Processes and Measurement Techniques", Ed. W. L. Wallace, A. J. Nojik, and S. K. Deb.

11. PV 88-14 "Photoelectrochemistry and Electrosynthesis on Semiconducting Materials", D. S. Ginley, A. Nojik, N. Armstrong, K. Honda, A. Fujishima, T. Sakata, and T. Kawai.

12. PV 93-18 Environmental Aspects of Electrochemistry and Photoelectrochemistry", M. Tomkiewicz, H. Yoneyama, R. Haynes, and Y. Hori.

13. PV 94-19 "Water Purification by Photocatalytic, Photoelectrochemical, and Electrochemical Processes", T. L. Rose, E. Rudd, O. Murphy, and B. E. Conway.

14. PV 97-20 "Photoelectrochemistry", .K. Rajeshwar, L. M. Peter, A. Fujishima, D. Meissner, and M. Tomkiewicz.