A monolithic photovoltaic-photoelectrochemical device for hydrogen production via water splitting

Science

Volumn 280, Issue 5362, 1998, Pages 425-427

  Khaselev, Oscar ^a   Turner, John A ^a  

^a NATIONAL RENEWABLE ENERGY LABORATORY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

HYDROGEN PRODUCTION; MONOLITHIC PHOTOVOLTAIC PHOTOELECTROCHEMICAL DEVICE; PHOTOELECTROLYSIS; WATER SPLITTING;

ELECTROLYSIS; ELECTROLYTES; ENERGY GAP; HYDROGEN; LIGHT ABSORPTION; OHMIC CONTACTS; OXIDATION; PHOTOCHEMICAL REACTIONS; SEMICONDUCTING GALLIUM COMPOUNDS; SOLID STATE DEVICES; TUNNEL JUNCTIONS; WATER;

PHOTOVOLTAIC CELLS;

WATER;

ARTICLE; DEVICE; ELECTROLYSIS; LIGHT; PRIORITY JOURNAL; SEMICONDUCTOR; SHORT CIRCUIT CURRENT;

EID: 0032540476     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.280.5362.425     Document Type: Article

References (30)

1. A. J. Bard and M. A. Fox, Acc. Chem. Res. 28, 141 (1995).
2. H. Gerischer, in Topics in Applied Physics, vol. 31, Solar Energy Conversion, B. O. Seraphin, Ed. (Springer-Verlag, Berlin, 1979), pp. 115-172.
3. The ability of a semiconductor electrode to drive the electrochemical reaction of interest is determined by its band gap (the energy separation between the valence and conduction band edges) and the position of the valence and conduction band edges relative to the vacuum level (or other reference electrode). In contrast to metal electrodes, semiconductor electrodes in contact with liquid electrolytes have fixed energies where the charge carriers enter the solution. This fixed energy is given by the energetic position of the semiconductor's valence and conduction bands at the surface (where these bands terminate at the semiconductor/electrolyte interface). The energetic position of these band edges is determined by the chemistry of the semiconductor/electrolyte interface, which is controlled by the composition of the semiconductor, the nature of the surface, and the electrolyte composition. So even though a semiconductor electrode may generate sufficient energy to effect an electrochemical reaction, the energetic position of the band edges may prevent it from doing so. For spontaneous water splitting, the oxygen and hydrogen reactions must lie between the valence and conduction band edges, and this is almost never the case.
4. G. E. Shakhnazaryan et al., Russ. J. Electrochem. 30, 610 (1994).
5. E. Aharon-Shalom and A. Heller, J. Electrochem. Soc. 129, 2865 (1982).
6. A. Heller, Science 223, 1141 (1984).
7. S. Kocha, J. Turner, A. J. Nozik, J. Electroanal. Chem. 367, 27 (1991).
8. S. Kocha and J. A.Turner, J. Electrochem. Soc. 142, 2625 (1995).
9. H. Yoneyama, H. Sakamoto, H. Tumura, Electrochem. Acta 20, 341 (1975).
10. A. J. Nozik, Appl. Phys. Lett. 29, 150 (1976).
11. R. C. Kainthla, B. Zelenay, J. O'M. Bockris, J. Electrochem. Soc. 134, 841 (1987).
12. Y. Sakai et al., Can. J. Chem. 66, 1853 (1988).
13. G. Lin et al., Appl. Phys. Lett. 55, 386 (1989).
14. J. Augustynski, G. Calzaferri, J. Courvoisier, M. Graetzel, in Proceedings of the 11th World Hydrogen Energy Conference, T. N. Veziroglu, C.-J. Winter, J. P. Baselt, G. Kreysa, Eds. (DECHEMA, Frankfurt, Germany, 1996), pp. 2378-2387.
15. K. A. Bertness et al., App. Phys. Lett. 65, 989 (1994).
16. J. R. Bolton et al., Nature 316, 495 (1985).
17. S. R. Kurtz et al., J. Appl. Phys. 68, 1890 (1990).
18. K. A. Bertness et al., in AIP Conference Proceedings No. 306, R. Noufi and H. Ullal, Eds. (American Institute of Physics, New York, 1994), p. 100.
19. O. Khaselev and J. A. Turner, in preparation.
20. 2 solution. A single-compartment cell was used. Although the electrodes were spatially separated, no attempt was made to separate the products of the anode and cathode reactions.
21. 2. A recent publication (28) has shown that the platinum not only acts as a catalyst for hydrogen evolution but also drastically reduces the corrosion reaction of a similar III-V compound, indium phosphide. We would expect that platinum would offer a comparable corrosion-inhibiting mechanism here.
22. 2, a practical limit for electrolysis. The evolution of gas bubbles on the illuminated surface is also an issue, as these bubbles will scatter light, reducing the efficiency. Given this limitation as well as problems regarding the amount of catalyst and system design issues, a more realistic limit as to the amount of light concentration that can be used for photoelectrolysis is in the range of 10 to 20 suns.
23. The gas products of the photoelectrolysis were analyzed with a UTI-100C mass spectrometer. A sealed cell was used, connected directly to the high-vacuum chamber of the mass spectrometer via a gas inlet system. Before being sealed, the cell was purged for several minutes with nitrogen to remove any oxygen. The cell was then sealed, and the photoelectrolysis reaction was run for several hours. The external current was monitored with an ammeter. Periodically, the gas mixture from the upper part of the cell was sampled by the mass spectrometer system. The same cell was used and the same experimental technique was repeated with the use of two platinum electrodes at the same external current. Within experimental error (∼±20%), the results were the same, indicating stoichiometric water splitting.
24. For 100% electrolysis efficiency, this calculation is identical to Bolton's calculation of efficiency (29). For the size of these samples and the amount of hydrogen and oxygen being generated, a calculation using external current flow is far more accurate.
25. M. F. Weber and M. J. Dignam, Int. J. Hydrogen Energy 11, 225 (1986).
26. _, J. Electrochem. Soc. 131, 1258 (1984).
27. S. Kocha, D. Montgomery, M. Peterson, J. A. Turner, Sol. Energy Mater. Sol. Cells, in press.
28. P. Bogdanoff, P. Friebe, N. Alonso-Vante, J. Electrochem. Soc. 145, 576 (1998).
29. J. R. Bolton, Solar Energy 57, 37 (1996).
30. We thank S. Kurtz and J. Olson for the tandem cell samples and A. Dillon for help with the mass spectrometer measurements. This work was supported by the Hydrogen Program of the U.S. Department of Energy.