Thionine coated electrode for photogalvanic cells

• Published in: Nature (London) Vol. 282; no. 5741; pp. 793 - 797
• Main Authors: Albery, W. John, Foulds, Andrew W, Hall, Keith J, Hillman, A. Robert, Egdell, Russell G, Orchard, Antony F
• Format: Journal Article
• Language: English
• Published: 20-12-1979
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/282793a0

The characteristics of a thionine-coated illuminated electrode in a photogalvanic cell intended for solar energy conversion are investigated. Pt and SnO2 electrodes were coated with a stable layer of thionine by holding them at 1.1 to 1.5 V in a thionine solution for several minutes, and the electrode kinetics of various redox couples were examined. Current-voltage curves indicate that the reductions of thionine and its disulphonated derivative are reversible on a clean Sn or Pt electrode and nearly reversible on a coated electrode, while the coating has little effect on the reduction of quinone. For inorganic couples, the coating is found to greatly reduce the kinetics of Fe(III), Fe(CN)6(-4), Ru(2,2 prime bipyridine)3(+3) and Ce(IV) reduction. Coating voltages and times are also found to affect electrode kinetics. The inhibition of inorganic reduction by the coating is explained by the blockage of single electron transfers to the ion. It is concluded that the thionine-coated electrode has the required selectivity to act as the illuminated electrode in an iron-thionine galvanic cell.