Novel photochemical/photoelectrochemical systems based on metal hexacyanoferrates

Abstract

Abstract Electrolyte modification is realized to be a promising route to achieve better efficiencies in solar energy conversion in photoelectrochemical cells. Recent reports by Bocarsly et al. [1,2] and Licht et al. [3,4] have amply demonstrated this aspect wherein maximum efficiency received so far viz. 16.4% has been reported using chalcogenides of Cd as semiconductors in contact with a solution of a mixture of ferro/ferricyanide containing added cyanide ions. Surface modification of the semiconductor, cadmium sulphide/selenide, that takes place as a result of interaction with the redox, giving rise to cadmium hexacyanoferrate, has been considered important in yielding the improved energy efficiency. But interestingly, no attempt to ascertain the role of modifying hexacyanoferrate film formed as a possible photo-energy converter (also) has been made. Many metal hexacyanoferrates themselves semiconductors, being intervalent compounds, are subjects of intensive current research as they hold promise in several applications of sensors, electrochromic devices, catalysis, and most importantly in photo-energy conversion. In this context we report the results of photoresponse studies on indium hexacyanoferrate films on conducting carbon in contact with solutions of Fe(CN) −3 6 . We conclude from these studies that such interfaces under light irradiation indeed give rise to measurable and significant photocurrents whose nature is distinctly different from that obtained in the absence of a redox in solution. The article describes the observations and explains them taking into account photo/photoelectrochemical effects.