Photoinduced electron transfer by coordination chemical pathways across pyrite/electrolyte interfaces

Experiments are presented which show that, in the case of pyrite (FeS{sub 2}), interfacial transition-metal bridge complexes formed by attaching -O-, -CN-, or -CO- groups facilitate electronic charge transfer more efficiently by inner-sphere mechanisms (strong interaction) than may occur by tunneling (weak interaction). This is advantageous concerning electrode stability and catalytic activity. The described experiments also show that appropriate chemical surface modifications can channel photogenerated charge carriers through the interface of d-character materials at a high photocurrent density ({approximately}30 mA cm{sup {minus}2}) and with good stability. Individual -CN- groups attached to the FeS{sub 2} interface pass photogenerated charge carriers at least 10{sup 6} times before a side reaction occurs. New models have to be developed to describe the semiconductor/electrolyte interface in cases with strong chemical interaction. A first qualitative picture is presented. 34 refs., 9 figs., 1 tab.