A semiconductor/molecular catalyst hybrid photoanode with FeOOH as an electron transfer relay

A Fe₂ O₃ /FeOOH/poly-Ru(bda)(vpy) (bda = 2,2'-bipyridine-6,6'-dicarboxylate,vpy = 4-vinylpyridine) photoanode has been fabricated by electropolymerization of molecular Ru(bda)(vpy) catalyst on FeOOH modified Fe₂ O₃ , in which a thin layer of FeOOH replicates the role of tyrosine residue in PSII as an efficient electron transfer mediator. The ternary hybrid photoanode produced a 2.4 times higher photocurrent density than that of previously reported Fe₂ O₃ /poly-Ru(bda)(vpy) under AM 1.5 G illumination and displayed a negative shift on the onset potential by 100 mV. In addition, the Fe₂ O₃ /FeOOH/poly-Ru(bda)(vpy) exhibited long-term stability for at least 10 h with a Faraday efficiency of ∼96%. The high performance shown here was attributed to the improved charge separation between excited semiconductor and the catalyst caused by FeOOH mediated electron transfer on the electrode surface.