A New Heterogeneous Photocathode Based on Ruthenium(II)quaterpyridinium Complexes at TiO2 Particles

We have studied a new type of heterogeneous composite electrode featuring a ruthenium(II)−quaterpyridinium complex (Ru3PHOS) bearing six phosphonate groups for strong chemisorption on TiO2. Ru3PHOS@TiO2 has then been deposited on microscopy glass slides using Ag-doped epoxy glue. Nanomolar amounts of palladium have been electrodeposited onto the Ru3PHOS@TiO2. To our surprise, we have observed the deposition of carbon needles onto the composite material when (photo)electrochemically reducing bicarbonate from aqueous buffers.