Photoelectrochemical Water Oxidation by Cobalt Cytochrome C Integrated-ATO Photoanode

Here, we report the immobilization of Co-protoporphyrin IX (Co-PPIX) substituted cytochrome c (Co-cyt c) on Antimony-doped Tin Oxide (ATO) as a catalyst for photoelectrochemical oxidation of water. Under visible light irradiation (λ > 450 nm), the ATO-Co-cyt c photoanode displays ~6-fold enhancement in photocurrent density relative to ATO-Co-PPIX at 0.25 V vs. RHE at pH 5.0. The light-induced water oxidation activity of the system was demonstrated by detecting evolved stoichiometric oxygen by gas chromatography, and incident photon to current efficiency was measured as 4.1% at 450 nm. The faradaic efficiency for the generated oxygen was 97%, with a 671 turnover number (TON) for oxygen. The current density had a slow decay over the course of 6 h of constant irradiation and applied potential, which exhibits the robustness of catalyst-ATO interaction

Improved Electro- and Photocatalytic Water Reduction by Confined Cobalt Catalysts in Streptavidin

Incorporation of biotinylated aminopyridine cobalt complexes derived from the triazacyclononane scaffold into the streptavidin protein leads to formation of artificial metalloenzymes for water reduction to hydrogen. The synthesized artificial metalloenzymes have lower overpotential (at the half-peak up to 100 mV) and higher photocatalytic hydrogen evolution activity (up to 14- and 10-fold increase in TOF and TON, respectively, at pH 12.5) than the free biotinylated cobalt complexes. 1H-NMR, EPR and XAS highlight the presence of the metal complexes upon supramolecular attachment to the streptavidin. pHdependent catalytic studies and molecular dynamics (MD) simulations suggest that the increase in the catalytic activity could be induced by the protein residues positioned close to the metal centers. These findings illustrate the ability of the biotin−streptavidin technology to produce artificial metalloproteins for photo- and electrocatalytic hydrogen evolution reaction