Electrocatalytic reduction of CO in water by a -functionalized Ni-cyclam complex grafted onto carbon.

We present here a novel strategy based on the covalent grafting of a -functionalized Ni-cyclam complex onto glassy carbon to achieve heterogeneous electrocatalytic CO reduction in neutral water at low overpotential (-500 mV NHE), with moderate turnover number (TON = 454), high selectivity (85% CO produced) and good faradaic efficiency (56% CO). Direct comparison with the -functionalized Ni-cyclam analogue highlights the benefits of this approach in terms of CO electroreduction.

Electrochemical Investigations of Hydrogenases and Other Enzymes That Produce and Use Solar Fuels.

Many enzymes that produce or transform small molecules such as O, H, and CO embed inorganic cofactors based on transition metals. Their active site, where the chemical reaction occurs, is buried in and protected by the protein matrix, and connected to the solvent in several ways: chains of redox cofactors mediate long-range electron transfer; static or dynamic tunnels guide the substrate, product and inhibitors; amino acids and water molecules transfer protons. The catalytic mechanism of these enzymes is therefore delocalized over the protein and involves many different steps, some of which determine the response of the enzyme under conditions of stress (extreme redox conditions, presence of inhibitors, light), the catalytic rates in the two directions of the reaction and their ratio (the "catalytic bias").

Mechanism of O diffusion and reduction in FeFe hydrogenases.

FeFe hydrogenases are the most efficient H-producing enzymes. However, inactivation by O remains an obstacle that prevents them being used in many biotechnological devices. Here, we combine electrochemistry, site-directed mutagenesis, molecular dynamics and quantum chemical calculations to uncover the molecular mechanism of O diffusion within the enzyme and its reactions at the active site.

Electrochemical Measurements of the Kinetics of Inhibition of Two FeFe Hydrogenases by O2 Demonstrate That the Reaction Is Partly Reversible.

The mechanism of reaction of FeFe hydrogenases with oxygen has been debated. It is complex, apparently very dependent on the details of the protein structure, and difficult to study using conventional kinetic techniques. Here we build on our recent work on the anaerobic inactivation of the enzyme [Fourmond et al.

Locally induced and self-induced "electroclick" onto a self-assembled monolayer: writing and reading with SECM under unbiased conditions.

Localized "electroclick" was achieved on azido-terminated self-assembled monolayers using Scanning Electrochemical Microscopy (SECM) in feedback mode, in which the substrate is not electrically connected (unbiased conditions). The method allows both the local immobilization of diverse functional moieties and the monitoring of each modification step at a micrometer scale. Conditions of the "click" coupling reaction were optimized especially to avoid the deposit of metallic copper by the choice of a specific ligand to stabilize the Cu(I) species.

Photocatalytic hydrogen production using models of the iron-iron hydrogenase active site dispersed in micellar solution.

Iron-thiolate complexes of the type [Fe2 (μ-bdt)(CO)6-x P(OMe3 )x ] (bdt=S2 C6 H4 =benzenedithiolate, x≤2) are simplified models of iron-iron hydrogenase enzymes. Recently, we have shown that these water-insoluble organometallic complexes, when included into micelles formed by sodium dodecyl sulfate (SDS), are good catalysts for the electrochemical production of hydrogen in aqueous solutions at pH<6. We herein report that the all-CO derivative [Fe2 (μ-bdt)(CO)6 ] (1), owing to its comparatively low reduction potential, is also a robust molecular catalyst for visible-light-driven production of H2 in aqueous SDS solutions at pH 10.

A generic platform for the addressable functionalisation of electrode surfaces through self-induced "electroclick".

A novel and general strategy for the immobilisation of functional objects onto electrodes is described. The concept is based on the addition of two pendant ethynyl groups onto a bis(pyridyl)amine derivative, which acts as a molecular platform. This platform is pre-functionalised with an N(3)-tagged object of interest by Huisgen cycloaddition to one of the ethynyl groups in biphasic conditions.