Immobilization of FeFe hydrogenase mimics onto carbon and gold electrodes by controlled aryldiazonium salt reduction: an electrochemical, XPS and ATR-IR study

A dithiolate-bridged hexacarbonyldiiron complex was synthesized from the reaction of the N-hydroxysuccinimide (NHS) ester of lipoic acid with Fe3(CO)12 in toluene. This mimic of the active site of FeFe hydrogenases could be covalently attached, using an NHS ester route, to carbon or gold electrode first decorated with amino functions. Once grafted this complex catalyzes hydrogen electro-evolution under strongly acidic conditions but is rapidly inactivated. We could evidence that the activity loss was due to the elimination of the carbonyl ligands rather than a leaching of the catalyst as a consequence of hydrolysis of the amide linkages.