Self assembled monolayer (SAM) of metallomacrocycle as a synthetic cathode catalyst for a hybrid bio-fuel-cell

A hybrid bio-fuel-cell (HBFC) has one electrode with an enzyme catalyst and another with a synthetic catalyst. A new cobalt(II) porphyrin, Col, was synthesized as an oxygen reduction catalyst for a cathode in a HBFC. Col has a covalently attached phosphonate group, which gives Col affinity for metal oxide so it can form a self-assembled monolayer (SAM) on an electrode with an oxide surface. Voltammetry of a SAM of Col on an indium tin oxide (ITO) electrode in aqueous 0.01 molar TFMSA solution equilibrated with 1 atmosphere of Argon showed a surface charge corresponding to a monolayer of Col. In the same triflic acid solution equilibrated with oxygen, a bare ITO electrode did not reduce oxygen at any potential, but the same ITO electrode after coated with a SAM of Col exhibited substantial oxygen electro reduction current, which began at 0.65 V versus NHE and was not affected by the presence of methanol. This selectivity indicates that a SAM of Col is a promising catalyst for a cathode, which can selectively scavenge oxygen from biological sera which also contains alcohols and other organic species.