Bis(histidine)/Bis(Imidazole) Heme Complex — Polymer Electrolyte Fuel Cell Application as an Alternative Cathode Electrode Catalyst —

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We focus on a variant of the heme protein, i.e., the recently discovered neuroglobin (NHb) and cytoglobin (CHb), looking for clues with regard to possible applications in polymer electrolyte fuel cells (PEFCs), in a quest to design nanomaterials that would replace the expensive platinum catalysts used in PEFC electrodes. The active heme sites of these two new members of the globin superfamily display a functionally-relevant heme iron atom, whose sixth coordination site is occupied by an endogenous (internal) protein ligand, in the absence of exogenous (external) ligands, such as O₂, CO, and NO. Density Functional Theory (DFT)-based calculation results indicate a possible means of controlling the adsorption and desorption on adsorbed O₂ through the endogenous protein ligand occupying the sixth coordination site of the central iron atom in the heme structure. [DOI: 10.1380/ejssnt.2005.233]