ABSTRACT: The oxygen reduction reaction (ORR) continues to be a reaction of interest because of its importance to biologically relevant reactions and as a pathway for meeting increasing energy demands through fuel cell applications. Developing earth-abundant molecular mimics of metalloprotein active sites can offer insight into fundamental biological processes, as well as, offer a green alternative to the anthraquinone process for the synthesis of H2O2 if selectivity can be achieved. We have conducted a series of mechanistic investigations on the electrocatalytic reduction of dioxygen (O2) to hydrogen peroxide (H2O2) by a molecular manganese (III) complex with a tetradentate dianionic bipyridine-based ligand. Electrochemical characterization suggests that upon reduction to Mn(II), the coordinated phenolate moieties of the ligand are protonated with a Nernstian dependence on the added proton source. The resultant species is competent for the reduction of dioxygen to H2O2 with 81±4% Faradaic efficiency. Spectrochemical stopped-flow analyses utilizing decamethylferrocene as a reductant uncovered a divergence in mechanism based of the nature of the reductant, although H2O2 is still generated when homogeneous reductant is used. The use of quinol as a redox mediator and the effect of 1-methylimidazole as an axial ligand on O2 binding and reduction have also been examined.

Electrocatalytic reduction of dioxygen to hydrogen peroxide by a molecular manganese complex with a bipyridine-containing Schiff base ligand

2019 Fall National Meeting

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