Hydrogen peroxide transition metal macrocyclic

Electrocatalytic ORR carries out in three pathways the 1-electron transfer pathway, producing superoxide ion the 2-electron transfer pathway, producing hydrogen peroxide and the 4-electron transfer pathway, producing water. In a non-aqueous aprotic solvent system, a room-temperature ionic liquid system, and on specific transition-metal, macrocyclic-compounds-coated graphite electrodes in alkaline solutions, 1-electron reduction can be observed. Carbon materials, quinone and derivatives, mono-nuclear cobalt macrocyclic compounds, and some chalcogenides can only catalyze 2-electron ORR. Noble metal, noble metal alloy materials, iron-macrocyclic complexes, di-nuclear cobalt macrocyclic complexes, some chalcogenides, and transition-metal carbide-promoted Pt catalysts can catalyze 4-electron reduction. 

More importandy, extensive studies have shown that the central transition metals would dictate the oxygen reduction pathways on these M-N4 macrocyclic complexes. It has been found that most C0-N4 macrocyclic complexes promote only 2e reduction of oxygen to produce hydrogen peroxide as final products [18, 50, 81, 92, 93]. In contrast, Fe-N4 macrocyclic complexes are found to likely promote 4e reduction of oxygen to produce water with cleavage of 0-0 bond [18, 50, 81, 92, 93]. 

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