Nitrogen containing carbon materials have been reported to show catalytic activities such as an oxygen reduction reaction (O2 + 4H+ + 4e- → 2H2O, ORR) in fuel cells. Among several types of nitrogen species in carbon materials, pyridinic nitrogen (nitrogen atom bound to two C atoms) was found to create ORR active sites in our previous work. We then try to clarify the role of pyridinic nitrogen by using moel catalysts composed of pyridinic nitrogen-containing aromatic molecules such as dibenz[a,c] acridine (DA). The pyridinic nitrogen is readily protonated to pyridinium species, pyri-NH+, in acidic electrolytes, while it is reduced to NH species by applying potentials in the presence of O2. No reduction of pyri-NH+ took place in the absence of O2, indicating that the O2 adsorption is coupled with the reduction of pyri-NH+. We currently conclude that the redox potential of the pyri-NH+ govern the catalytic acitivity of ORR.

Mechanism of oxygen reduction reaction on N-doped carbon catalysts

ACS Fall 2021

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