Electrocatalytic Oxygen Reduction in Alkaline Medium at Graphene-Supported Silver-Iron Carbon Nitride Sites Generated During Thermal Decomposition of Silver Hexacyanoferrate

Silver-iron carbon nitride, which has been prepared by pyrolysis (under inert atmosphere) of silver hexacyanoferrate(II) deposited on graphene nanoplatelets, is considered here as electrocatalyst for oxygen reduction in alkaline medium (0.1 M potassium hydroxide electrolyte) in comparison to simple silver nanoparticles and iron carbon nitride (prepared separately in a similar manner on graphene nanoplatelets). The performance of catalytic materials has been examined using such electrochemical diagnostic techniques as cyclic voltammetry and rotating ring-disk electrode voltammetry. Upon application of the graphene nanoplatelet-supported mixed silver-iron carbon nitride catalyst, the reduction of oxygen proceeds at more positive potentials, as well as the amounts of hydrogen peroxide (generated during reduction of oxygen at potentials more positive than 0.3 V) are lower relative to those determined at pristine silver nanoparticles and iron carbon nitride (supported on graphene nanoplatelets), when they have been examined separately. The enhancement effect shall be attributed to high activity of silver toward the reduction/ decomposition of H2O2 in basic medium. Additionally, it has been observed that the systems based on carbon nitrides show considerable stability due to strong fixation of metal complexes to CN shells.