Spinel Iron Oxide Nanoparticles Decorated on Pyridinic‐N and Carbon Surface: A Highly Efficient Inexpensive Electrocatalyst for Oxygen Reduction and Oxygen Evolution Eeactions

Abstract

AbstractThe oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) have been established widely owing to their significance in water electrolyzers, fuel cells and metal‐air batteries. The ORR electron transfer number have been calculated from K−L plot as 3.1 (Fe3O4/ N2−xC‐500), 3.8 (Fe3O4/N2−xC‐600), 3.6 (Fe3O4/N2−XC‐700) and 3.2 (Fe3O4/N2−XC‐800). At 3 mA cm−2, the half‐wave potential has been determined as 0.66 V (Fe3O4/N2−XC‐500), 0.76 V (Fe3O4/N2−XC‐600), 0.75 V (Fe3O4/N2−XC‐700) and 0.68 V (Fe3O4/N2−XC‐800). At 10 mA cm−2, the OER potential for Fe3O4/N2−XC‐500, Fe3O4/N2−XC‐600, Fe3O4/N2−XC‐700 and Fe3O4/N2−XC‐800 electrocatalysts were determined as 1.61, 1.58, 1.62 and 1.66 V, respectively. The ORR: OER electrode potentials were found to be 0.95, 0.82, 0.87 and 0.93 V for Fe3O4/N2−XC‐500, Fe3O4/N2−XC‐600, Fe3O4/N2−XC‐700 and Fe3O4/N2−XC‐800 electrocatalysts, respectively by using solar to hydrogen fuel device conversion scale. The ORR/OER Tafel slopes were calculated as 78/89 mV/dec (Fe3O4/N2−XC‐500), 73/78 mV/dec (Fe3O4/N2−XC‐600), 76/83 mV/dec (Fe3O4/N2−XC‐700) and 79/98 mV/dec (Fe3O4/N2−XC‐800). Among the new born oxygen vacancy (Vo) spinel oxide electrocatalysts, Fe3O4/N2−XC‐600 exhibit an exceptional oxygen electrode activity with 0.82 V in 0.1 M KOH due to robust double exchange interconnection (DEI) between stable magnetite spinel Fe3O4 and N2−XC.