Molecularly engineered oxygen deficient magnetite decorated carbon as electrocatalysts for oxygen reduction reaction

Abstract

Herein, we report the in situ synthesis of poly (ferrocene-urea) (PFUA) by reacting ferrocene diacylazide and tris (4-aminophenyl) amine. The formation of urea linkages between the precursors was confirmed by Fourier transform Infrared (FTIR) spectroscopy. The synthesized PFUA was pyrolyzed at different temperatures under Argon atmosphere to obtain hematite at 600 °C and magnetite embedded N-doped carbons at 800 and 1000 °C. Both hematite and magnetite was found to have particulate morphology embedded on porous N-doped carbon. The N-doping into the carbon matrix was confirmed by X-ray photoelectron spectroscopy (XPS). Further, their electrocatalytic activity towards oxygen reduction reaction (ORR) was carried out under standard conditions. PFUA pyrolyzed at 800 °C was found to exhibit better ORR activity than the other samples. The improved electrocatalytic activity toward ORR can be ascribed to the reductive environment generated during the thermal treatment of the urea linkages (formed between FDA and TAPA) which controls the structural transformation of the hematite phase to magnetite phase of iron oxide with creation of oxygen vacancies with improved Fe2+ to Fe3+ ratio