Preparation of bimetal-based FeNi-N/C catalyst and its electrocatalytic oxygen reduction performance

Abstract

A kind of bimetal-based FeNi-N/C catalysts were prepared by combining ultrasonic reaction and high temperature heat treatment using dicyandiamide (DCD) as nitrogen source, FeCl3·6H2O and Ni(OAc)2·4H2O as bimetal source, BP2000 as carbon carrier. The composition and structure of the catalysts as-prepared were characterized by XRD, FT-IR and XPS. The catalytic activity of the catalysts on the oxygen reduction reaction(ORR) under alkaline conditions were tested by using linear sweep voltammetry (LSV) with a rotating disk electrode, and the prepared conditions, active site composition, the stability and methanol resistance of the as-prepared catalysts and the kinetic ORR mechanism were studied successively. The results show that the best FeNi-N/C-800 catalytic activity for ORR with the onset potential of 0.965 V (vs. RHE). The number of transferred electrons in catalytic ORR process is between 3.59 and 3.98, indicating the 4e− dominated ORR mechanism and a direct conversion process from O2 into H2O. The nature of the metal and the heat treatment temperature are important key factors in the preparation of the catalyst. From this work, Ni can be regarded as a catalyst for N and metal Fe atoms into the carbon support, and Fe-Nx-C (Fe bonds with pyridine-N) is the main active sites of the catalyst FeNi-N/C and a synergistic effect of the two sites of Fe-Nx-C and Ni-Nx-C enhances their catalytic activity for ORR further.