Reduced graphene oxide supported Fe₂B as robust catalysts for oxygen reduction reaction

Transition metal borides have great potential to be low-cost, high-performance catalysts for novel energies despite the synthesis is rather difficult. In this paper, the reduced graphene oxide (rGO) supported iron boride (Fe₂B/rGO) based catalysts are synthesized by a facile reduction method. The successful synthesis of Fe₂B is confirmed by X-ray diffraction, scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), X-ray photo-electron spectroscopy (XPS) and other tests. HRTEM tests showed that the constructed Fe₂B was embedded in the rGO, where B played the role of coordination atoms which could regulate the electronic structure of the catalysts and improve the catalytic performance towards oxygen reduction reaction (ORR). The electrochemistry tests showed that the peak current intensity of the Fe₂B/rGO catalyzed ORR could be reached up to 7.6 mA/cm², which surpassed that of the Pt/C (20 wt%) catalyst. The current intensity can be kept at 82.47% after continuous running 20,000 s, which is higher than the Pt/C catalyst (79.4%). The onset potential reaches up to 0.95 V, which is only 0.06 V lower than that of Pt/C (20 wt%) catalyst. Both RDE and RRDE tests confirmed that the Fe₂B/rGO catalyzed ORR major happed through 4-electron pathway. The redistributed electron between iron and boron atoms promoted the happening of ORR on Fe₂B/rGO catalysts. The results of this work provide a novel way to develop high performance transition metal boride based catalysts for ORR.