LAUSR

Abstract Currently, it remains a big challenge for developing bifunctional oxygen electrocatalysts with high performance and low cost towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Co 3 O 4 as one kind of non-precious metal electrocatalysts has shown promising bifunctional performance in alkaline media, which is greatly influenced by the average particle size. Here, size-controlled synthesis of Co 3 O 4 nanoparticles loaded on N-doped reduced graphene oxide (RGO) was performed by adjusting the Co 2+ initial feed concentration, and five Co 3 O 4 /N-RGO catalysts with different particle sizes were obtained. Among the prepared samples, the Co 3 O 4 /N-RGO catalyst with the average particle size of ∼12.2 nm displays the best bifunctional oxygen electrocatalytic activities with the ΔE (E OER,10mAcm-2 -E ORR,–3mAcm-2 ) value of 0.75 V, which is the lowest value for the Co-based bifunctional electrocatalysts as reported in the literatures. The catalyst of Co 3 O 4 nanoparticles on N-doped RGO is a promising bi-functional catalyst for fuel cell and water splitting systems.