Ultra-small Co/CoO nanoparticles dispersed on N-doped carbon nanosheets for highly efficient electrocatalytic oxygen evolution reaction

Abstract

In this paper, we report a facile strategy to synthesize Co-BDC-NH2 material, which is used as a precursor towards an excellent OER electrocatalyst by thermal annealing in nitrogen. Ultra-small Co/CoOx nanoparticles were uniformly dispersed on the rhombus N-doped carbon (NC) nanoflakes. Transmission electron microscopic, X-ray diffraction spectrometric, and X-ray photoelectron spectroscopic analyses revealed the coexistence of metallic Co and Co oxides nanoparticles. It was found that Co/CoOx@NC obtained at 500 °C annealing temperature exhibited the highest electrocatalytic OER activity, with 307 and 375 mV overpotential to achieve 10 and 100 mA cm−2 current densities. Besides, thanks to the in-situ annealing process, Co/CoOx@NC showed excellent catalytic stability with 97.4% current density retention after 24 h electrolysis at 1.66 V vs. RHE electrode potential. Further investigations revealed that the ultra-small Co/CoOx nanoparticles distributed on N-doped carbon template contribute significantly towards OER electrocatalysis through enlarging the activity surface areas and enhancing the intrinsic electrochemical activity due to the presence of metallic Co.