Immobilization of cobalt oxide nanoparticles on porous nitrogen-doped carbon as electrocatalyst for oxygen evolution

Abstract

Highly efficient and robust electrocatalysts have been in urgent demand for oxygen evolution reaction (OER). For this purpose, high-cost carbon materials, such as graphene and carbon nanotubes, have been used as supports to metal oxides to enhance their catalytic activity. We report here a new Co 3 O 4 -based catalyst with nitrogen-doped porous carbon material as the support, prepared by pyrolysis of porous polyurea (PU) with Co(NO 3 ) 2 immobilized on its surface. To this end, PU was first synthesized, without any additive, through a very simple one-step precipitation polymerization of toluene diisocyanate in a binary mixture of H 2 O-acetone at room temperature. By immersing PU in an aqueous solution of Co(NO 3 ) 2 at room temperature, a cobalt coordinated polymer composite, Co(NO 3 ) 2 /PU, was obtained, which was heated at 500 °C in air for 2 h to get a hybrid, Co 3 O 4 /NC, consisting of Co 3 O 4 nanocrystals and sp 2 -hybridized N-doped carbon. Using this Co 3 O 4 /NC as a catalyst in OER, a current density of 10 mA·cm −2 was readily achieved with a low overpotential of 293 mV with a Tafel slope of 87 mV·dec −1 , a high catalytic activity. This high performance was well retained after 1000 recycled uses, demonstrating its good durability. This work provides therefore a facile yet simple pathway to fabrication of a new transition metal oxides-based N-doped carbon catalyst for OER with high performance.