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

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 Co3O4-based catalyst with nitrogen-doped porous carbon material as the support,prepared by pyrolysis of porous polyurea(PU) with Co(NO3)2immobilized 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 H2O-acetone at room temperature.By immersing PU in an aqueous solution of Co(NO3)2at room temperature,a cobalt coordinated polymer composite,Co(NO3)2/PU,was obtained,which was heated at 500℃ in air for 2 h to get a hybrid,Co3O4/NC,consisting of Co3O4nanocrystals and sp2-hybridized N-doped carbon.Using this Co3O4/NC as a catalyst in OER,a current density of10 mA·cm-2was readily achieved with a low overpotential of 293 mV with a Tafel slope of87 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.