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 Co₃O₄-based catalyst with nitrogen-doped porous carbon material as the support, prepared by pyrolysis of porous polyurea (PU) with Co(NO₃)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 H₂O-acetone at room temperature. By immersing PU in an aqueous solution of Co(NO₃)₂ at 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 Co₃O₄ nanocrystals and sp²-hybridized N-doped carbon. Using this Co₃O₄/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.

Key words: Porous polyurea, N-doped carbon-Co₃O₄ hybrid, Oxygen evolution, Catalyst, Electrolysis, Electrochemistry

摘要： 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)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 H₂O-acetone at room temperature. By immersing PU in an aqueous solution of Co(NO₃)₂ at 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 Co₃O₄ nanocrystals and sp²-hybridized N-doped carbon. Using this Co₃O₄/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.

关键词: Porous polyurea, N-doped carbon-Co₃O₄ hybrid, Oxygen evolution, Catalyst, Electrolysis, Electrochemistry