Controllable 1D and 2D Cobalt Oxide and Cobalt Selenide Nanostructures as Highly Efficient Electrocatalysts for the...

The relationship between controllable morphology and electrocatalytic activity of Co₃ O₄ and CoSe₂ for the oxygen evolution reaction (OER) was explored in alkaline medium. Based on the time-dependent growth process of cobalt precursors, 1D Co₃ O₄ nanorods and 2D Co₃ O₄ nanosheets were successfully synthesized through a facile hydrothermal process at 180 °C under different reaction times, followed by calcination at 300 °C for 2 h. Subsequently, 1D and 2D CoSe₂ nanostructures were derived by selenization of Co₃ O₄ , which achieved the controllable synthesis of CoSe₂ without templating agents. By comparing the electrocatalytic behavior of these cobalt-based catalysts in 1 m KOH electrolyte toward the OER, both 2D Co₃ O₄ and 2D CoSe₂ nanocrystals have lower overpotentials and better electrocatalytic stability than that of 1D nanostructures. The 2D CoSe₂ nanosheets require overpotentials of 372 mV to reach a current density of 50 mA cm^-2 with a small Tafel slope of 74 mV dec^-1 . A systematic contrast of the electrocatalytic performances for the OER increase in the order: 1D Co₃ O₄ <2D Co₃ O₄ <1D CoSe₂ <2D CoSe₂ . This work provides fundamental insights into the morphology-performance relationships of both Co₃ O₄ and CoSe₂ , which were synthesized through the same approach, providing a solid guide for designing OER catalysts.