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

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