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 3 O 4 and CoSe 2 for the oxygen evolution reaction (OER) was explored in alkaline medium. Based on the time‐dependent growth process of cobalt precursors, 1D Co 3 O 4 nanorods and 2D Co 3 O 4 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 2 nanostructures were derived by selenization of Co 3 O 4 , which achieved the controllable synthesis of CoSe 2 without templating agents. By comparing the electrocatalytic behavior of these cobalt‐based catalysts in 1  m KOH electrolyte toward the OER, both 2D Co 3 O 4 and 2D CoSe 2 nanocrystals have lower overpotentials and better electrocatalytic stability than that of 1D nanostructures. The 2D CoSe 2 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 Co 3 O 4 <2D Co 3 O 4 <1D CoSe 2 <2D CoSe 2 . This work provides fundamental insights into the morphology–performance relationships of both Co 3 O 4 and CoSe 2 , which were synthesized through the same approach, providing a solid guide for designing OER catalysts.