CoS2 Nanoparticles Embedded in Covalent Organic Polymers as Efficient Electrocatalyst for Oxygen Evolution Reaction with Ultralow Overpotential

Cobalt disulfide (CoS2 ) has been explored as attractive electrocatalyst for oxygen evolution reaction (OER). However, bulk CoS2 sheets have limited catalytic activity due to low exposure of active sites. Herein, through an in-situ vulcanization approach, CoS2 nanoparticles are embedded into bipyridine-containing covalent organic polymer (BP-COP). The as-prepared nanocomposite CoS2 @BP-COP exhibits high catalytic activity toward OER with an ultra-low overpotential of 270 mV (vs. RHE) at a current density of 10 mA cm-2 , a small Tafel slope of 36 mV dec-1 , and an excellent durability for 24 h without decay. The surface of CoS2 is partially converted into CoOOH to form CoS2 /CoOOH as active sites under OER conditions. CoS2 @BP-COP displays superior OER catalytic activity to CoS2 nanosheets and commercially available RuO2 under the same conditions. The outstanding OER performance activity of CoS2 @BP-COP could be attributed to the uniform and small particle sizes of CoS2 /CoOOH distributed in BP-COP.