Metal-Organic Framework Template Derived Porous CoSe2 Nanosheet Arrays for Energy Conversion and Storage

Bifunctional bamboo-like CoSe2 arrays for high-performance asymmetric supercapacitor and electrocatalytic oxygen evolution

Bifunctional bamboo-like CoSe₂ arrays are synthesized by thermal annealing of Co(CO₃)_0.5OH grown on carbon cloth in Se atmosphere. The CoSe₂ arrays obtained have excellent electrical conductivity, larger electrochemical active surface areas, and can directly serve as a binder-free electrode for supercapacitors and the oxygen evolution reaction (OER). When tested as a supercapacitor electrode, the CoSe₂ delivers a higher specific capacitance (544.6 F g^-1 at current density of 1 mA cm^-2) compared with CoO (308.2 F g^-1) or Co₃O₄ (201.4 F g^-1). In addition, the CoSe₂ electrode possesses excellent cycling stability. An asymmetric supercapacitor (ASC) is also assembled based on bamboo-like CoSe₂ as a positive electrode and active carbon as a negative electrode in a 3.0 M KOH aqueous electrolyte. Owing to the unique stucture and good electrochemical performance of bamboo-like CoSe₂, the as-assembled ACS can achieve a maximum operating voltage window of 1.7 V, a high energy density of 20.2 Wh kg^-1 at a power density of 144.1 W kg^-1, and an outstanding cyclic stability. As the catalyst for the OER, the CoSe₂ exhibits a lower potential of 1.55 V (versus RHE) at current density of 10 mA cm^-2, a smaller Tafel slope of 62.5 mV dec^-1 and an also outstanding stability.

Rational Construction of Hollow Core-Branch CoSe2 Nanoarrays for High-Performance Asymmetric Supercapacitor and Efficient Oxygen Evolution

Metal selenides have great potential for electrochemical energy storage, but are relatively scarce investigated. Herein, a novel hollow core-branch CoSe₂ nanoarray on carbon cloth is designed by a facile selenization reaction of predesigned CoO nanocones. And the electrochemical reaction mechanism of CoSe₂ in supercapacitor is studied in detail for the first time. Compared with CoO, the hollow core-branch CoSe₂ has both larger specific surface area and higher electrical conductivity. When tested as a supercapacitor positive electrode, the CoSe₂ delivers a high specific capacitance of 759.5 F g^-1 at 1 mA cm^-2 , which is much larger than that of CoO nanocones (319.5 F g^-1 ). In addition, the CoSe₂ electrode exhibits excellent cycling stability in that a capacitance retention of 94.5% can be maintained after 5000 charge-discharge cycles at 5 mA cm^-2 . An asymmetric supercapacitor using the CoSe₂ as cathode and an N-doped carbon nanowall as anode is further assembled, which show a high energy density of 32.2 Wh kg^-1 at a power density of 1914.7 W kg^-1 , and maintains 24.9 Wh kg^-1 when power density increased to 7354.8 W kg^-1 . Moreover, the CoSe₂ electrode also exhibits better oxygen evolution reaction activity than that of CoO.

Efficient catalysts for oxygen evolution derived from cobalt-based alloy nanochains

One-dimensional nanomaterials are widely used in electrocatalysis owing to their high charge transfer efficiency.