3D carbon coated NiCo2S4 nanowires doped with nitrogen for electrochemical energy storage and conversion

Three-dimensional (3D) carbon-coated NiCo<inf>2</inf>S<inf>4</inf> nanowires structures doped with nitrogen are used for energy storage and conversions. The nitrogen doping in both the carbon layer and NiCo<inf>2</inf>S<inf>4</inf> nanowires enhances the electrochemical performances. Here, an easily scalable and simple temperature treatment has been used to decorate carbon-coated NiCo<inf>2</inf>S<inf>4</inf> nanowires with nitrogen doping (N–C@NiCo<inf>2</inf>S<inf>4</inf> NWs) in 3D carbon architecture (carbon cloth). Benefiting from the nitrogen doping and ultrathin carbon layer, the as-prepared 3D N–C@NiCo<inf>2</inf>S<inf>4</inf> NWs electrode exhibits the superior electrochemical performance for both asymmetric supercapacitor and electrocatalytic water splitting. An asymmetric supercapacitor assembled by the N–C@NiCo<inf>2</inf>S<inf>4</inf> NWs and active carbon electrodes achieves a high energy density of 1.72 mWh cm⁻³ (68.87 Wh kg⁻¹) under a power density of 10.63 mW cm⁻³ (425 W kg⁻¹) with 90.1% retention of initial capacitance after 10,000 cycles. When employed as the electrocatalyst, the N–C@NiCo<inf>2</inf>S<inf>4</inf> NWs show high activities towards electrocatalytic water splitting.