N-doped carbon dots regulate porous hollow nickel-cobalt sulfide: High-performance electrode materials in supercapacitor and enzymeless glucose sensor

Abstract

Transition metal sulfides (TMSs) are expected to be a new type of electrode material due to their excellent electrochemical activity. However, the poor capacity retention and stability of TMSs are obstacles to their practical application. Here, the porous hollow nickel-cobalt sulfides are fabricated via a simple water bath followed by anion exchange, which can be regulated by N-doped carbon dots (NCDs). Newly designed porous hollow structure provides more active sites, a cavity for storing electrolytes, and optimized electron/ion diffusion pathways. Then, the Ni-Co ratio and the NCDs doping mass are optimized, and the as-prepared NCDs/Ni2Co1S-50 displays a specific capacity of 764.1 C g−1 at 1 A g−1. A hybrid supercapacitor based on NCDs/Ni2Co1S-50 achieves an outstanding energy/power density (73 mWh cm−2/1.39 W cm−2) and exhibits favorable cyclic performance (96.5% maintain for 10 000 times). In addition, a glucose sensor based on NCDs/Ni2Co1S-50 modified glassy carbon electrode (GCE) is designed, with a wide detection range of 1 × 10−5-5 × 10−3 M and a low detection limit of 3.8 × 10−7 M (S/N = 3). The excellent electrochemical performance demonstrates the effectiveness of the manufacturing strategy of adjusting the properties of hollow-structured metal sulfides through carbon dots and provides a novel way to design new nanocomposite materials used for the multi-functional field.