Phytic acid-assisted synthesis of ultrafine NiCo2S4 nanoparticles immobilized on reduced graphene oxide as high-performance electrode for hybrid supercapacitors

Abstract

Incorporating graphene with transition metal sulfides nanoparticles (NPs) holds great potential as a high performance battery-type electrode for hybrid supercapacitors (HSCs). However, the poor interfacial contact between NPs and graphene sheets usually leads to compromised capacitance and stability of electrode materials. In order to tackle this problem, eco-friendly phytic acid (PA) is used as a bridging connection between graphene and NiCo2S4 NPs via the six phosphate groups of PA to afford NiCo2S4 NPs immobilized firmly on phytic acid modified reduced graphene oxide (PRGO) sheets. In addition, the morphology of NiCo precursor could be easily tuned by the addition of PA. Benefiting from the morphology and composition, the prepared NiCo2S4/PRGO hybrid battery-type electrode exhibits excellent electrochemical performance with high capacitance (1090 F g−1 at 2 A g−1), good rate performance (76.1% of the capacitance can be retained from 2 to 20 A g−1) and enhanced cycling stability. Moreover, a HSC device is fabricated using NiCo2S4/PRGO hybrid as positive electrode and active carbon (AC) as negative electrode, which exhibits a prominent energy density of 27.5 Wh kg−1 at a high power density of 446.5 W kg−1. The utilization of PA could offer a new avenue for the design of transition metal sulfides/PRGO hybrid for electrochemical or electrocatalytic applications.