Synthesis of nickel hexacyanoferrate nanostructure on carbon cloth with predeposited nickel nanoparticles as precursor for binder-free high-performance supercapacitor electrodes

Highlights: • NiNPs were electrodeposited on carbon cloth. • NiNPs were oxidized by GO to Ni²⁺ in the presence of K₃Fe(CN)₆. • Synthesized Ni-HCF nanocubes were uniformly distributed on carbon cloth. • Mass-loading of Ni-HCF can be easily tuned by adjusting the deposition time. • Ni-HCF/CC demonstrates excellent electrochemical performances. -- Abstract: Transition metal (TM) hexacyanoferrates (TM-HCF) have been proven efficient electrode materials for supercapacitors, especially in neutral electrolyte. In this work, nickel hexacyanoferrate (Ni-HCF) with ultra-high mass-loading was synthesized on carbon cloth (CC) with nickel nanoparticles (NiNPs) as the precursor, which were in-situ converted to Ni-HCF with graphene oxide (GO) as the oxidant and NiNPs as the reductant in the presence of potassium ferricyanide. First, NiNPs were potentiostatically electrodeposited on CC. Then, the electrodeposited NiNPs was oxidized to Ni²⁺ by GO. The produced Ni²⁺ reacted immediately with potassium ferricyanide to form nanostructured nickel hexacyanoferrate. By tuning the electrodeposition time of NiNPs, the mass of the finally produced Ni-HCF can be easily adjusted. In this work, the mass-loading of Ni-HCF supported on CC reaches up to 26.4 mg cm⁻². As the positive electrode, Ni-HCF/CC possesses a high areal capacity of 6.9 C cm⁻² at a discharge current density of 10 mA cm⁻², excellent cycling stability with 81% of its initial capacitance after 2000 continuous charge/discharge cycles, ultrahigh energy density of 36 W h kg⁻¹ at the power density of 200 W kg⁻¹ and nearly 100% columbic efficiency. The superior energy storage capability of Ni-HCF indicates its promising prospect as the positive electrode material of high performance supercapacitors.