Insight on electrochemical charge storage behavior of naturally surface oxidized amorphous NiCuCoB nanosheets

Transition metal boron (TMB) nanostructures are found to be emerging materials in the field of energy conversion and storage. Despite several careful systematic researches on the TMBs and their electrochemical energy storage applications, still a comprehensive and insightful study on the charge storage mechanism, origin of the redox reaction sites on alloyed TMB surface, types of interactions of the electrolytes with respect to TMB's surface structure has not been realized. Herein, a series of TMBs nanosheets are prepared using Cu, Co, Ni and B through a simple low-cost reduction approach and explored systematically their charge storage behavior. Trimetallic NiCuCoB nanosheets over other TMBs demonstrated outstanding electrochemical energy storage performances with high-rate capability. A symmetric two-electrode coin cell device of NiCuCoB in 6.0 M KOH offers 358 F g-1 specific capacitance with 56 Wh kg-1 energy and 13,320 W kg-1 power density, with 50,000 cycling stability. Kinetically fluent faradaic redox reactions are favourably occurred by a surface-controlled mechanism with minor contribution from diffusion, which are facilitated by oxidized surface of NiCuCoB viz., metal-oxide and/or metal-oxy/hydroxide, a high surface area and high conductivity of the material, as evidenced by experiments.