Integrated carbon nanosheet frameworks inlaid with nickel phosphide nanoparticles by substrate-free chemical blowing and phosphorization for aqueous asymmetric supercapacitor

Herein, a nickel nitrate-assisted polymer (gelatin), in situ substrate-free chemical blowing pyrolysis and subsequent low-temperature phosphorization method are used to prepare nickel phosphide nanoparticle self-inlaid carbon nanosheet frameworks (Ni2P-CNFs). The presence of CNFs in the Ni2P-CNFs structure can not only provide fast electrically conductive channels but also prevents the aggregation of the Ni2P nanoparticles, which results in maximum utilization of the reactive sites. Therefore, the as-fabricated Ni2P-CNFs used as a positive electrode for the supercapacitor shows a high specific capacity of 145 mAh g(-1) at a current density of 0.5 A g(-1), an excellent rate capability with 70% capacity retention as the current density increases in 20 times. To highlight, a novel aqueous asymmetric supercapacitor based on a positive Ni2P-CNFs electrode and a negative CNFs electrode is assembled, achieving a large operating voltage of 1.65 V, high energy density of 42 Wh kg(-1) at a power density of 413 W kg(-1), and outstanding cycling stability with 88% capacity retention after 6000 cycles. This study provides a top-down strategy for designing integrated and robust metallic self-decorated porous carbon nanomaterials, which may inspire further development for electrochemical energy storage and conversion applications. (C) 2019 Elsevier B.V. All rights reserved.