NiCoMo nano-alloys embedded B,N,O,F,P-rich fibrous 2D-carbon-nanoflakes/MXene nanocomposites with hierarchical structure for high performance supercapacitors

Carbon–metal nanocomposites (CMNs) with unique morphologies and chemical properties have attracted great interest in recent years for energy storage applications due to their enhanced electrical conductivity, cycling stability, specific capacitance (Cs), power density (Pd), and energy density (Ed). A simple protocol was developed to fabricate eggshell membrane (ESM)-derived electrode materials, ECNFs-HMt-G and ECNFs-HMt-Mx, resulting in a fibrous 2D carbon nanoflake-like morphology embedded with NiCoMo oxide nanoalloys and either graphene or MXene. The prepared electrode materials exhibited a hierarchical structure with a high content of heteroatom functionalities, including B, N, O, F, and P. In a three-electrode system, ECNFs-HMt-G and ECNFs-HMt-Mx delivered excellent Cs values of 1490.5 and 2307.6 F g–1, respectively, at 1 A g–1. In a two-electrode system, the corresponding Cs values were 175.8 and 235.8 F g–1, respectively, at 1 A g–1. The ECNFs-HMt-Mx also demonstrated a maximum Ed of 28.9 Wh kg⁻1 at a Pd of 5475.8 W kg–1. Excellent cycling stability of 90.5% was retained after 10,000 cycles at 1 A g⁻1, with an initial coulombic efficiency of 90.3% (84.2% after 10,000 cycles). To the best of our knowledge, this is the first ESM-derived electrode material with a fibrous 2D nanoflake-like morphology reported for energy storage applications, with performance comparable to or exceeding the most previously reported electrode materials. • Fibrous 2D-carbon-nanoflakes embedded with NiCoMo-oxide and graphene or MXene were achieved. • ECNFs-HMt-G and ECNFs-HMt-Mx exhibited Cs of 1490.5 and 2307.6 F/g, respectively. • In two electrode system, ECNFs-HMt-Mx achieved an excellent Cs of 235.8 F/g. • ECNFs-HMt-Mx reached Pd of 28.9 Wh kg−1 and Ed of 5475.8 W kg−1 with cycle stability of 90.5% after 10,000 cycles at 1 A/g. • ECNFs-HMt-Mx is robust with ICE of 90.3% after 10,000 cycles at 1 A/g. Caption: ESM-derived 2D carbon nanoflakes with NiCoMo/MXene deliver ultrahigh capacitance and durability for advanced supercapacitors. Synopsis: Eggshell membrane–derived fibrous 2D carbon nanoflake/MXene composites embedded with NiCoMo nanoalloys and enriched with multiple heteroatoms (B, N, O, F, P) were engineered. Their hierarchical nanostructure delivers outstanding capacitance, high energy/power densities, and stable cycling over 10,000 cycles. This sustainable electrode design surpasses most MXene- and biomass-based systems, setting a new benchmark for high-performance supercapacitors.