Nitridation-induced in situ coupling of Ni-Co₄N particles in nitrogen-doped carbon nanosheets for hybrid supercapacitors

The self-supported integrated structure of electrode consisting of heteroatoms is advantageous for high-performance energy storage applications. Herein, we developed heteroatomic Ni-Co₄N nanoparticles laminated on highly conductive nitrogen-doped carbon (NC) matrix through in-situ nitridation for high energy and stable hybrid supercapacitor (HSC). The plenty of rendering electrochemically active sites, specifically, single-atom Ni, Co₄N nanoparticles, and heteroatomic N-doped carbon matrix, and their several synergistic effects facilitate fast electron transfer and superior electrochemical performance. Benefiting from these merits, the resultant Ni-Co₄N@NC electrode demonstrates robust electrochemical activity with high specific capacity of 397.5 mA h g⁻¹, high rate capability of 72.4% and superior cycling stability over 10,000 cycles. The heteroatomic Ni-Co₄N@NC electrode is further employed for the HSC cell beside with the activated carbon (AC) electrode, which establish the specific energy of 57.2 Wh kg⁻¹ at a specific power of 843.8 W kg⁻¹ and cyclic stability of 89.7% after 15,000 cycles. The present study highlights the utilization of heteroatomic self-supported metal nitrides for the high energy HSCs cell, paving the way to the expansion of highly efficient electrode materials for the future energy storage systems.