MOF-derived spherical Ni S /carbon with B-doping enabling high supercapacitive performance

This work uses a simple Ni-metal organic framework (Ni-MOF) to generate a uniform metal-containing carbon hybrid structure of Ni/C by in-situ pyrolysis. Then, after NaBH4 treatment and hydrothermal vulcanization of Ni/C, multiphase B-doped NixSy nanoparticles can be obtained and uniformly anchored in the carbon skeleton, forming a highly porous flower-shaped B-NixSy/C composite. The positive role of B doping was theoretically confirmed by Density Function Theory (DFT) calculations. The MOF-derived carbon framework has porous, conductive, and continuous features beneficial for fast charge transfer. There are also multiple Ni-sulfide phases in B-NixSy/C, dominated by hexagonal NiS, hexagonal Ni2S3, and cubic Ni3S4, which give rich valance state and are expected to bring active electrochemical reactions. In addition, the boronation process by the reducing agent of NaBH4 is also proved beneficial to bring high capacitance, possibly due to the incorporation of more active sites by B. Therefore, the B-NixSy/C composite electrode delivers a high specific capacity of 1250.4 C g–1 at 1 A g–1 and excellent rate performance. The B-NixSy/C-based asymmetric supercapacitor also shows promising prospects for future energy storage devices, delivering high cyclability with capacitance retention of 87.6% after 7000 cycles. This work proves the efficiency of MOF-derived carbon framework and B-doping in improving metal sulfide's electrochemical performances.