MOF-derived spherical Ni_(x)S_(y)/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 NaBH_(4) treatment and hydrothermal vul-canization of Ni/C,multiphase B-doped Ni_(x)S_(y) nanoparticles can be obtained and uniformly anchored in the carbon skeleton,forming a highly porous flower-shaped B-Ni_(x)S_(y)/C composite.The positive role of B doping was theoretically confirmed by Density Function Theory(DFT)calculations.The MOF-derived car-bon framework has porous,conductive,and continuous features beneficial for fast charge transfer.There are also multiple Ni-sulfide phases in B-Ni_(x)S_(y)/C,dominated by hexagonal NiS,hexagonal Ni 2 S 3,and cu-bic Ni_(3)S_(4),which give rich valance state and are expected to bring active electrochemical reactions.In addition,the boronation process by the reducing agent of NaBH_(4) is also proved beneficial to bring high capacitance,possibly due to the incorporation of more active sites by B.Therefore,the B-Ni_(x)S_(y)/C compos-ite electrode delivers a high specific capacity of 1250.4 C g^(-1) at 1 A g^(-1) and excellent rate performance.The B-Ni_(x)S_(y)/C-based asymmetric supercapacitor also shows promising prospects for future energy stor-age 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.