In this work, Ni3S2/Ni foam was successfully synthesized using a facile gas-phase method of annealing Ni foam in H2S atmosphere. It was used as a binder free electrode for high-performance supercapacitors. The areal capacitance increases rapidly in the initial charge-discharge cycling and then reaches a stable stage. An ultrahigh areal capacitance of 9.88 F cm(-2) at the current density of 10 mAcm(-2) is achieved in the stable charge-discharge stage, which is around 88 times of initial capacitance (112.5 mF cm(-2)). Further studies reveal that surface Ni3S2 transforms into porous Ni(OH) 2 during charge-discharge process, and surface area increases more than 100 times. The soaring specific surface area is the dominant factor contributing to the increased areal capacitance. More importantly, this self-formed porous structure exhibits ultra-stable long-time cycling ability, as no capacity fading is observed even after 60000 cycles of charge-discharge at high current density (150 mAcm(-2)). These results indicate that selfformed porous Ni(OH)(2) structure during electrochemical cycling maybe a promising electrode for high performance supercapacitor applications. (c) 2019 Elsevier Ltd. All rights reserved.