In-situ electrodeposited Co_0.85Se@Ni₃S₂ heterojunction with enhanced performance for supercapacitors

Rational design of porous heterostructured electrode materials for high-performance supercapacitors remains a big challenge. Herein, we report the in situ synthesis of Co_0.85Se@Ni₃S₂ hybrid nanosheet arrays supported on carbon cloth (CC) substrate though an efficient two-step electrodeposition method. Compared with pure Co_0.85Se and Ni₃S₂, the well-defined Co_0.85Se@Ni₃S₂ heterojunction possesses enriched active sites, improved electrical conductivity, and reduced ion diffusion resistance. Benefiting from its hierarchically porous nanostructure and the synergistic effect of Co_0.85Se and Ni₃S₂, the as-synthesized Co_0.85Se@Ni₃S₂ electrode delivers a gravimetric capacitance (C_g)/volumetric capacitance (C_v) of 1644.1F g^-1/3161.7F cm^-3 at 1 A g^-1, outstanding rate capability of 60.7% capacitance retention at 20 A g^-1, as well as good cycling performance of 87.8% capacitance retention after 5000 cycles. Additionally, a hybrid supercapacitor (HSC) device presents a maximum energy density (E) of 65.7 Wh kg^-1 at 696.2 W kg^-1 with 93.3% cyclic durability after 15,000 cycles. Thus, this work proposes a simple and effective strategy to fabricate porous heterojunctions as high-performance electrode materials for energy storage devices.