Zeolitic Imidazolate Framework-Derived Zn/Co-S@Ni(OH)2 Nanoarrays with Excellent Energy Storage and Electrocatalytic Performance

The design and development of high-performance electrochemical electrode materials are crucial for energy storage and conversion systems. This work reports a facile preparation of a self-supported Zn/Co-S@Ni(OH)2 array electrode in which a Zn/Co-S nanosheet is derived from a leaf-like zeolitic imidazolate framework (Zn/Co-ZIF-L). The core-shell structure provides multiple benefits such as enhanced electrical conductivity, an abundance of exposed active sites, and strong electronic interactions between Zn/Co-S and ultra-thin Ni(OH)2 nanosheets, facilitating faster charge transfer. Consequently, Zn/Co-S@Ni(OH)2 demonstrates remarkable electrochemical characteristics as an electrode material for supercapacitors with an area capacitance of 12.9 F cm-2 at a current density of 2 mA cm-2 in 2 M KOH. The assembled asymmetric supercapacitor device achieves a high energy density of 0.95 mW h cm-2, while showing excellent longevity with a retention of 90.9% over 5000 cycles. Additionally, the Zn/Co-S@Ni(OH)2 arrays demonstrate significant oxygen evolution reaction activity with an overpotential of 242 mV at 10 mA cm-2 in 1 M KOH and significant stability for more than 100 h. This work provides a valuable approach for synthesizing bifunctional electrode materials for both energy storage and electrocatalysis applications.

3D hierarchical ZnCo2S4@Ni(OH)2 nanowire arrays with excellent flexible energy storage and electrocatalytic performance

It is essential for energy storage and conversion systems to construct electrodes and electrocatalysts with superior performance. In this work, ZnCo₂S₄@Ni(OH)₂ nanowire arrays are synthesized on nickel foam by hydrothermal methods. As a supercapacitor electrode, the ZnCo₂S₄@Ni(OH)₂ structure exhibits a specific capacitance of 1,263.0C g^-1 at 1 A g^-1. The as-fabricated ZnCo₂S₄@Ni(OH)₂//active carbon device can achieve a maximum energy density of 115.4 Wh kg^-1 at a power density of 5,400 W kg^-1. As electrocatalysts, the ZnCo₂S₄@Ni(OH)₂ structure delivers outstanding performance for oxygen evolution reaction (an overpotential of 256.3 mV at 50 mA cm^-2), hydrogen evolution reaction (141.7 mV at 10 mA cm^-2), overall water splitting (the cell voltage of 1.53 V at 50 mA cm^-2), and a high stability for 13 h.

Microwave heating followed by a solvothermal method to synthesize nickel–cobalt selenide/rGO for high-performance supercapacitors

Efficient microwave heating followed by a solvothermal method is used to synthesize (Ni0.85Se)3(Co0.85Se)/rGO nanorods with an ultrahigh specific capacitance of 2009 F g−1 at a current density of 2 A g−1.

Synergistic effect of microwave heating and hydrothermal methods on synthesized Ni2CoS4/GO for ultrahigh capacity supercapacitors

A simple and efficient strategy that takes advantages of the synergistic effect of microwave heating method and hydrothermal method is used to synthesize Ni₂CoS₄/graphene oxide (MH-Ni₂CoS₄/GO). Firstly, Ni₂CoS₄ nanoparticles are observed to grow uniformly on the surface of GO. Then the obtained MH-Ni₂CoS₄/GO electrode is tested and it demonstrates ultrahigh specific capacitance of 2675.0 F g^-1 at the current densities of 2 A g^-1, fantastic stability of 95.0% even after 2000 cycles at 30 A g^-1 and excellent rate capability of 89.7% with current density increasing from 2 A g^-1 to 30 A g^-1. Moreover, the assembled AC//MH-Ni₂CoS₄/GO asymmetric supercapacitor also delivers a good specific capacitance of 126.5 F g^-1 at 0.5 A g^-1, outstanding stability of 97.0% after 2000 cycles at 5.0 A g^-1, and an ultrahigh energy density of 59.6 Wh kg^-1 at power density of 497.6 W kg^-1. This work provides an approach to synthesize electrode materials with superior excellent performances and it can be easily scaled up for practical applications in supercapacitors.