Core-shell CoMoO4@Ni(OH)2 on ordered macro-porous electrode plate for high-performance supercapacitor

Enhanced performance of hybrid supercapacitors by the synergistic effect of Co(OH)2 nanosheets and NiMn layered hydroxides

A self-supporting composite electrode material with a unique three-dimensional structure was synthesized by in-situ growth of nanoscale NiMnLDH-Co(OH)₂ on a nickel foam substrate via hydrothermal electrodeposition. The 3D layer of NiMnLDH-Co(OH)₂ provided abundant reactive sites for electrochemical reactions, ensuring a solid and conductive skeleton for charge transfer and resulting in significant enhancement of electrochemical performance. The composite material showed a strong synergistic effect between the small nano-sheet Co(OH)₂ and NiMnLDH, which promoted reaction kinetics, while the nickel foam substrate acted as a structural conductivity agent, stabilizer, and good conductive medium. The composite electrode showed impressive electrochemical performance, achieving a specific capacitance of 1870F g^-1 at 1 A g^-1 and retaining 87% capacitance after 3000 charge-discharge cycles, even at a high current density of 10 A g^-1. Moreover, the resulting NiMnLDH-Co(OH)₂//AC asymmetric supercapacitor (ASC) demonstrated remarkable specific energy of 58.2 Wh kg^-1 at a specific power of 1200 W kg^-1, along with outstanding cycle stability (89% capacitance retention after 5000 cycles at 10 A g^-1). More importantly, DFT calculations reveal that NiMnLDH-Co(OH)₂ facilitates charge transfer, accelerating surface redox reactions and increasing specific capacitance. This study presents a promising approach towards designing and developing advanced electrode materials for high-performance supercapacitors.

Hierarchical CuCo2O4@CoS-Cu/Co-MOF core-shell nanoflower derived from copper/cobalt bimetallic metal-organic frameworks for supercapacitors

Rational design of composite materials with unique core-shell nanoflower structures is an important strategy for improving the electrochemical properties of supercapacitors such as capacitance and cycle stability. Herein, a two-step electrodeposition technique is used to orderly synthesize CuCo₂O₄ and CoS on Ni foam coated with Cu/Co bimetal metal organic framework (Cu/Co-MOF) to fabricate a hierarchical core-shell nanoflower material (CuCo₂O₄@CoS-Cu/Co-MOF). This unique structure can increase the electrochemically active site of the composite, promoting the Faradaic redox reaction and enhancing its electrochemical properties. CuCo₂O₄@CoS-Cu/Co-MOF shows a prominent specific capacitance of 3150 F g^-1 at 1 A g^-1, marvelous rate performance of 81.82% (2577.3 F g^-1 at 30 A g^-1) and long cycle life (maintaining 96.74% after 10,000 cycles). What is more, the assembled CuCo₂O₄@CoS-Cu/Co-MOF//CNTs device has an energy density of 73.19 Wh kg^-1 when the power density is 849.94 W kg^-1. It has unexpected application prospects.

Formation of V6O11@Ni(OH)2/NiOOH hollow double-shell nanoflowers for the excellent cycle stability of supercapacitors

The rational design of multi-shelled hollow structured electrode materials is of great importance and has met with fundamental challenges in recent years. Herein, we demonstrate a combination approach of self-templating and sacrificial templating method for synthesizing double-shelled hollow nanoflower-structured V₆O₁₁@Ni(OH)₂/NiOOH. Firstly, highly uniform vanadium-glycerate (VG) solid nanospheres are controllably synthesized and employed as the template, then Ni(OH)₂/NiOOH nanosheets grow vertically on it, following with VG solid nanospheres changing to the V₆O₁₁ hollow structure. By controlling the amount of Ni(OH)₂/NiOOH nanosheets, the optimized V₆O₁₁@Ni(OH)₂/NiOOH-6 (VN-6) delivers high performance for supercapacitors. Specifically, the specific capacitance of VN-6 is 1018.2 F g^-1 at the current density of 1 A g^-1 and the energy density is 24.3 W h kg^-1 at the power density of 850 W kg^-1. Impressively, an outstanding cycling stability of over 120% specific capacitance retention can be obtained after 5000 cycles in the three-electrode and two-electrode systems. The excellent performance can be ascribed to the compositional and structural advantages.

NiFeP nanoflakes composite with CoP on carbon cloth as flexible and durable electrocatalyst for efficient overall water splitting

High-performance and earth-abundant NiFeP is an excellent bifunctional catalyst for water splitting in acidic and alkaline environments, and NiFeP nanoflakes on CoP layer composite with a conductive carbon cloth (CC) substrate as the trunk-leaf flexible structure (NiFeP/CoP/CC) is prepared by direct high-temperature phosphorization. Overpotentials of only 96.38 and 78.80 mV are required in hydrogen evolution reaction in 1 M KOH and 0.5 M H₂SO₄, respectively, to generate an electrocatalytic current density of 10 mA cm^-2. A small Tafel slope of 70.67 and 63.21 mV per decade are also observed from NiFeP/CoP/CC revealing a Volmer-Heyrovsky mechanism in both media. The electrocatalyst also delivers excellent oxygen evolution reaction performance in the alkaline environment and long-term electrochemical durability for at least 24 h in electrolytes over a wide pH range. A device is assembled with two identical flexible ultrathin NiFeP/CoP/CC as both the anode and cathode in 1 M KOH driven by a set of 1.6 V solar cells. During 32 h of electrolysis, the results show that the current of our electrodes maintains 80% performance at a constant voltage of 1.7 V for 32 h, and the NiFeP/CoP/CC anodes and cathodes have large potential in industrial alkaline water splitting.

Hierarchical urchin-like Co9S8@Ni(OH)2 heterostructures with superior electrochemical performance for hybrid supercapacitors

The hierarchical core–shell heterostructure of Co₉S₈@Ni(OH)₂ with high open channels enables rapid electrolyte diffusion, thus enhancing the electrochemical performance.