Generalized Low-Temperature Fabrication of Scalable Multi-Type Two-Dimensional Nanosheets with a Green Soft Template

α- and β-Phase Ni-Mg Hydroxide for High Performance Hybrid Supercapacitors

Mg-substituted α- and β-phase nickel hydroxides with high specific capacitance and good stability have been synthesized via sacrificial metal-based replacement reaction. 2D α- and β-phase nickel-magnesium hydroxide (NiMg-OH) have been synthesized by sacrificing magnesium (Mg) powder with nickel salt aqueous solutions. Interestingly, the phase of the obtained NiMg-OH can be controlled by adjusting the nickel precursor. As well, the Mg powder is used not only as Mg source but also alkali source to form NiMg-OH. The α-phase nickel-magnesium hydroxide sample (α-NiMg-OH) exhibits lager surface area of 290.88 m² g^–1. The electrochemical performances show that the α-NiMg-OH presented a superior specific capacitance of 2602 F g^–1 (1 A g^–1) and β-phase nickel-magnesium hydroxide sample (β-NiMg-OH) exhibits better stability with 87% retention after 1000 cycles at 10 A g^–1. The hybrid supercapacitor composed of α-NiMg-OH and activated carbon (AC) display high storage performance and cycle stability, it presents 89.7 F g^–1 (1 A g^–1) and of 0–1.6 V potential window and it maintains capacitance retention of 84.6% subsequent to 4000 cycles.

A general strategy for facile synthesis of ultrathin transition metal hydroxide nanosheets

A general strategy to produce 2D transition metal hydroxide nanosheets is proposed here. This 'green chemistry' approach requires less equipment, includes simple operation steps and costs little. FeOOH, Co(OH)2, Ni(OH)2, Fe-Mn hydroxide, Co-Zn hydroxide and Ni-Zn hydroxide nanosheets were successfully synthesized through a mechanism of preferentially oriented growth. The produced nanosheets are ultrathin and possess large specific surface area. The representative unmodified FeOOH nanosheets exhibit potential performance for application as a positive contrast agent.

Enhanced Schottky effect of a 2D-2D CoP/g-C3N4 interface for boosting photocatalytic H2 evolution

As emerging noble metal-free co-catalysts, transition metal phosphides have been employed to improve photocatalytic H2 production activity. Herein, the metallicity of CoP, as a representative phosphide, and the Schottky effect between CoP and g-C3N4 are confirmed via theoretical calculations. Then, a 2D/2D structure is designed to enlarge the Schottky effect between the interfaces, for which the apparent quantum efficiency of the photocatalytic H2 evolution is 2.1 times that of corresponding 0D/2D heterojunctions. The morphology, microstructure, chemical composition, and physical nature of pristine CoP, g-C3N4, and the composites are characterized in order to investigate the dynamic behavior of photo-induced charge carriers between CoP and g-C3N4. Based on the measurements, it is proposed that the efficient electron collecting effect of CoP can be attributed to the superior interfacial contact and Schottky junction between the CoP and g-C3N4 interfaces. Furthermore, the excellent electrical conductivity and low overpotential of CoP make water reduction easier. This work demonstrates that the construction of a 2D/2D structure based on a suitable Fermi level is crucial for enhancing the Schottky effect of transition metal phosphides.

Hybrid α-Fe2O3@Ni(OH)2 nanosheet composite for high-rate-performance supercapacitor electrode

In this study, we report a facile fabrication of ultrathin two-dimensional (2D) nanosheet hybrid composite, α-Fe₂O₃ nanosheet@Ni(OH)₂ nanosheet, by a two-step hydrothermal method to achieve high specific capacitance and good stability performance at high charging/discharging rates when serving as electrode material of supercapacitors. The α-Fe₂O₃@Ni(OH)₂ hybrid electrode not only has a smooth decrease of the specific capacitance with increasing current density, compared with the sharp decline of single component of Ni(OH)₂ electrode, but also presents excellent rate capability with a specific capacitance of 356 F/g at a current density of 16 A/g and excellent cycling stability (a capacity retention of 93.3% after 500 cycles), which are superior to the performances of Ni(OH)₂ with a lower specific capacitance of 132 F/g and a lower capacity retention of 81.8% at 16 A/g. The results indicate such hybrid structure would be promising as excellent electrode material for good performances at high current densities in the future.