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Two-dimensional (2D) multilayered graphitic carbon nanosheets are prepared via a facile, green, and mild method of one-pot hydrothermal carbonization at a temperature below 300 °C. Copper with a 2D structure is formed in situ and serves as both a template and catalyst. The obtained multilayered carbon nanosheets exhibit well-defined shapes and a radius-to-thickness ratio as high as 104, with monolayer thickness as small as 2.86 nm. [ABSTRACT FROM AUTHOR]

The development of flexible three-dimensional (3D) nanostructured electrodes has been regarded as a promising strategy to fulfill high-performance supercapacitors. Herein, we report a cost-effective method for fabricating flexible supercapacitor electrodes consisting of NiCo-LDH nanosheets electrodeposited on 3D porous Ni arrays/conductive cloth (NiCo-LDH@3D Ni/CC). The hierarchical 3D porous Ni arrays with high conductivity and large specific area not only provide effective interconnected conductive networks, but also enable a high mass loading of active materials. The resultant NiCo-LDH@3D Ni/CC electrode exhibits a high mass capacitance of 2248 F g−1 and a high areal capacitance of 3260 mF cm−2 at 5 mA cm−2. Ultimately, the symmetric solid-state supercapacitor assembled with NiCo-LDH@3D Ni/CC displays a high areal capacitance of 116.7 mF cm−2 at 5 mA cm−2, and excellent cycling stability (full capacitance retention after 10,000 cycles at 10 mA cm−2). This work demonstrates a facile and low-cost strategy for flexible energy storage applications. [ABSTRACT FROM AUTHOR]

Developing highly efficient and low-cost oxygen evolution reaction (OER) electrocatalysts is highly demanded, as the OER is recognized as a key half-reaction in water splitting for producing hydrogen; however, this still remains a great challenge. Herein, we design three-dimensional (3D) tubular hierarchical core–shell electrocatalysts for the OER using a simple and highly controllable two-step method. The large-scale tubular Cu(OH)2 arrays are directly grown on Cu foam (CF) at room temperature, followed by the growth of highly porous CoNi carbonate hydroxides (CH) via a low-temperature hydrothermal method on the walls of these Cu(OH)2 nanotubes (NTs). The hollow and open-structured core–shell hierarchical Cu(OH)2@CoNiCH NTs/CF electrode with a large surface area and numerous mesoporous and short diffusion paths can provide many active sites, fast electron transport and easy accessibility of water, leading to an excellent OER activity in an alkaline electrolyte with an overpotential of 288 mV and 326 mV at a current density of 30 mA cm−2 and 100 mA cm−2, respectively, also with robust durability. This new structure would open an avenue for the advancement of highly efficient OER electrocatalysts. [ABSTRACT FROM AUTHOR]

Flowerlike NiCo 2 S 4 hollow sub-microspheres are synthesized through Cu 2 O templates to support Pd nanoparticles as high-efficiency catalysts for the hydrogen evolution reaction (HER). The diameter and shell size of NiCo 2 S 4 hollow sub-microspheres are about 400 and 16 nm, respectively. In addition, the surface of the shells is constructed by petallike nanosheets. About 3 nm Pd particles uniformly incorporate with the flowerlike NiCo 2 S 4 hollow sub-microsphere to form the NiCo 2 S 4 /Pd heterostructure. The NiCo 2 S 4 /Pd catalysts exhibit significantly lower overpotential of only 87 and 83 mV at 10 mA/cm 2 for the HER in both acidic and alkaline conditions, respectively, relative to NiCo 2 S 4 (247, 226 mV) and Pd (175, 385 mV) catalysts. Besides, the NiCo 2 S 4 /Pd catalysts also exhibit excellent stability of HER in these two conditions. The superior HER performance of NiCo 2 S 4 /Pd might be resulted from the unique architecture of metal nanoparticles anchored on the bimetallic sulfide flowerlike hollow sub-microspheres, which could provide high surface area, lots of active sites, strong synergetic effect, and stable structure.