Sodium‐Salt‐Promoted Growth of Self‐Supported Copper Oxides with Comparative Supercapacitive Properties

Abstract

In this work, we developed a facile hydrothermal system to synthesize self‐supported copper oxides with different nanostructures. In this system, we used copper foam as both the substrate and the copper source, and selected a wide range of sodium salts to serve as directing agents, promoting the formation of copper oxide with different nanostructures. We first show that, at 30 mM of sodium fluoride, we can successfully grow nanocubes on the copper foam substrate that comprise both CuO and Cu2O. Such a mixed composition is unique among the investigated salts. However, if a lower concentration of NaF or a different salt is used, Cu2O nanocrystals of different structures, such as nanoplatelets or irregular particles, can be obtained. When these samples were tested in supercapacitors, they demonstrated contrasting pseudocapacitive properties where the initial mixed Cu2O/CuO nanocube sample demonstrated a very stable reversible capacitance of about 400 mF cm−2 for 1600 cycles. This is significantly higher than that for the other samples, as well as advantageous compared to other copper‐oxide‐based electrode materials. The impedance analysis suggested that such a performance could be attributed to the low diffusion resistance of this sample.

Enhancing the Low/Middle‐Frequency Electromagnetic Wave Absorption of Metal Sulfides through F− Regulation Engineering

“…[ 5,47 ] (III)Taking advantage of the fluorine‐stabilization effect of F − on certain crystal facets also could lead to exceptional growth orientation. [ 8,48 ] Consequently, under an appropriate F − concentration during a certain reaction period, a preferred growth process could occur, inducing in situ growth of needle‐like morphology instead of microspheres‐like NiCo 2 S 4 /Co 1− x S composites, as illustrated in Figure S6, Supporting Information.…”

SeC Bonding Promoting Fast and Durable Na+ Storage in Yolk–Shell SnSe2@SeC

“…[ 18,39 ] This phenomenon is usually attributed to the electrochemical activation of the active material. [ 16 ] As pointed out earlier, [ 40 ] the insertion and deinsertion of the Na + ions into and from the interlayer spacing of layered SnSe 2 would lead to the reorganization of the microstructure in the material, creating more diffusion pathways as well as more accessible active sites. This may offer a better utilization of the active material, and thus an increase in the reversible capacity.…”

Self‐Supported Transition Metal‐Based Nanoarrays for Efficient Energy Storage

“…Chen et al. previously discovered that copper oxides could be produced by treating Cu foam hydrothermally in an aqueous solution containing sodium salts, and different anion present in the salt would lead to different morphologies of products [106] . Such a phenomenon is not observed in the Ni counterpart, suggesting that Cu might be more chemical active under such conditions.…”