Monodisperse hollow and core-shell magnetite (Fe₃O₄) spheres have been prepared by a simple one-pot method based on hydrothermal treatment of FeCl₃ , citrate, polyacrylamide and urea. The as-prepared samples have been characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, nitrogen adsorption-desorption isotherms, superconducting quantum interference device magnetometer. The results of control experiments reveal that citrate and polyacrylamide are crucial for the formation of spherical product and the well known Ostwald ripening process is responsible for the transformation from solid spheres to hollow and core-shell spheres. The hollow and core-shell magnetite spheres are porous and highly water soluble. They exhibit superparamagnetic properties with relatively high saturation magnetization at room temperature. The superparamagnetic properties, high magnetization, high water solubility, together with the hollow interiors will render them ideal candidates for various biomedical applications.

Recently developed solid-state catalysts can mediate carbon dioxide (CO₂) electroreduction to valuable products at high rates and selectivities. However, under commercially relevant current densities of > 200 milliamperes per square centimeter (mA cm⁻²), catalysts often undergo particle agglomeration, active-phase change, and/or element dissolution, making the long-term operational stability a considerable challenge. Here we report an indium sulfide catalyst that is stabilized by adding zinc in the structure and shows dramatically improved stability. The obtained ZnIn₂S₄ catalyst can reduce CO₂ to formate with 99.3% Faradaic efficiency at 300 mA cm⁻² over 60 h of continuous operation without decay. By contrast, similarly synthesized indium sulfide without zinc participation deteriorates quickly under the same conditions. Combining experimental and theoretical studies, we unveil that the introduction of zinc largely enhances the covalency of In-S bonds, which “locks” sulfur—a catalytic site that can activate H₂O to react with CO₂, yielding HCOO* intermediates—from being dissolved during high-rate electrolysis.

Electrochemical synthesis of valuable chemicals and feedstocks through carbon dioxide (CO ₂ ) reduction in acidic electrolytes can surmount the considerable CO ₂ loss in alkaline and neutral conditions. However, achieving high productivity, while operating steadily in acidic electrolytes, remains a big challenge owing to the severe competing hydrogen evolution reaction. Here, we show that vertically grown bismuth nanosheets on a gas-diffusion layer can create numerous cavities as electrolyte reservoirs, which confine in situ–generated hydroxide and potassium ions and limit inward proton diffusion, producing locally alkaline environments. Based on this design, we achieve formic acid Faradaic efficiency of 96.3% and partial current density of 471 mA cm ⁻² at pH 2. When operated in a slim continuous-flow electrolyzer, the system exhibits a full-cell formic acid energy efficiency of 40% and a single pass carbon efficiency of 79% and performs steadily over 50 h. We further demonstrate the production of pure formic acid aqueous solution with a concentration of 4.2 weight %.

Various CuO nanostructures have been well studied as anode materials for lithium ion batteries (LIBs); however, there are few reports on the synthesis of porous CuO nanostructures used for anode materials, especially one-dimensional (1D) porous CuO. In this work, novel 1D highly porous CuO nanorods with tunable porous size were synthesized in large-quantities by a new, friendly, but very simple approach. We found that the pore size could be controlled by adjusting the sintering temperature in the calcination process. With the rising of calcination temperature, the pore size of CuO has been tuned in the range of ∼0.4 nm to 22 nm. The porous CuO materials have been applied as anode materials in LIBs and the effects of porous size on the electrochemical properties were observed. The highly porous CuO nanorods with porous size in the range of ∼6 nm to 22 nm yielded excellent high specific capacity, good cycling stability, and high rate performance, superior to that of most reported CuO nanocomposites. The CuO material delivers a high reversible capacity of 654 mA h g⁻¹ and 93% capacity retention over 200 cycles at a rate of 0.5 C. It also exhibits excellent high rate capacity of 410 mA h g⁻¹ even at 6 C. These results suggest that the facile synthetic method of producing a tunable highly porous CuO nanostructure can realize a long cycle life with high reversible capacity, which is suitable for next-generation high-performance LIBs.