Deep eutectic solvent assisted facile synthesis of low-dimensional hierarchical porous high-entropy oxides

High-entropy-oxides (HEOs), a new class of solids that contain five or more elemental species, have attracted increasing interests owing to their unique structures and fascinating physicochemical properties. However, it is a huge challenge to construct various nanostructured, especially low-dimensional nanostructured HEOs under the high temperature synthetic conditions. Herein, a facile strategy using glucose-urea deep eutectic solvent (DES) as both a solvent and the carbon source of structure-directed template is proposed for the synthesis of various HEOs with two-dimentional (2D) nanonets and one-dimentional (1D) nanowires, including rock-salt (Co, Cu, Mg, Ni, Zn)O, spinel (Co, Cr, Fe, Mn, Ni)(3)O-4, and perovskite La(Co, Cr, Fe, Mn, Ni)O-3. The as-prepared HEOs possessed five or more uniformly dispersed metal elements, large specific surface areas (more than 25 m(2)center dot g(-1)), and a pure single-phase structure. In addition, high cooling rate (cooling in air or liq-N-2-quenching) was indispensable to obtain a single-phase rock-salt (Co, Cu, Mg, Ni, Zn)O because of phase separation caused by copper. By taking advantage of unique features of HEOs, rock-salt (Co, Cu, Mg, Ni, Zn)O can function as a promising candidate for lithium-ion batteries (LIBs) anode material, which achieved excellent cycling stability. This work provides a feasible synthetic strategy for low-dimensional hierarchical HEOs, which creates new opportunities for the stable HEOs being highly active functional materials.

Automated summary

High-entropy-oxides (HEOs) have unique structures and fascinating physicochemical properties, but constructing various nanostructured HEOs under high temperature synthetic conditions is challenging. A strategy using deep eutectic solvent (DES) as a solvent and carbon source was proposed, successfully synthesizing HEOs with 2D nanonets and 1D nanowires. These HEOs have uniformly dispersed metal elements, large specific surface areas, and a pure single-phase structure, providing new opportunities for stable HEOs as highly active functional materials.