CuCo2O4 Hollow Microspheres with Graphene Composite Targeting Superior Lithium-Ion Storage

CuCo2O4/CuO Heterostructure with Oxygen Vacancies Induced by Plasma for Electrocatalytic Nitrate Reduction to Ammonia

Electrochemical nitrate reduction (NO3RR) to ammonia production is regarded as one of the potential alternatives for replacing the Haber-Bosch technology for realizing artificial ammonia synthesis. In this study, a CuCo2O4/CuO-Ar heterostructure in the shape of dandelion nanospheres formed by nanoarrays has been successfully constructed, demonstrating excellent NO3RR performance. Experimental results indicate that Ar plasma etching of CuCo2O4/CuO-Ar significantly increases the content of oxygen vacancies compared to the sample of CuCo2O4/CuO-Air etched by air plasma, resulting in improved NO3RR performance. Density functional theory calculations further confirm that the existence of more oxygen vacancies effectively decreases the energy barrier of nitrate adsorption, which is due to the generation of more oxygen vacancies facilitating nitrate adsorption and weakening the N-O bonds of nitrate after plasma treatment. As a result, CuCo2O4/CuO-Ar exhibits a high NH3 yield of 0.55 mmol h-1 cm-2 and a Faraday efficiency of 95.07% at the optimal potential of -0.9 V (vs RHE) in a neutral medium. Importantly, CuCo2O4/CuO-Ar also showcases excellent electrocatalytic stability. This study presents new views on the design and structure regulation of NO3RR electrocatalysts and their potential applications in the future.

Controllable Synthesis, Formation Process, and Luminescence Performances of Diverse Yttrium Compounds with Hollow Structures

Hollow spherical Y₂O₃ and YBO₃ have been prepared by a facile template-directed strategy using phenol-formaldehyde (PF) resin spheres as templates. The PF@Y(OH)CO₃ precursor can be fabricated by a simple precipitation route. The Y₂O₃ hollow spheres are obtained via a direct annealing process, and the hollow spherical YBO₃ are fabricated via a hydrothermal route followed by an annealing process at the expense of the same PF@Y(OH)CO₃ precursor. The whole synthesis procedure is performed in aqueous solution without any surfactant or catalyst. Moreover, YVO₄ quasi-octahedral microcrystals with spherical holes are obtained. The formation mechanisms of the yttrium compounds with different morphologies have been discussed. By incorporating proper rare earth activator ions into the Y₂O₃, YBO₃, and YVO₄ hosts, the as-synthesized luminescent materials can exhibit eminent performances with both down-conversion and up-conversion luminescence. Furthermore, the as-fabricated light-emitting diode (LED) devices can emit dazzling characteristic emission light, which reveals that the phosphors have application potential in lighting and displays. This simple synthesis strategy may provide a new idea for the fabrication of inorganic compounds with perfect hollow structures and excellent properties.

Synthesis of MnO-Sn cubes embedding in nitrogen-doped carbon nanofibers with high lithium-ion storage performance

In this paper, a carbon nanofiber (CNF) hybrid nanomaterial composed of MnO-Sn cubes embedding in nitrogen-doped CNF (MnO-Sn@CNF) is synthesized through electrospinning and post-thermal reduction processes. It exhibits good electrochemical lithium-ion storage performance as the anode, such as high reversible capacity, outstanding cycle performance (754 mAh g^-1at 1 A g^-1after 1000 cycles), and good rate capability (447 mAh g^-1at 5 A g^-1). The excellent electrochemical properties are derived from a unique nanostructure design. MnO-Sn@CNF has a three-dimensional conductive network with a stable core-shell structure, which improves the electrical conductivity and mechanical stability of the materials. In addition, the mesopores on the surface of carbon fibers can shorten the diffusion distance of lithium ions and promote the combination of active sites of the material with lithium ions. The internal MnO and Sn form a heterostructure, which enhances the stability of the physical structure of the electrode material. This material design method provides a reference strategy for the development of high-performance lithium-ion batteries anode.