Influence of Pre-Adsorbed TiO₂ Particles on the Nucleation and Growth Mechanism of Ni in Deep Eutectic Solvent Electro-Codeposition

Electrodeposition holds excellent potential for creating controllable nanoscale functional interfaces. However, the key characteristics of these processes remain elusive, especially the composite electrodeposition processes involving inert nanoparticles. Herein, the pre-adsorption of inert particles is considered in detail in electro-codeposition. The nucleation and growth mechanism of nickel nanoparticles under the influence of pre-adsorbed inert particles is studied in a choline chloride–ethylene glycol deep eutectic solvent (DES). Cyclic voltammetry results show that pre-adsorbed TiO2 particles can significantly increase the cathodic reduction current, while codeposited TiO2 particles hinder the reduction process. Chronoamperometry analysis demonstrates that pure Ni electrodeposition in a DES follows the mechanism of instantaneous nucleation and tridimensional growth at a high potential, while the Ni electrodeposition deviated from the instantaneous nucleation model due to the pre-adsorption of TiO2 particles. Moreover, considering the classical model description of multiphase 3D nucleation and diffusion-controlled growth, the typical kinetic parameters such as nucleation rate constant and diffusion coefficient were investigated under different applied potentials. It was found that the nucleation rate constant of Ni electrodeposition increased significantly in the presence of pre-adsorbed TiO2 particles. These findings are of great significance for understanding and perfecting the electro-codeposition process containing inert nanoparticles

Hollow Mesoporous Co(PO₃)₂@Carbon Polyhedra as High Performance Anode Materials for Lithium Ion Batteries

The hollow mesoporous Co­(PO3)2@carbon nanocomposite (H–Co­(PO3)2@C) was synthesized using ZIF-67 as the template by a facile one-step thermal decomposition reaction. As an anode for lithium ion batteries, its reversible capacity remains up to 601 mAh g–1 at 1 C after 500 cycles. Such a high reversible capacity along with the excellent rate capability and long-term cycling stability benefits from the hollow mesoporous structure and uniform carbon framework encapsulated active nanocrystals. These results render the as-prepared H–Co­(PO3)2@C to be a promising anode material for high performance lithium ion batteries

Highly Strained Au Nanoparticles for Improved Electrocatalysis of Ethanol Oxidation Reaction

Au is an ideal noble metal for use as an electrocatalyst for the ethanol oxidation reaction owing to its high performance-to-cost ratio. The catalyst usually exists as nanoparticles (NPs) for high surface area-to-volume ratio. In the present work, a nontraditional physical approach has been developed to fabricate ultrasmall and homogeneous single-crystalline Au NPs by ion bombardment in a precision ion polishing system. Transmission electron microscopy characterizations show that the Au NPs produced with 5 keV Ar+ are highly strained to form twinned crystals, which accumulate a large amount of surface energy, and this was found to be an underlying reason causing strong catalysis. Electrochemistry tests reveal that in alkaline medium the C1 pathway occurs much more preferentially with the strained Au NPs than the normal Au NPs. The surface area-to-volume ratio is no longer the only factor that affects the performance; instead, surface energy might play a more important role in enhancing the catalytic activities

Nanostructured CuO/C Hollow Shell@3D Copper Dendrites as a Highly Efficient Electrocatalyst for Oxygen Evolution Reaction

Adoption of bare metal oxides as catalytic materials shows inferior electrochemical activity because of their poor electrical conductivity. Although synthetic strategies for the employment of conductive substrates are well-established, the rational design and fabrication of hollow metal oxides nanostructures on the robust matrix with a high surface area and conductivity remains challenging. In the present research work, a strategy that transforms a metal–organic framework thin layer into a nanostructured CuO/C hollow shell to coat on the 3D nano-dendritic Cu foams as an electrode was successfully developed. This electrode is claimed to provide an extraordinary electrocatalysis for oxygen evolution reaction (OER) in alkaline media. The hierarchical complex presents fast electronic transmission networks and rich redox sites, leading to the significant enhancement in electrocatalytic OER efficiency. Furthermore, the spherical porous structure and robust architecture facilitate the high-speed diffusion of O₂ bubbles in a long-term operation. The results of this study may serve as a reference for the designing of novel class 3D metal/metal oxide hierarchical structures for gas-involved (i.e., O₂, H₂, and CO₂) electrocatalytic applications and beyond

Efficient Spin–Orbit Torque Switching in a Perpendicularly Magnetized Heusler Alloy MnPtGe Single Layer

Electrically manipulating magnetic moments by spin–orbit torque (SOT) has great potential applications in magnetic memories and logic devices. Although there have been rich SOT studies on magnetic heterostructures, low interfacial thermal stability and high switching current density still remain an issue. Here, highly textured, polycrystalline Heusler alloy MnxPtyGe (MPG) films with various thicknesses are directly deposited onto thermally oxidized silicon wafers. The perpendicular magnetization of the MPG single layer can be reversibly switched by electrical current pulses with a magnitude as low as 4.1 × 1010Am–2, as evidenced by both the electrical transport and the magnetic optical measurements. The switching is shown to arise from inversion symmetry breaking due to the vertical composition gradient of the films after sample annealing. The SOT effective fields of the samples are analyzed systematically. It is found that the SOT efficiency increases with the film thickness, suggesting a robust bulk-like behavior in the single magnetic layer. Furthermore, a memristive characteristic has been observed due to a multidomain switching property in the single-layer MPG device. Additionally, deterministic field-free switching of magnetization is observed when the electric current flows orthogonal to the direction of the in-plane compositional gradient due to the in-plane symmetry breaking. This work proves that the MPG is a good candidate to be utilized in high-density and efficient magnetoresistive random access memory devices and other spintronic applications