Multi-geometric carbon encapsulated SnP3 composite for superior lithium/potassium ion batteries.

Tin phosphide has gained extensive attention as a prospective anode for lithium/potassium ion batteries because of its high theoretical capacity. Nevertheless, the fast capacity fading, which is induced by the huge volume expansion and poor electrical conductivity during cycling, severely restricts its practical applications. In this work, a SnP3-CNTs/KB composite with a SnP3 content as high as 90 wt% was successfully synthesized by a two-step ball milling method. SnP3 nanoparticles were tightly encapsulated in multi-geometric composite carbon layers to efficiently relieve the volume changes and enhance conductivity. Specifically, the resulting SnP3-CNTs/KB anode showed a specific capacity up to 998.6 mA h g-1 after 100 cycles at 50 mA g-1 and 810.4 mA h g-1 after 500 cycles at 1000 mA g-1 for lithium ion batteries. For potassium ion batteries, a high reversible capacity of 200.2 mA h g-1 was achieved after 200 cycles at 1000 mA g-1. This work affords a new insight for exploring excellent support structures of tin phosphide-based anodes.

Coordinated d-p hybridized hcp@fcc NiRu alloy doped by interstitial atoms for boosting urea-assisted simulated seawater electrolysis at industrial current densities.

The production of hydrogen through seawater electrolysis has recently garnered increasing concern. However, hydrogen evolution reaction (HER) by alkaline seawater electrocatalysis is severely impeded by the slow H2O adsorption and H* binding kinetics at industrial current densities. Herein, a face-centered cubic/hexagonal close packed (fcc/hcp) NiRu alloy heterojunction was fabricated on Ni foam (N doped NiRu-inf/NF) by a low-temperature nitrogen plasma activation. Simultaneously, nitrogen atoms are introduced into the alloy to facilitate d-p hybridization. When N doped NiRu-inf/NF is integrated into a dual-electrode cell for urea-assisted seawater electrolysis, it achieves 100 mA cm-2 with an ultra-low voltage of 1.36 V and excellent stability. Density functional theory (DFT) verifies that the robust d-p hybridization among Ni, Ru and N exhibits more energy level matching for H2O molecule adsorption at the Ru sites, while simultaneously reducing the interaction between H* and Ni sites in N-doped NiRu-inf.

Ultrathin Metal-Organic Framework Nanosheet-Derived Ultrathin Co3O4 Nanomeshes with Robust Oxygen-Evolving Performance and Asymmetric Supercapacitors.

Ultrathin metal-organic framework (MOF) nanosheets possessing inherent advantages of both two-dimensional (2D) features and MOFs are attracting intensive research interest. The direct manufacture of MOF nanosheets is still a challenge up to now. Here, we have developed a novel bottom-up approach to synthesize zeolitic imidazolate framework-67 (ZIF-67) nanosheets, which can be in situ converted into Co3O4 ultrathin nanomeshes after thermal treatment. Interestingly, the obtained Co3O4 nanomeshes are rich in oxygen defects, providing fruitful active sites for the faradaic reaction. The modified electrode exhibits a large specific capacitance (1216.4 F g-1 at 1 A g-1), as well as a high rate capability (925.5 F g-1 at 20 A g-1). Moreover, an asymmetric supercapacitor made of Co3O4//activated carbon shows an energy density of 46.5 Wh kg-1 at 790.7 W kg-1. Furthermore, the 2D Co3O4 ultrathin nanomeshes show an outstanding performance for the oxygen evolution reaction with an overpotential of 230 mV at the onset potential and a small Tafel slope of 74.0 mV dec-1. The present method presents a facile avenue to the preparation of other 2D ultrathin metal oxide nanostructures with various applications in energy catalysis and conversion.

Rational Design of Co(II) Dominant and Oxygen Vacancy Defective CuCo2O4@CQDs Hollow Spheres for Enhanced Overall Water Splitting and Supercapacitor Performance.

The hierarchical CuCo2O4@carbon quantum dots (CQDs) hollow microspheres constructed by 1D porous nanowires have been successfully prepared through a simple CQDs-induced hydrothermal self-assembly technique. XPS analysis shows the CuCo2O4@CQDs possesses the Co(II)-rich surface associated with the oxygen vacancies, which can effectively boost the Faradaic reactions and oxygen evolution reaction (OER) activity. For example, the as-synthesized 3D porous CuCo2O4@CQDs electrode exhibits high activity toward overall electrochemical water splitting, for example, an overpotential of 290 mV for OER and 331 mV for hydrogen evolution reaction (HER) in alkaline media have been achieved at 10 mA cm-2, respectively. Furthermore, an asymmetric supercapacitor (ASC) (CuCo2O4@CQDs//CNTs) delivers a high energy density of 45.9 Wh kg-1 at 763.4 W kg-1, as well as good cycling ability. The synergy of Co(II)-rich surface, oxygen vacancies, and well-defined 3D hollow structures facilitates the subsequent surface electrochemical reactions. This work presents a facile method to fabricate energetic nanocomposites with highly reactive, durable, and universal functionalities.

Mild synthesis of monodisperse tin nanocrystals and tin chalcogenide hollow nanostructures.

We report a mild synthetic method to access Sn nanocrystals with tunable diameter and narrow size distribution (6-8%). The self-templated formation of various types of Sn chalcogenide hollow nanostructures including oxides, sulfides, selenides, and tellurides is also demonstrated for the first time. The use of air-stable tungsten hexacarbonyl that produces carbon monoxide at elevated temperature to reduce the SnCl2 precursor and coordinate the nanoparticle surface is thought to play an essential role in this method. This synthesis method is likely to be extended to other metal systems and could find potential applications including battery anodes and catalysts.