Facile Preparation of MoS2 Nanocomposites for Efficient Potassium-Ion Batteries by Grinding-Promoted Intercalation Exfoliation.

Efficient exfoliations of bulk molybdenum disulfide (MoS2 ) into few-layered nanosheets in pure phase are highly attractive because of the promising applications of the resulted 2D materials in diversified optoelectronic devices. Here, a new exfoliation method is presented to prepare semiconductive 2D hexagonal phase (2H phase) MoS2 -cellulose nanocrystal (CNC) nanocomposites using grinding-promoted intercalation exfoliation (GPIE). This method with facile grinding of the bulk MoS2 and CNC powder followed by conventional liquid-phase exfoliation in water can not only efficiently exfoliate 2H-MoS2 nanosheets, but also produce the 2H-MoS2 /CNC 2D nanocomposites simultaneously. Interestingly, the intercalated CNC sandwiched in MoS2 nanosheets increases the interlayer spacing of 2H-MoS2 , providing perfect conditions to accommodate the large-sized ions. Therefore, these nanocomposites are good anode materials of potassium-ion batteries (KIBs), showing a high reversible capacity of 203 mAh g-1 at 200 mA g-1 after 300 cycles, a good reversible capacity of 114 mAh g-1 at 500 mA g-1 , and a low decay of 0.02% per cycle over 1500 cycles. With these impressive KIB performances, this efficient GPIE method will open up a new avenue to prepare pure-phase MoS2 and promising 2D nanocomposites for high-performance device applications.

Composition- and size-modulated porous bismuth-tin biphase alloys as anodes for advanced magnesium ion batteries.

Rechargeable magnesium batteries have huge potential for applications in large scale energy storage systems due to their low cost and abundant sources. Nevertheless, not much attention has been paid to the development of alternative anodes for magnesium ion batteries (MIBs). Herein, we demonstrate a scalable strategy to fabricate bismuth (Bi)-tin (Sn) biphase anodes with a porous (P) structure and controllable compositions/sizes, through the design of triphase precursors with immiscible elements (with a positive enthalpy of mixing between elements) and selective phase corrosion. Here, one phase was selected as the sacrificial component to form three-dimensional porous channels, which differs from the mechanism by which a porous structure is generated in a classical dealloying process. We systematically investigate how the composition and size of P-Bi-Sn anodes affect their Mg storage properties. As an anode for MIBs, the P-Bi3Sn2 electrode exhibits an excellent reversible capacity retention of over 93% for 200 cycles at 1000 mA g-1. Most importantly, the Mg storage mechanism of P-Bi-Sn anodes was unveiled by operando X-ray diffraction.

A Dealloying Synthetic Strategy for Nanoporous Bismuth-Antimony Anodes for Sodium Ion Batteries.

Metal-based anodes have recently aroused much attention in sodium ion batteries (SIBs) owing to their high theoretical capacities and low sodiation potentials. However, their progresses are prevented by the inferior cycling performance caused by severe volumetric change and pulverization during the (de)sodiation process. To address this issue, herein an alloying strategy was proposed and nanoporous bismuth (Bi)-antimony (Sb) alloys were fabricated by dealloying of ternary Mg-based precursors. As an anode for SIBs, the nanoporous Bi2Sb6 alloy exhibits an ultralong cycling performance (10 000 cycles) at 1 A/g corresponding to a capacity decay of merely 0.0072% per cycle, due to the porous structure, alloying effect and proper Bi/Sb atomic ratio. More importantly, a (de)sodiation mechanism ((Bi,Sb) ↔ Na(Bi,Sb) ↔ Na3(Bi,Sb)) is identified for the discharge/charge processes of Bi-Sb alloys by using operando X-ray diffraction and density functional theory calculations.

Scalable Fabrication of Core-Shell Sb@Co(OH)2 Nanosheet Anodes for Advanced Sodium-Ion Batteries via Magnetron Sputtering.

Antimony (Sb) has captured extensive attention as a promising anode for sodium-ion batteries (SIBs) due to its high theoretical capacity and moderate sodiated potential but is held back from practical applications owing to its pulverization induced by dramatic volumetric variations during the (de)sodiation process. Herein, we report a core-shell Sb@Co(OH)2 nanosheet anode fabricated via magnetron sputtering Sb onto the mass-productive Co(OH)2 substrate anchored on stainless-steel mesh, which is scalable and suitable for flow-line production. In SIBs, the Sb@Co(OH)2 anode displays superior rate performance (383.5 mAh/g at 30 A/g), high discharge capacity, and excellent stability. Compared with the sputtered Sb film electrode, the improved performance of the core-shell Sb@Co(OH)2 nanosheet anode can be attributed to the open framework of the Co(OH)2 substrate, not only accelerating the ion and electron transfer but also serving as the buffer for alleviating the volumetric variation and the supporting scaffold for prohibiting the aggregation. More importantly, the (de)sodiation mechanism of the Sb@Co(OH)2 anode was explored by operando ( in situ) X-ray diffraction, and the similar alloying-dealloying processes (Sb ↔ Na xSb ↔ Na3Sb) for the 1st, 13th, and 30th cycles illustrate the excellent stability of the electrode.

A self-supported nanoporous PtGa film as an efficient multifunctional electrocatalyst for energy conversion.

Pt-based nanomaterials have been widely investigated as efficient electrocatalysts for energy conversion reactions such as small organic molecule oxidation and hydrogen evolution, but are mainly limited to alloys of Pt with transition metals. Herein, a new PtGa electrocatalyst with unique nanoporous architecture and a self-supported feature (np-PtGa) was fabricated via a liquid Ga-assisted dealloying strategy. Owing to the unique nanoporous structure and alloying effect by the introduction of Ga, the np-PtGa alloy exhibits excellent electrocatalytic activities towards the electrooxidation of methanol, ethanol, ethylene glycol, glycerol, and formic acid, which are three orders of magnitude higher than those of the benchmark Pt foil. Moreover, our np-PtGa alloy displays extraordinary catalytic activities towards the hydrogen evolution reaction in both acidic and alkaline environments. Impressively, the overpotential of np-PtGa is as low as 50 mV at 10 mA cm-2 with a Tafel slope of 55 mV dec-1 in 1 M KOH, outperforming most of the recently reported electrocatalysts. Density functional theory calculations demonstrate that the downshift of the d-band center caused by the Ga 4p/Pt 5d orbital hybridization and compressive stress could weaken the adsorption of intermediate species and well rationalize the enhanced electrocatalytic performance of np-PtGa.

'Painting' nanostructured metals-playing with liquid metal.

Materials scientists always dream to 'paint' nanostructured metal on a metallic foil, just as artists paint a painting on a canvas. Herein, we have, for the first time, realized this dream using liquid gallium (Ga) as the paint. Through a liquid Ga stimulated painting-alloying-dealloying strategy, seven kinds of nanostructured metallic films including Au, Ag, Pd, Pt, Cu, Co, and Ni were generally fabricated and supported on the corresponding metallic foils. Owing to the painting-like operation, nanostructured films with complicated patterns and large sizes (up to meters) were successfully produced without any shape/size limitations. The nanostructured metallic films possess advantages like their unique nanoporous structures, self-supporting nature, good continuity, flexibility and high specific surface areas, and could serve as robust electrodes in devices like batteries, fuel cells, water splitting electrolyzers, etc. Moreover, the proposed strategy shows great potential in the fabrication of other self-supporting, flexible, advanced nanomaterials.