Insight into the Structural Variation and Sodium Storage Behavior of Polyoxometalates Encapsulated within Single‐Walled Carbon Nanotubes

Abstract

The host–guest interaction can remarkably alter the physiochemical properties of composite materials. It is crucial to clarify the mechanism by revealing the influence of the host on the electronic structure of the guest molecules. Herein, we study the structural variation of polyoxometalates (POMs) after being confined in single‐walled carbon nanotubes (SWNT). What we found is that in addition to the reported charge transfer from SWNT to POM, an intramolecular electron transfer within a single POM cluster can be observed in the POM@SWNT composites. Moreover, the charge density on the bridged oxygen of POMs is prominently enhanced. The structural change and electron reconfiguration of POMs upon encapsulation in SWNT significantly speed up electron and ion transport, leading to the improved electrochemical performance for sodium ions storage.

Recent Advances in Confining Polyoxometalates and the Applications

“…In addition to the electron transfer between the host and guest, Song's group clarified the influence of the confinement effect on the electronic structure of POM. [ 118 ] They found that after confining in SWCNTs, electron transfer also occurred within a single POM molecule, and more electrons accumulated on the bridged oxygen of POMs. When applied as an anode material for sodium‐ion battery (SIB), the reversible capacity of PMo 12 @SWCNTs electrode was maintained at 210 mA h g −1 after 100 cycles at a current density of 750 mA g −1 .…”

Dynamic evolution of metal nanoclusters revealed by in-situ electron microscopy

“…SWCNTs that encapsulate the POMs clusters strictly limit the molecular motion in two dimensions but enable the intermolecular reactions between pairs of neighboring POM clusters in the third dimension. The encapsulated POM/SWCNT system [105][106][107][108][109] enables the direct observation of cluster rotation [110] and condensation reaction [111] in a fixed dimension.…”

Enhanced performance of a Na3.5Co4[Bi2Co2W19.75O70(H2O)6]/porous graphitic carbon nitride heterojunction based photocatalyst realized by the addition of copper sulfide nanoparticles

“…13 In general, for saturated POMs, the bridge oxygen atoms act as the active sites during a redox reaction, but unfortunately, they can hardly be activated, which severely limits their photocatalytic performance. 14 To solve the problem, by removing one or more MO 6 metal octahedra from the saturated structure, the negative charge of the terminal oxygen at the deletion site remains a fixed-domain state, thus increasing the density of the electron cloud inside the vacant POMs, and finally improving the nucleophilic and catalytic reactivity. Coincidentally, for bismuth POMs, the heteroatom Bi 3+ in its structure forms a triangular cone structure with its three neighbouring oxygen atoms, and because of the presence of a lone pair of electrons at the top of this triangular cone structure, together with the repulsion of identical charges, the resulting stereochemical effect leads to the vacancy of bismuth POMs during the formation process, so that the bismuth POMs are mostly deficient in the structure, 15 which is suitable for use in the construction of photocatalytic composite materials.…”