The applications of polyoxometalate-functionalized nanocarbon materials (carbon nanotubes or graphene) in electrocatalysis and electrochemical energy conversion and storage as well as in sensor systems are reviewed.

Single-walled carbon nanotubes (SWNTs) covalently functionalized with redox-active organo-modified polyoxometalate (POM) clusters have been synthesized and employed as electrode materials in lithium ion batteries. The Anderson cluster [MnMo6 O24 ](9-) is functionalized with Tris (NH2 C(CH2 OH)3 ) moieties, giving the new organic-inorganic hybrid [N(nC4 H9 )4 ]3 [MnMo6 O18 {(OCH2 )3 CNH2 }2 ]. The compound is then covalently attached to carboxylic acid-functionalized SWNTs by amide bond formation and the stability of this nanocomposite is confirmed by various spectroscopic methods. Electrochemical analyses show that the nanocomposite displays improved performance as an anode material in lithium ion batteries compared with the individual components, that is, SWNTs and/or Anderson clusters. High discharge capacities of up to 932 mAh g(-1) at a current density of 0.5 mA cm(-2) can be observed, together with high long-term cycling stability and decreased electrochemical impedance. Chemisorption of the POM cluster on the SWNTs is shown to give better electrode performance than the purely physisorbed analogues.

An organo-functionalized polyoxometalate (POM)-pyrene hybrid (Py-Anderson) has been used for noncovalent functionalization of carbon nanotubes (CNTs) to give a Py-Anderson-CNT nanocomposite through π-π interactions. The as-synthesized nanocomposite was used as the anode material for lithium-ion batteries, and shows higher discharge capacities and better rate capacity and cycling stability than the individual components. When the current density was 0.5 mA cm(-2), the nanocomposite exhibited an initial discharge capacity of 1898.5 mA h g(-1) and a high discharge capacity of 665.3 mA h g(-1) for up to 100 cycles. AC impedance spectroscopy provides insight into the electrochemical properties and the charge-transfer mechanism of the Py-Anderson-CNTs electrode.

Carbon nanotubes (CNTs) possess excellent structural and electronic properties and have been widely investigated as anode materials. Polyoxometalates (POMs) exhibit superior physical properties such as electronic versatility, redox characteristics and unique molecular structures. In this paper, we report the covalent modification of carbon nanotubes (CNTs) with organosilica-containing polyoxometalate (POM) of [Bu4N]4[SiW11O39{O(SiCH2CH2CH2NH2·HCl)2}] (SiW11-NH2) that leads to the formation of the nanocomposite material of CNTs-SiW11, which has been characterized by FT-IR, XRD, HR-TEM, XPS and Raman spectrum, etc. At a current density of 0.5 mA cm(-2), the application of CNTs-SiW11 nanocomposite as anode material in lithium batteries exhibits the first discharge capacity of 1189 mA h g(-1), and the second discharge capacity of 650 mA h g(-1), which remains stable up to 100 cycles. The CNTs-SiW11 nanocomposite exhibits high discharge capacity, good capacity retention and cycling stability.