New Organic−Inorganic Nanocomposite Materials for Energy Storage Applications

A method is described by which the disulfide dimer of 2,5-dimercapto-1,3,4-thiadiazole (diDMcT, see Scheme 1) can be oxidatively intercalated into the layered structure of a V 2 O 5 xerogel. This intercalation reaction produces a new organic−inorganic composite material with a layer spacing of 13.5 Å, in contrast to the 11.55 Å spacing for the parent V 2 O 5 xerogel. During this oxidative intercalation, the diDMcT is polymerized to produce a polymer with thiadiazole rings linked by disulfides in the polymer main chain (PDTT, see Scheme 1). The composite material is characterized by UV−visible spectroelectrochemistry, X-ray diffraction, FTIR, and electrochemistry. The electrochemical experiments comprised charging (oxidation) and discharging (reduction) of the material, with the bulk of the redox reaction occurring over a broad potential range of 0.5 to −0.6 V versus saturated calomel electrode. The cyclic voltammogram of the composite material shows features that can be attributed to the DMcT−PDTT redox response. However, during or after reduction of the composite, the monomeric DMcT dithiolate appears to be expelled from the V 2 O 5 interlayer region, leading to an evolution of the electrochemical response back to that of the original V 2 O 5 material. Evidence is presented suggesting that the V 2 O 5 host material facilitates the redox reactions of the thiol−disulfide redox couple while it is within the interlayer region.