Carboxyethyltin and transition metal co-functionalized tungstoantimonates composited with polypyrrole for enhanced electrocatalytic methanol oxidation

Abstract

Carboxyethyltin and first-row transition metals (TMs) were firstly introduced into trivacant Keggin-type tungstoantimonate in an aqueous solution, leading to the formation of four crystalline organic–inorganic hybrid sandwich-type polyoxometalates (POMs), formulated as Na_10−x−yK_yH_x[((TM)(H₂O)₃)₂(Sn(CH₂)₂COO)₂(SbW₉O₃₃)₂]·nH₂O (SbW₉-TM-SnR, TM = Mn, Co, Ni, Zn; x = 1, 1, 0, 0; y = 0, 5, 5, 2; n = 18, 24, 24, 22, respectively). SbW₉-TM-SnR exhibit high catalytic ability for the oxidation of cyclohexanol. Meanwhile, SbW₉-TM-SnR were composited with polypyrrole (PPy) through an electropolymerization process, forming PPy-SbW₉-TM-SnR, on which platinum (Pt) was further electro-deposited to prepare PPy-SbW₉-TM-SnR/Pt for electrocatalytic methanol (CH₃OH) oxidation in acid solution. The composition and morphology of PPy-SbW₉-TM-SnR/Pt were determined by IR, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The electrochemical experimental results show that SbW₉-TM-SnR and PPy obviously enhance the electrocatalytic and anti-intoxication abilities of Pt, and the highest peak current density of 0.87 mA cm⁻², corresponding to 1.85 and 1.43 times higher than those of pure Pt and PPy/Pt electrodes respectively, is acquired for the PPy-SbW₉-Ni-SnR/Pt composite electrode. These findings may enlarge the application of PPy and POMs in the electrocatalytic field.