Inorganic–organic hybrid polyoxometalate nanoparticle modified gold electrode: Preparation and electrocatalysis

Polyoxometalates (POMs) are a large and rapidly growing class of compounds that have attracted much attention in catalysis, medicine, bioanalysis and materials science owing to their chemical, structural and electronic versatility [1]. In recent years electrochemical properties of POMs have been intensively studied [2]. An important reason is the ability of POMs anions to accept various numbers of electrons giving rise to mixed-valency species, which has made these compounds very attractive in electrode modification and electrocatalytic research [2]. Immobilization of POMs on electrodes not only simplifies their electrochemical study but also facilitates their applications [3]. In general, there are three main strategies for POMs immobilization: (a) Electrochemical deposition [4], only on metal electrode. (b) Immobilization as a dopant in conductive polymeric matrices [5]. (c) Adsorption. POMs are able to adsorb on the surface of carbon-based materials, gold and mercury. The coated electrodes can be rinsed without loss of the POMs coating, which is actively mediating the reduction of bromate, chromate, hydrogen peroxide, and nitrite just as in the case of the dissolved POMs. In this paper, in order to improve the stability of the POM modified electrode, we designed and prepared a kind of inorganic– organic hybrid POM-based L-cysteine-doped tungstophosphate ([(L-cys)3PW12O40]) self assembled monolayer on gold electrode and investigated its electrochemical characteristics and electrocatalytic activity for the reduction of nitrite.