Publications (3)6.32 Total impact
Article: Cooperativity of copper and molybdenum centers in polyoxometalate-based electrocatalysts: cyclic voltammetry, EQCM, and AFM characterization.[show abstract] [hide abstract]
ABSTRACT: Electrochemical behaviors of selected Dawson-type polytungstates including 2-K10[P2W15Mo2O61box] where the symbol [box] designates a vacant site, alpha2-K7[Fe(OH2)P2W15Mo2O61], alpha2-K8[Cu(OH2)P2W15Mo2O61], alpha1- and alpha2-K8[Cu(OH2)P2W17O61], alpha2-K8[Cu(OH2)P2W13Mo4O61], and alpha2-K8[Cu(OH2)P2W12Mo5O61] were investigated by cyclic voltammetry (CV) coupled with the electrochemical quartz microbalance (EQCM), and the results were completed by atomic force microscopy (AFM) observations of the electrodeposited films. The electrocatalytic abilities of these polyoxometalates (POMs) in the reduction of dioxygen, hydrogen peroxide, and NOx were also assessed by CV and EQCM. It turns out that the remarkable electrocatalysis obtained at the reduction potential of Mo centers within alpha2-K8[Cu(OH2)P2W15Mo2O61], but in a domain where Cu2+ is not deposited, benefits from the assistance of the copper center because such catalysis could not be observed in the absence of Cu2+. EQCM confirms that no copper deposition occurs under the experimental conditions used. Analogous behaviors are encountered in the electrocatalytic reduction of nitrite where assistance by the presence of the Cu2+ center induced the observation of catalysis at the potential location of Mo centers. Finally, the reduction of nitrate is triggered by electrodeposited copper but was remarkably favored by the presence of molybdenum atoms within these polyoxometalates (POMs). All of the results converge to indicate a cooperative effect between the Mo and Cu centers within these POMs. The various results suggest that copper deposition from these POMs should give morphologically different surfaces. AFM studies confirm this expectation, and the observed morphologies and sizes of particles were rationalized by taking into account the role of the POM skeleton and its atomic composition in the electrodeposition process.Langmuir 01/2007; 22(25):10416-25. · 4.19 Impact Factor
Article: Electrochemically induced transformations of heteropolyanions: new electroactive metal oxide films studied by the electrochemical quartz crystal microbalance[show abstract] [hide abstract]
ABSTRACT: New oxide films have been electrodeposited from [P2Mo18O62]6− by potential cycling in mildly acidic aqueous media. To obtain an adherent and persistent film, it is necessary that more than six electrons/molecule be fixed on the framework of the heteropolyanion. The film is then studied in pure supporting electrolyte. In this medium, a remarkable current increase is observed during the potential cycling. Whether the film is deposited on a glassy carbon electrode or on the gold electrode of an electrochemical quartz crystal microbalance (EQCM), exactly the same steady current increase up to a maximum is obtained in cyclic voltammetric measurements. The EQCM reveals a steady mass increase during the continuous cycling of the film in the supporting electrolyte. This behaviour is interpreted as featuring an irreversible water and electrolyte intake into the film, up to a maximum, after which the phenomena observed during reduction and oxidation processes are taken as featuring intercalation/deintercalation, respectively. This behaviour is much the same as described in the literature for WO3 and MoO3 bronzes, except that the present films seem very stable and have shown no tendency to dissolve or deactivate.Journal of Solid State Electrochemistry 08/1999; 3(7):446-456. · 2.13 Impact Factor
Article: First examples of efficient participation of selected metal-ion-substituted heteropolyanions in electrocatalytic nitrate reduction[show abstract] [hide abstract]
ABSTRACT: For the first time, to our knowledge, the electrocatalytic reduction of nitrate is achieved using heteropolyanions. Cu2+- and Ni2+-containing Dawson-type polyoxometalates proved efficient in this issue. The presence of these substituents seems necessary, in contrast with the observed catalytic reduction of nitrite and nitric oxide for which even non-substituted heteropolyanions were active. With the first series of derivatives, the electrocatalysis is triggered by the electrodeposited copper; Ni2+-containing heteropolyanions mimic more closely the catalytic reduction of nitrate by metal ion cyclams and related complexes.Electrochemistry Communications.