Solid-state electrochemical generation and characterization of catalytic Pt microcenters within single crystal of heteropoly phospho-12-tungstic acid

• Published in: Electrochimica acta Vol. 44; no. 8; pp. 1295 - 1300
• Main Authors: Kulesza, Pawel J., Karwowska, Beata, Grzybowska, Bozena, Wieckowski, Andrzej
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Oxford Elsevier Ltd 01-12-1998; Elsevier
• Subjects: Chemistry; Chloroplatinate reduction; Electrochemistry; Electrodes: preparations and properties; Exact sciences and technology; General and physical chemistry; Generation of Pt microcenters; Intrastructural proton discharge; Mediation; Other electrodes; W(VI, V) mixed-valence sites; Intrastructural proton discharge; Generation of Pt microcenters; Mediation; Chloroplatinate reduction; W(VI, V) mixed-valence sites; Heteropolysalt; Mixed oxidation number; Hydronium compounds; Dispersed material; Experimental study; Metal particle; Single crystal; Electrodes; Chemical reduction; Electrocatalysis; Platinum; Tungsten V Tungsten VI Complexes; Electrochemical reaction; Catalyst activity; Modified material
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/S0013-4686(98)00251-5

Chloroplatinic acid can be incorporated at trace (10
−5–10
−4 mol dm
−3) levels into the secondary, hydrated, structure of a single crystal of tetragonal phospho-12-tungstic acid, H
3PW
12O
40·29H
2O, without any change of the primary structure of the system. During partial reduction of heteropoly tungstate units, mixed-valence W(VI, V) sites are generated; they are capable to mediate the reduction of chloroplatinate to metallic platinum. Consequently, trace amounts of highly dispersed Pt microcenters are produced in the secondary structure of the crystal. Solid-state electrochemical characterization of the material is accomplished with the use of a carbon fiber ultramicrodisk electrode. The system's first, most positive, one-electron redox reaction is virtually not affected by traces of Pt in the crystal. By performing voltammetric experiments in two time regimes, we have determined concentration of mixed-valence sites and an effective diffusion coefficient for charge propagation. At more negative potentials, intrastructural discharge of hydronium ions at catalytic Pt microcenters is observed.