Catalysis and proton-conduction of novel phosphate glasses

• Published in: Journal of non-crystalline solids 2009-06, Vol.355 (16), p.960-964
• Main Authors: Mizusaki, S., Toyoda, Y., Nakayama, K., Nagata, Y., Ozawa, T.C., Noro, Y., Samata, H.
• Format: Article
• Language: English
• Subjects: Adsorption; Catalysis; Chemistry; Conductivity; Exact sciences and technology; General and physical chemistry; Hydrogen in glass; Oxidation reduction; Phosphates; Raman scattering; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Water
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2009.04.012

The performance of phosphate glasses as a catalyst for water decomposition and a proton conductor was investigated. Glasses with a composition of 30Na 2O–10BaO–30P 2O 5–(30− x)WO 3– xNb 2O 5 (5 < x < 25) decompose water vapor and generate hydrogen at 500 °C. The best decomposition performance was observed on a specimen with the Nb 2O 5 composition of x = 15. A part of hydrogen produced on the glass surface changes to protons by reducing W 6+ ions and penetrates into the glass. The electron is the dominant charge carrier in the electric conduction of W-rich glasses, whereas proton conduction is predominant in Nb-rich glasses in hydrogen atmosphere. A Raman scattering experiment revealed that Nb contributes to depolymerize the –P–O–P– chains in the phosphate glass producing non-bridging oxygen. A possible model was proposed for the water decomposition and proton conduction processes.