Comparison of sulfated and phosphated zirconia on proton conductivity: Effect of surface acidic properties

Pin Hsin Sung*, Su-Min Chang

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

Abstract

Sulfated (S-) and phosphated zirconia (P-ZrO2) have been demonstrated as promising proton exchange membranes in fuel cell application because of high density of surface acid sites, anhydrous proton transport and high thermal stability. However, comparison of S- and P-ZrO2 on their proton conductivities has not addressed yet. In this study, we prepared mesoporous S- and P-ZrO2 with MCM41 structure and characterized their physicochemical properties and proton conductivities at different surface contents of S and P. Moreover, the proton conductivities of these two solid acids with respect to their surface acidic properties are clarified. The AC impendence spectra show that all the S- and P-ZrO2 perform high proton conductivities (1.4×10-3∼ 3.1×10-3 Scm-1) at room temperature and low water content. The proton conductivity gets linear dependence on ion exchange capacity (IEC). At equal proton conductivity, however, the S-ZrO2 exhibits 4 times lower ICE than P-ZrO2. Pyridine chermisorption on the S-ZrO2 shows Lewis and Bronsted acidic sites at 1450 and 1540 cm-1, while the P-ZrO2 only contains Brönsted acidic sites at 1540 cm-1. In addition, the P-ZrO2 contains more amounts of OH groups than S-ZrO2. These results clearly indicate that surface acidity, rather than density of acid sites, dominates proton diffusion. The S-ZrO2 with high surface acidity is favorable for high surface diffusion of protons resulting in high proton conductivity at low ICE.

Original languageEnglish
Title of host publicationAmerican Chemical Society - 236th National Meeting and Exposition, Abstracts of Scientific Papers
StatePublished - Aug 2008
Event236th National Meeting and Exposition of the American Chemical Society, ACS 2008 - Philadelpia, PA, United States
Duration: 17 Aug 200821 Aug 2008

Publication series

NameACS National Meeting Book of Abstracts
ISSN (Print)0065-7727

Conference

Conference236th National Meeting and Exposition of the American Chemical Society, ACS 2008
Country/TerritoryUnited States
CityPhiladelpia, PA
Period17/08/0821/08/08

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