Issue 30, 2006

Layered Pr-dodecyl sulfate mesophases as precursors of Pr2O2SO4 having a large oxygen-storage capacity

Abstract

Surfactant-assisted synthesis of the oxysulfate Pr2O2SO4 with a large oxygen-storage capacity was studied with the aim of increasing the rate of redox cycles at lower temperatures. From an aqueous solution of nitrate, Pr-based surfactant mesophases templated by dodecyl sulfate anion (DS = C12H25OSO3) were synthesized using ammonia or urea as precipitants. The precipitated mesophases, Pr-DS-NH3 and Pr-DS-N2H4CO, exhibited ordered layered structures with interlayer spacings of 2.63 and 3.68 nm, respectively, suggesting alternative stacking of a Pr hydroxide layer and a DS layer. The different interlayer spacing can be explained by the fact that Pr-DS-NH3 with the composition Pr2(OH)5(DS)·2.5H2O contains monolayers of DS, whereas Pr-DS-N2H4CO contains bilayers of DS. As was revealed by EXAFS and FT-IR results, the sulfate head group of each DS is strongly bound to uncoordinated Pr3+, so that heating of Pr-DS-NH3 could directly yield single-phase Pr2O2SO4 at a low temperature (500 °C). In contrast to the macropores (≥12 nm in size, 8 m2 g−1) of Pr2O2SO4 prepared by calcining Pr2(SO4)3, Pr-DS-NH3 after calcination showed pores of 2–3 nm in size and a larger surface area (28 m2 g−1). The microstructure is very effective in accelerating the solid–gas reaction in oxygen release as well as storage processes, which enables the present system to work at temperatures ≤600 °C, compared to ≥700 °C required for Pr2O2SO4 prepared from Pr2(SO4)3.

Graphical abstract: Layered Pr-dodecyl sulfate mesophases as precursors of Pr2O2SO4 having a large oxygen-storage capacity

Article information

Article type
Paper
Submitted
18 Apr 2006
Accepted
13 Jun 2006
First published
23 Jun 2006

J. Mater. Chem., 2006,16, 3084-3090

Layered Pr-dodecyl sulfate mesophases as precursors of Pr2O2SO4 having a large oxygen-storage capacity

M. Machida, K. Kawamura, T. Kawano, D. Zhang and K. Ikeue, J. Mater. Chem., 2006, 16, 3084 DOI: 10.1039/B605518D

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