Pore morphology evolution and atom distribution of doped Fe2O3 foams developed by freeze-casting after redox cycling

TL;DR

This study develops doped Fe2O3 foams via freeze-casting with camphene suspension to enhance stability and pore structure for chemical looping water splitting, analyzing pore evolution and redox performance.

Contribution

It introduces a freeze-casting method with camphene suspension to produce stable, highly porous doped Fe2O3 foams for improved redox cycling in hydrogen production.

Findings

Doped Fe2O3 foams maintain pore structure after redox cycles.

Al doping prevents core-shell structure formation.

Initial pore size above 100 microns reduces densification.

Abstract

Chemical looping water splitting systems operate at relatively high temperatures (450-800 degree C) to produce, purify, or store hydrogen by the cyclic reduction and oxidation (redox) of a solid oxygen carrier. Therefore, to improve long-term operation, it is necessary to develop highly stable oxygen carriers with large specific surface areas. In this work, highly interconnected doped Fe2O3 foams are fabricated through the freeze-casting technique, and the aid of a submicrometric camphene-based suspension to prevent Fe sintering and pore clogging during redox operation. The influence of the dopant elements (Al and Ce) over the pore morphology evolution, and redox performances are examined. The use of an Fe2O3 porous structure with initial pore size above 100 microns shows a significant reduction of the sample densification, and the addition of Al2O3 by the co-precipitation process proves to be beneficial in preventing the generation of a core-shell structure following redox processing.