Oxygen storage and release behavior of delafossite-type CuFe1−x Al x O2

Delafossite-type solid solution, CuFe1−x Al x O2, was synthesized and its oxygen storage capacity (OSC) was investigated under oxidation/reduction cycle using a pulse injection method. CuFe1−x Al x O2 was synthesized by heating at 1100–1150 °C in N2 flow. OSC values for x = 0.1 and 0.3 were larger than that for x = 0 above 500 °C, indicating that substitution of Fe3+ by Al3+ improved OSC. For x = 0.5–1.0, temperature at which OSC increased steeply shifted upward. Results of X-ray diffraction (XRD) after the thermogravimetry and differential thermal analysis (TG–DTA) measurement in air for CuFe1−x Al x O2 (x = 0–0.7) indicated that oxidative decomposition of delafossite phases to CuO and spinel-type phase occurred. In addition, Cu reduction temperature estimated by the temperature programmed reduction using H2 (H2-TPR) shifted to higher temperature with increasing Al content. The XRD results of the samples after H2 and O2/He pulse injection suggested that the oxygen storage/release behavior was caused by reversible oxidation/reduction process between CuFe1−x Al x O2 delafossite and (Fe1−x Al x )3O4 spinel phase +Cu.