Off-stoichiometric copper-chromium delafossite featuring giant catalytic degradation of ozone is demonstrated for the very first time. This leads to the reversible low-temperature detection of ozone onto resistive thin-film devices to values as low as 50 ppb. The selectivity when compared with molecular oxygen is also evidenced. Near-Atmospheric Pressure X-Ray Photoelectron Spectroscopy led to the understanding of the ozone - Cu0·66Cr1·33O2 surface reaction. The partial oxidation of copper into Cu2+ dependence on the ozone concentration is for the first time revealed. The apparition of a new peak associated with chemisorbed oxygen proves that the specific sub-stochiometric copper sites of the delafossite phase are driving the efficient and selective catalytic decomposition of ozone into monoatomic oxygen at the neat surface of thin films. The sensing response in ambient air is not limited by ozone decomposition but by the number of available adsorption sites. This work discloses pioneering results for the sensing networks integration of competitive ozone sensors based on Cu0·66Cr1·33O2.
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