Boosting the plasma catalytic performance of CeO2/γ-Al2O3 in long-chain alkane VOCs via tuning the crystallite size

Abstract

CeO2/γ-Al2O3 catalysts with distinct crystallite sizes were synthesized by changing the precursors of ceria. CeO2/γ-Al2O3 prepared by cerium nitrate (CN) had smaller crystalline size than samples prepared by cerium chloride or cerium acetate. They were evaluated in the plasma catalytic oxidation reaction of n-undecane (C11), which is one of the representative long-chain alkane volatile organic compounds (VOCs). CeO2(CN)/γ-Al2O3 displayed a higher C11 conversion of 100 % with 72 % of CO2 selectivity under ambient conditions with an energy density of 205 J/L, while samples with larger crystalline sizes showed lower activities. X-ray photoelectron spectroscopy analysis confirmed that more concentration of adsorbed oxygen species and higher ratio of Ce3+/(Ce3++Ce4+) existed on the surface of CeO2/γ-Al2O3 samples with smaller crystalline size. Chemisorption experiments further verified that surface oxygen vacancies resulted in the different catalytic activities. In situ diffuse reflectance infrared Fourier transform spectroscopy analyses showed that the oxidation capability of intermediates by-products enhanced with the decrease of crystalline size. Results revealed that the crystallite size of CeO2 had a significant effect on the redox properties. This research provides an insight into the regulation of oxygen vacancy in transition metal oxides to facilitate the plasma catalytic performance of alkane VOCs under mild reaction conditions.