Size- and shape-controlled synthesis and catalytic performance of iron-aluminum mixed oxide nanoparticles for NOx and SO2 removal with hydrogen peroxide

A novel, simple, reproducible and low-cost strategy is introduced for the size- and shape-controlled synthesis of iron-aluminum mixed oxide nanoparticles (NIAO(x/y)). The as-synthesized NIAO(x/y) catalyze decomposition of H2O2 yielding highly reactive hydroxyl radicals ((OH)-O-center dot) for NOx and SO2 removal. 100% SO2 removal is achieved. NIAO(x/y) with Fe/Al molar ratio of 7/3 (NIAO(7/3)) shows the highest NOx removal of nearly 80% at >170 degrees C, whereas much lower NOx removal (<63%) is obtained for NIAO(3/7). The melting of aluminum oxides in NIAO(7/3) promotes the formation of lamellar products, thus improving the specific surface areas and mesoporous distribution, benefiting the production of (OH)-O-center dot radicals. Furthermore, the NIAO(7/3) leads to the minor increase of points of zero charges (PZC), apparent enhancement of FeOH content and high oxidizing ability of Fe(III), further improving the production of (OH)-O-center dot radicals. However, the NIAO(3/7) results in the formation of aluminum surface-enriched spherical particles, thus decreasing the surface atomic ratio,of iron oxides, decreasing (OH)-O-center dot radical production. More importantly, the generation of FeOAl causes the decline of active sites. Finally, the catalytic decomposition of H2O2 on NIAO(x/y) is proposed. And the well catalytic stability of NIAO(7/3) is obtained for evaluation of 30 h. (C) 2014 Elsevier B.V. All rights reserved.