Enhanced Catalytic Denitrification Performance of Ruthenium-based Catalysts by Hydrogen Spillover from a Palladium Promoter

Catalytic denitrification, a promising technology for nitrate removal, is increasingly limited by the rising price of Pd. Replacing Pd with less-expensive Ru would significantly reduce the cost; however, Ru-based catalysts have been reported to perform inconsistently in denitrification applications, making their replacement prospects unclear. Herein, the surface oxidation of Ru catalysts was confirmed to be a key factor that inhibits activity. A series of Ru-Pd catalysts containing small amounts of Pd (0.5 wt%) was developed to eliminate the Ru surface-oxide layer through the spillover of hydrogen atoms activated on the Pd promoter. Ru-Pd/Fe3O4 exhibited superior catalytic activity to Ru-Pd/C and Ru-Pd/Al2O3 because the reducible carrier (Fe3O4) has a lower resistance to hydrogen spillover and diffusion, as determined experimentally and supported by density functional theory calculations. This study developed a method that eliminates ruthenium surface oxides in situ and restores its denitrification activity, further reducing the barrier to Ru replacing Pd in catalytic aqueous denitrification. (c) 2021 Elsevier Inc. All rights reserved.