Copper single atoms decorated iridium nanoparticles for the selective hydrogenation of bromonitrobenzene

The interaction between metals is an important factor to modify the catalytic roles of metallic catalysts, and it is highly desirable to reveal the relationship between metal-metal interaction and catalytic performance. Three types of Ir-Cu catalysts including Cu single atoms modified Ir nanoparticles and Ir-Cu alloy catalysts are prepared to observe the modifying role of Cu on Ir. Under relatively high temperature treatment, Ir-Cu alloy can be produced from Cu single atoms and Ir nanoparticles. The selectivity to bromoaniline (BAN) over Cu/C-Ir catalyst can be up to 99.9 % at the 100 % conversion of bromonitrobenzene (BNB), which is higher than that over Ir/C (94.3 %) and Ir-Cu/C alloy catalyst (98.5 %). The turnover frequencies (TOFs) of Cu/C-Ir catalysts are evidently lower than that of the Ir-Cu/C alloy catalyst, though their dispersions are higher than that of Ir-Cu/C alloy catalyst. The electronic transfer from Cu single atoms to Ir nanoparticles not only weakens the hydrogen adsorption ability but reduces the number of active sites available for splitting hydrogen molecules into hydrogen atoms, leading to a decrease in the catalytic activity for the selective hydrogenation of BNB. The interaction exerted by unalloyed Cu single atoms on Ir nanoparticles differs from that of alloyed Cu on Ir, which may be the possible reason for the different catalytic performance between Cu single atoms modified Ir nanoparticles and Ir-Cu alloy.