Bimetallic Ag–Ir/CeO₂–Fe₂O₃ Nanostructured Catalysts with Single-Atom Species for Room-Temperature Nitrophenol Reduction

The preparation of catalysts that can effectively operate under mild conditions remains a challenge in accordance with green chemistry principles. Here, a series of nanostructured CeO2–Fe2O3-supported Ag–Ir bimetallic catalysts with a low total content of metals (2 wt %) is prepared and tested in 4-nitrophenol reduction into 4-aminophenol at room temperature and atmospheric pressure. The 1Ir–1Ag/CeO2–Fe2O3 sample shows the highest activity (k = 1.11 min–1), which significantly exceeds those of monometallic Ag and Ir counterparts due to the synergistic effect between highly dispersed 2 nm silver nanoparticles and single-atom and cluster iridium species. The interaction of the two metals is confirmed by H2-TPR and UV–vis spectroscopy and results in a shortening of the induction period and enhanced catalytic activity. The results obtained can serve as a ground to prepare more affordable catalysts, where expensive Ir is partially substituted by more affordable Ag.