Electronic Interface Interaction on Al ₂ O ₃ /Ag Inverse Catalysts for Enhanced Catalytic Reduction of 4-NP

Electronic interface interaction (EII) plays an important role in regulating the structure–function relationship of metal/oxide heterogeneous catalytic systems. In this work, we prepared Al 2 O 3 /Ag inverse oxide/metal catalysts with a facile synthetic method without using any organic ligand. The composites were supported by well-defined silver nanocubes (Ag NCs) and covered by an oxide layer with variable coverage as confirmed by transmission electron microscopy (TEM) and high-sensitivity low-energy ion scattering spectroscopy (HS-LEIS) characterizations. The catalytic performance toward the reduction of 4-nitrophenol (4-NP) in excess NaBH 4 obviously enhanced with increasing coverage of alumina overlayer; the composite principally provided more surface adsorption sites for reactants, confirmed by the increasing saturated adsorption capacity toward 4-NP. In comparison with pristine Ag NCs and bulk Al 2 O 3, optimized Al 2 O 3 /c-Ag showed superior catalytic performance with about complete conversion of 4-NP within 2 min, keeping high stability for six cycles; the reaction possessed lower apparent activation energy (35.0 kJ/mol), and the corresponding pseudo-first-order kinetic rate constant (2.11 min –1 ) was about 3.27 times greater than that of Ag NCs (0.65 min –1 ). In addition, X-ray photoelectron spectroscopy (XPS) characterization indicated that overall Ag 3d peaks shifted to lower binding energy with increasing percentage of oxide layer, indicating an inclination of metal–oxide interface electron transfer, and Ag NCs acted as a charge contributor, thus directly influencing the catalytic performance in such an electron inducing reaction. This report provides a profound understanding of the electronic interaction between metal and nonreducible oxides, helping to construct a more efficient and stable silver-based catalyst for catalytic reduction of aromatic nitro compounds.