Anchoring of Pd nanoparticles over amines grafted 3D TiO2 catalyst for the improved selective hydrogenation of 4-nitrophenol

The fabrication of small Pd nanoparticles (NPs) anchored on titanium dioxide (TiO 2 ) supports remains a great challenge due to its high surface energy. Herein, flower-like three dimensional (3D) TiO 2 microstructures assembled from needle flakes are fabricated thru a facile evaporation-induced assisted hydrothermal method, and then modified with amines group (3D-TiO 2 -NH 2 ). Small and uniform dispersed Pd nanoparticles were anchored on the surface of 3D-TiO 2 -NH 2 supports using polyol reduction method. Remarkably, the obtained 3D-TiO 2 -NH 2 supported Pd-based catalyst (Pd@3D-TiO 2 -NH 2 ) demonstrated an optimal 4-NP catalytic hydrogenation efficiency ( k  = 1.09 min −1 ), which is 1.56 and 3.52 times superior than that of the Pd@3D-TiO 2 ( k  = 0.699 min −1 ) and Pd@TiO 2 –P25 ( k  = 0.31 min −1 ) catalysts, respectively. In-depth investigation of the structure-property relationship by SEM, XRD, N 2 adsorption-desorption isotherm, TEM, XPS, CO chemisorption and CO-FTIR reveal that the optimal catalytic hydrogenation activity of Pd@3D-TiO 2 -NH 2 can be credited to its 3D hierarchical structure (interconnected needle flakes) and the amines group existing on the surface of flower-like three dimensional hierarchical TiO 2 , which control the Pd particles size (2.7 nm) and uniform dispersion (43.5%) to generate more surface active Pd 0 entities over Pd@3D-TiO 2 -NH 2 .