Pd/Mo₂N-TiO₂ as efficient catalysts for promoted selective hydrogenation of 4-nitrophenol: A green bio-reducing preparation method

The addition of a suitable co-catalyst is an encouraging way to enhance the catalytic performance of Pd based catalyst with low content. Herein, we describe an easy synthesis of Mo₂N-TiO₂ with well-dispersed Mo₂N nanoparticles through one pot evaporation-induced self-assembly and nitridation treatment method. Moreover, a green bio-reductive approach with Catalpa Fruit (CF) extract was adopted to fabricate Pd/Mo₂N-TiO₂ catalysts for promoting selective hydrogenation of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) as model reaction. Among these Pd/Mo₂N-TiO₂ catalysts, 0.8 wt%Pd/Mo₂N-TiO₂ exhibits significantly high catalytic activity for selective hydrogenation of various nitrophenols and cinnmaldehyde. Importantly, the catalytic activity of the catalyst prepared by the reduction method of the CF extract is higher than that prepared by the reduction method of NaBH₄. A serials of characterization, including XRD, N₂ adsorption–desorption, TEM, XPS, CO chemisorption and CO-FTIR etc., was carried out to investigate the influence of the prepared method on the surface Pd species and activity. The high performance can be attributed to the specific nanostructure characteristics of the catalyst and the good synergistic effect between Pd and Mo₂N, improving the dispersion of Pd nanoparticles atoms and the exposure of more active Pd atoms (surface Pd⁰ species) on 0.8 wt%Pd/Mo₂N-TiO₂ due to the CF extract as reductant.