In situ preparation of highly dispersed Pd supported on exfoliated layered double hydroxides via nitrogen plasma for 4-nitrophenol reduction.

In this work, a simple and environmental-friendly nitrogen glow discharge plasma reduction method has been developed for synthesizing palladium nanoparticles (PdNPs) supported on exfoliated Mg-Al-layered double hydroxide (Pd/LDH) catalysts. The as-prepared catalysts were characterized by means of characterizations methods, which contain X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectrometry (XPS), and Fourier transform infrared (FT-IR). Highly dispersed ultrafine PdNPs were supported on exfoliated, defect-induced LDHs uniformly without agglomeration. The effects of treatment time of nitrogen plasma and Pd loading amount on structure, morphology, and catalytic performance of Pd/LDHs were investigated. The comparisons of structure and morphology between LDHs and Pd/LDHs were also discussed. The average particle size of as-synthesized PdNPs with face-centered cubic structure is 2.01 nm, which ranges from 1.18 to 3.01 nm. Nitrogen plasma cannot only reduce Pd, but also exfoliate LDHs, introduce defects, and even destroy the structure of LDHs. The Pd/LDH catalyst with 1 wt% Pd loading under nitrogen plasma treatment for 60 min showed the best catalytic performance in 4-nitrophenol reduction. The turnover frequency (TOF) of as-prepared catalyst is 20-fold higher than that of commercial Pd/C catalyst.