Preparation of Nanogold/Graphene Oxide/Chitosan Hydrogels and Their Performance in Catalytic Reduction of 4-Nitrophenol

Gold nanoparticles/graphene oxide/chitosan (GO/CHS) hydrogels (AuNPs/GO/CHS) were prepared by in situ reduction of chloroauric acid using graphene oxide/chitosan (GO/CHS) hydrogels as the carrier. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and specific surface and porosity analyses were used to characterize AuNPs/GO/CHS. The effect of AuNPs/GO/CHS prepared from chitosan with different degrees of deacetylation and molecular weights on the catalytic reduction of 4-nitrophenol (4-NP) was investigated using NaBH₄ as a hydrogen donor.The results showed that GO improved the catalytic activity of AuNPs, and the catalytic reduction of 4-NP by AuNPs/CS and AuNPs/GO/CS satisfies the pseudo-primary reaction kinetics with rate constants of 0.027 0 and 0.157 0 min^-1, respectively, and conversions of 55.7% and 93.7% at 30 min of reaction. The low-deacetylation degree and low molecular weight chitosan-prepared catalysts with low deacetylation degree and low molecular weight chitosan had higher 4-NP catalytic activity. When AuNPs/GO/N2 prepared from chitosan with a deacetylation degree of 64% was used as the catalyst, the conversion of 4-NP could reach 97.7% with a rate constant k of 0.230 9 min^-1 and an activation energy E_a of 37.2 kJ·mol^-1 for 30 min at 30 ℃. The catalysts with a low deacetylation degree and low molecular weight had higher 4-NP catalytic activity.