A novel Au/electroactive poly(amic acid) composite as an effective catalyst for p-nitrophenol reduction

In Situ Redox Synthesis of Highly Stable Au/Electroactive Polyimide Composite and Its Application on 4-Nitrophenol Reduction

In this study, we developed a series of Au/electroactive polyimide (Au/EPI-5) composite for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) using NaBH₄ as a reducing agent at room temperature. The electroactive polyimide (EPI-5) synthesis was performed by chemical imidization of its 4,4'-(4.4'-isopropylidene-diphenoxy) bis (phthalic anhydride) (BSAA) and amino-capped aniline pentamer (ACAP). In addition, prepare different concentrations of Au ions through the in-situ redox reaction of EPI-5 to obtain Au nanoparticles (AuNPs) and anchored on the surface of EPI-5 to form series of Au/EPI-5 composite. Using SEM and HR-TEM confirm the particle size (23-113 nm) of the reduced AuNPs increases with the increase of the concentration. Based on CV studies, the redox capability of as-prepared electroactive materials was found to show an increase trend: 1Au/EPI-5 < 3Au/EPI-5 < 5Au/EPI-5. The series of Au/EPI-5 composites showed good stability and catalytic activity for the reaction of 4-NP to 4-AP. Especially, the 5Au/EPI-5 composite shows the highest catalytic activity when applied for the reduction of 4-NP to 4-AP within 17 min. The rate constant and kinetic activity energy were calculated to be 1.1 × 10^-3 s^-1 and 38.9 kJ/mol, respectively. Following a reusability test repeated 10 times, the 5Au/EPI-5 composite maintained a conversion rate higher than 95%. Finally, this study elaborates the mechanism of the catalytic reduction of 4-NP to 4-AP.

High-efficiency reduction of p-nitrophenol on green-synthesized gold nanoparticles decorated on ceria nanorods

A green synthesis using extract from Citrus maxima peel was developed to fabricate Au–Ce catalysts for the reduction of p-nitrophenol (PNP). Au nanoparticles with a diameter of 6.6 ± 2.5 nm were deposited onto the surface of CeO₂ nanorods with a length of 33.1 ± 15.0 nm and a diameter of 7.1 ± 2.1 nm. The mesoporous and non-porous capillary structures of these materials were observed. The interaction between Au and CeO₂ increased the specific surface area, pore diameter, and pore volume compared with pure CeO₂ (90 m² g⁻¹, 23.8 Å, and 0.110 cm³ g⁻¹versus 72 m² g⁻¹, 23.0 Å, and 0.089 cm³ g⁻¹). The splitting peaks of the surface oxygen and their shifting at lower temperatures compared with CeO₂ nanorods were found thanks to the Au–CeO₂ interaction, suggesting that their reduction occurred more easily. The synthesized Au–Ce catalysts exhibited excellent activity in the reduction of PNP to p-aminophenol. The 0.2Au–Ce catalyst was the most efficient one for PNP reduction, enabling the conversion of PNP in 30 minutes with a catalyst concentration of 20 mg L⁻¹ and a PNP/NaBH₄ molar ratio of 1/200. Moreover, the 0.2Au–Ce catalyst could be reused for at least five consecutive cycles without considerable loss of its activity.

A green synthesis using extract from Citrus maxima peel was developed to fabricate Au–Ce catalysts for the reduction of p-nitrophenol (PNP).