Optimized Preparation of Gold Nanoparticles-loaded Carbon Nanotubes (Au-CNTs) as an Efficient Catalyst for p-Nitrophenol Reduction

The current work aims to enhance the catalytic performance of gold nanopar-ticle–carbon nanotube (Au-CNT) composites towards the reduction of p-nitrophenol. The synthesis of Au-CNT has received extensive attention because of their high stability and catalytic efficiency, particularly as a heterogeneous catalyst in the reduction of p-nitrophenol (p-NP) to p-aminophenol (p-AP) However, most of the Au-CNT preparation processes reported in the literature are time-consuming or require expensive instrumentation. In the present work, Au-CNT catalysts were synthesized via a straightforward, low-cost deposition–precipitation (DP) method. The aim of the study was to evaluate the effect of pH and aging time on catalytic activity of Au-CNTs catalyst. The Au-CNT nanocomposite catalysts were synthesized using a simple deposition–precipitation method and characterized by Brunauer–Emmett–Teller analysis, fourier transform infrared spectroscopy, atomic absorption spectroscopy, thermogravimetric analysis, field emission scanning electron microscopy, and trans-mission electron microscopy. The particle size and the loading of Au nanoparticles on the CNTs can be easily controlled by varying the pH and aging time during the synthesis process. The nanocomposite catalysts exhibited excellent catalytic activity for the reduction of p-nitrophenol to p-aminophenol in the presence of excess sodium borohydride (NaBH4). The highest rate constant (k) achieved based on the pseudo-first-order kinetic model was 1.2 × 10-3 s-1. This study offers a simple and cost-effective route to synthesize Au-CNT catalysts with high stability and catalytic efficiency for large-scale applica-tions.