Synthesis of Au-Cu/AAO catalyst for p-nitrophenol reduction / Nurul Afifah Ramli

Gold-copper (Au-Cu) bimetallic catalysts were prepared via chemical reduction with Cu and Au precursors and hexadecylamine (HDA) as the capping agent to form Au-Cu bimetallic nanoparticles (Au-Cu NPs). The colloidal Au-Cu NPs were subsequently spin-coated onto an anodic aluminium oxide (AAO) support. The AAO support was fabricated via a two-step anodization technique at 80 V using oxalic acid as an electrolyte. The bimetallic catalysts outperformed monometallic Au and Cu NPs in terms of activity towards reducing p-nitrophenol (p-NP). The optimized Au-Cu/AAO catalyst exhibited 100% p-NP conversion to p-aminophenol (p-AP), demonstrating its capability in pollution treatment and chemical synthesis. Furthermore, the AAO membrane support made it simple to recover and reuse the catalyst, supporting long-term stability and sustainability. The highest rate constant (k) of 1.2x10-3 s-1 was achieved over 1 mg of Au-Cu/AAO catalyst. The k value for Au/AAO, and Cu/AAO is 1.0x10-4 s-1, and 8x10-5 s-1 respectively. Meanwhile, the k value for reused catalysts of Au-Cu/AAO, and Au/AAO is 3.0x10-5 s-1 and 8.0x10-5 s-1, respectively. However, the reused catalyst of Cu/AAO showed no p-NP reduction. Fourier Transform Infrared (FTIR) spectroscopy, Inductive Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) and Field Emission Scanning Electron Microscopy (FESEM) were used to characterize the synthesized catalysts, and an Ultraviolet-Visible (UV-Vis) spectrophotometer was used to monitor the catalytic investigation.