DOI: https://doi.org/10.55373/mjchem.v27i3.173

Keywords: Anodic aluminum oxide (AAO); gold nanoparticles (Au NPs); deposition-precipitation (DP); p-nitrophenol; catalytic activity

Abstract

Anodic aluminum oxide (AAO) has emerged as a robust catalyst support due to its superior mechanical properties and thermal stability. Fabricated through a two-step electrochemical anodization process, AAO can be tailored into membrane and wire forms, offering control over pore size, alignment, and thickness by adjusting anodization parameters such as voltage and electrolytes. While AAO membranes have been extensively studied, the potential of AAO wires as catalyst support remains under-explored. This study aims to evaluate the catalytic performance of AAO in both membranes and wires form as supports for gold nanoparticles (Au NPs) in the reduction of p-nitrophenol (p-NP). AAO membrane (mAAO) and wire (wAAO) were fabricated under similar anodization parameters and immobilized with Au NPs via deposition-precipitation (DP) technique yielding Au/mAAO and Au/wAAO catalysts. Characterization by Fourier Transform Infrared Spectroscopy (FTIR) confirmed successful Au immobilization with notable shifts in the O-H bond (~3400 cm^-1) and Si-O bond (~1000 cm^-1). Field-Emission Scanning Electron Microscopy (FE-SEM) further demonstrated uniform pore distribution of AAO and well-dispersed Au NPs yielding values of 76.75 ± 11.29 nm and 16.03 ± 5.54 nm for Au/mAAO while for Au/wAAO are 74.97 ± 10.49 nm and 18.43 ± 11.16 nm, respectively. Additionally, the XRD instrument was utilized to investigate the amorphous patterns and nanocrystalline properties of the modified AAO forms. The % Au loadings show the value of 0.88 wt% (Au/mAAO) and 0.92 wt% (Au/wAAO). Catalytic activity was assessed via Ultraviolet-Visible Spectroscopy (UV-Vis) revealed that Au/mAAO exhibited significantly higher rate constants (k = 4.24 × 10-3 s^-1) compared to Au/wAAO (k = 4.31 × 10-4 s^-1) highlighting the superior performance of the membrane form.