# Nanoporous Au Behavior in Methyl Orange Solutions

## TL;DR

This study explores how nanoporous gold interacts with methyl orange dye in water, finding that adsorption is more significant than catalytic degradation.

## Contribution

The study provides new insights into the adsorption and catalytic behavior of nanoporous gold in methyl orange solutions.

## Key findings

- Nanoporous gold primarily adsorbs methyl orange in a partially reversible manner.
- Catalytic degradation of methyl orange occurs but is slower and less dominant.
- XPS and electrochemical analysis confirmed structural and electrochemical changes post-immersion.

## Abstract

Nanoporous (NP) gold, the most extensively studied and efficient NP metal, possesses exceptional properties that make it highly attractive for advanced technological applications. Notably, its remarkable catalytic properties in various significant reactions hold enormous potential. However, the exploration of its catalytic activity in the degradation of water pollutants remains limited. Nevertheless, previous research has reported the catalytic activity of NP Au in the degradation of methyl orange (MO), a toxic azo dye commonly found in water. This study aims to investigate the behavior of nanoporous gold in MO solutions using UV-Vis absorption spectroscopy and high-performance liquid chromatography. The NP Au was prepared by chemical removal of silver atoms of an AuAg precursor alloy prepared by ball milling. Immersion tests were conducted on both pellets and powders of NP Au, followed by examination of the residual solutions. Additionally, X-ray photoelectron spectroscopy and electrochemical impedance measurements were employed to analyze NP Au after the tests. The findings reveal that the predominant and faster process involves the partially reversible adsorption of MO onto NP Au, while the catalytic degradation of the dye plays a secondary and slower role in this system.