Effect of silver addition on the structure of microwave-synthesized CuAg solid solutions for organic pollutant degradation

Abstract

This study reports the one-pot microwave synthesis of Cu-Ag powders with varying copper-to-silver molar ratios (10:1, 5:1, 2:1, and 1:1) via the reduction of copper and silver salts using ascorbic acid. The resulting products were systematically analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and electrical resistivity measurements. XRD results reveal the coexistence of Cu-rich Cu(Ag) and Ag-rich Ag(Cu) solid solutions, with the weight fraction of Cu(Ag) decreasing as Ag content increases. The crystallite size ranges from 82 to 231 nm. Increasing Ag content disrupts the Cu lattice, enhances electron scattering, and reduces charge carrier mobility, leading to a significant increase in electrical resistivity, with ρ= 3.14 Ω·cm for CuAg10/1 and 6.71 Ω·cm for CuAg1/1. The solid solutions display an oxidizing property in aqueous medium, which diminishes as Ag content increases. The oxidation of Methylene Blue (MB), used as a test molecule, occurs via an indirect process where the powder generates hydroxyl radicals in the acidic medium. Complete degradation of MB with CuAg 10/1 occurs within 25 min using 30 mg of the powder at 60 °C and pH 3. The processing time is further reduced to 6 min when the degradation is conducted under microwave irradiation.