Entirely nitrate-free synthesis of silver nanoparticles via electrochemical synthesis–chemical reduction†

Among silver compounds, only silver nitrate (AgNO₃) is readily soluble in water, which has led to the dominance of nitrate systems in the chemical reduction (CR) method that utilize Ag compounds as feedstocks. During the synthesis of silver nanoparticles (Ag NPs) via the CR of AgNO₃, nitrate wastewater and nitrogen oxide pollution are generated. The nitrate-related pollution has compromised the environmental advantages of the CR method for Ag NP synthesis. In this study, we propose an electrochemical synthesis (ES)–CR method for the entirely nitrate-free synthesis of Ag NPs. In an eco-friendly acetate system, metallic silver is dissolved in the anolyte through anodic dissolution. An anion exchange membrane is employed to concentrate silver ions in the anolyte, while the cathode generates hydrogen gas. After ES, the anolyte serves as the precursor for the CR process. Ag NPs with diverse morphologies can be synthesized via CR. Unlike conventional AgNO₃-based CR, the ES–CR method excludes the use of nitrate reagents. Furthermore, it streamlines the conversion of metallic Ag to Ag NPs. The proposed ES–CR method is expected to become an environmentally sustainable alternative method for the synthesis of Ag NPs.