Electrocatalytic Oxidation of Nitrophenols via Ag Nanoparticles Supported on Citric-Acid-Modified Polyaniline

Citric-acid-modified polyaniline (P-CA) and P-CA modified with Ag nanoparticles (Ag@P-CA) were prepared via an in situ reduction method. The physicochemical properties of P-CA and Ag@P-CA were compared to unmodified polyaniline (PANI) and PANI-modified Ag nanoparticles (Ag@PANI). Ag@P-CA had a lower content of aniline oligomers compared to Ag@PANI. P-CA and Ag@P-CA had a greater monolayer adsorption capacity for 2-nitrophenol and lower binding affinity as compared to PANI and Ag@PANI materials. X-ray photoelectron spectroscopy and cyclic voltammetry characterization provided reason and evidence for the higher conductivity of citric-acid-modified materials (P-CA and Ag@P-CA versus PANI and Ag@PANI). These results showed the potential utility for the optimization of adsorption/desorption and electron transfer steps during the electrochemical oxidation of nitrophenols. The oxidation process employs Ag@P-CA as the electrocatalyst by modifying polyaniline with Ag nanoparticles and citric acid, which was successfully employed to oxidize 2-nitrophenol and 4-nitrophenol with comparable selectivity and sensitivity to their relative concentrations. This work is envisaged to contribute significantly to the selective conversion of nitrophenols and electrocatalytic remediation of such waterborne contaminants.