The present work reports on electrocatalytic activity of silver electrode for 4-nitroaniline (4-NA) reduction, where its performance is compared with conventionally used electrodes (gold, graphite and glassy carbon). The voltammetric behavior of 4-nitroaniline (4-NA) is explored where a sensitive cathodic peak has appeared at about ? 0.26 V (vs. Ag/AgCl/3 M KCl) in Britton Robinson buffer solution (pH 2.0). This peak results from the irreversible reduction of 4-NA at metallic silver electrode. The catalytic effect was evaluated using cyclic voltammetry and chronoamperometry. Indeed, the cathodic transfer coefficient was 0.57 and electron transfer rate constant was evaluated to be 7.38 × 10? 5 cm2 s? 1. Electrochemical impedance spectroscopy also confirms our experimental results as the silver electrode shows least charge transfer resistance. In order to provide electrochemical detection to reducing the nitro groups of 4-NA on the silver electrode surface, the differential pulse voltammograms were used in the potential range between 0.2 V and ? 1 V vs. Ag/AgCl/(sat. KCl).
Furthermore, silver electrode can be used successfully to improve the detection of 4-NA at very low concentration levels with high sensitivity. The linear calibration range was from 8.0 × 10? 9 to 1.0 × 10? 3 mol L? 1. The limit of detection (LOD) was found to be 4.74 × 10? 9 mol L? 1, while relative standard deviation (RSD) at 1.0 × 10? 4 mol L? 1 4-NA concentration was 1.94% for eight repetitions. Then, the proposed method was applied to detect 4-NA in wastewater and drinking water with satisfactory results.
