Synergistic Carbon Black-Supported Nickel-Iron Hydroxide Nanocomposite for Selective Electrochemical Discrimination of Dihydroxybenzene Isomers

Abstract

Detection and simultaneous discrimination of dihydroxybenzene (DHB) isomers, particularly catechol (CT) and hydroquinone (HQ), remain challenging due to their closely similar electrochemical responses and partially overlapping redox potentials. These difficulties become more pronounced in binary mixtures, where signal interference complicates analysis across wide concentration ranges. In this work, we report a carbon black-supported nickel-iron hydroxide nanocomposite as a low-cost, non-enzymatic electrochemical sensing material operating at neutral pH, implemented on both conventional electrodes and disposable strip sensors. The optimized sensor showed clear peak separation for CT and HQ, including in equimolar (1:1) mixtures, and achieved limits of detection down to 0.01 micromolar on the glassy carbon platform and 0.05 micromolar on the strip sensor. The sensing platform also showed excellent repeatability over more than 5000 continuous measurements and strong reproducibility over extended time intervals. In addition, statistical descriptors of the voltammetric responses, including skewness and kurtosis, are used as complementary tools to analyze concentration-dependent signal variations. Physicochemical characterization of the nanocomposite supports the proposed interpretation of the observed electrocatalytic performance.