Abstract

Deep concerns about the hazards to human health posed by the misuse of Hg2+ constitute a considerable scientific challenge. To address these concerns, we coated electrospun carbon nanofibers (CNFs) with petal-like MoS2 grown and followed this with a facile hydrothermal treatment using thiourea (TA), thioacetamide (TAA), or l-cysteine (L-Cys) as sulfur precursors. The proposed MoS2-TA-CNF screen-printed carbon electrode (SPE) showed excellent electrocatalytic performance for the electrochemical detection of mercury ions (Hg2+) and hydrogen evolution reaction (HER) applications in acidic medium. Interestingly, MoS2-TA-CNFs have inherent electrocatalytic behavior and lower charge transfer kinetics (Rct = 46 Ω), higher anodic signal intensities, and lower anodic signal potentials than MoS2-L-Cys–CNF–SPEs or MoS2-TAA–CNF–SPEs. The proposed electrocatalyst had an ultra-low detection limit (0.16 nM) and a linear range of 5–125 nM with excellent sensitivity (4.152 μA nM-1 cm-2) for the one-step detection of Hg2+. Furthermore, square wave voltammetry (SWV) showed the anodic peak of Hg2+ was at 0.04 V (vs. Ag/AgCl). The practicability of the designed sensor was confirmed by on-site Hg2+ monitoring in samples of river, sea, and industrial water and provided satisfactory recoveries from 86.6% to 110.9% with RSDs below 5% as determined by ICP-OES. Furthermore, optimized MoS2-TA–CNF–SPEs had a low overpotential of only 146 mV and achieved at10 mA/cm2, a Tafel slope of 72.4 mV/dec, and better electron transfer resistance in HER than MoS2-L-Cys-CNF or MoS2-TAA–CNF–SPEs in acidic media over 25 h. The devised bifunctional electrocatalyst provides a unique novel means of rapidly monitoring Hg2+ concentrations in water and conducting hydrogen evolution reactions as alternatives to noble metal-based electrocatalysts.

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