Interface engineering of MoS2 nanopetal grown on carbon nanofibers for the electrocatalytic sensing of mercury (II) and efficient hydrogen evolution

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.