Interface Engineering of Mos2 Nanopetal Grown on Carbon Nanofibers for the Electrocatalytic Sensing of Mercury (Ii) and Efficient Hydrogen Evolution

Abstract

Deep concerns about the hazards to human health posed by the misuse of Hg 2+ constitute a considerable scientific challenge. To address these concerns, we coated electrospun carbon nanofibers (CNFs) with petal-like MoS 2 grown and followed this with a facile hydrothermal treatment using thiourea (TA), thioacetamide (TAA), or l-cysteine (L-Cys) as sulfur precursors. The proposed MoS 2 -TA-CNF screen-printed carbon electrode (SPE) showed excellent electrocatalytic performance for the electrochemical detection of mercury ions (Hg 2+ ) and hydrogen evolution reaction (HER) applications in acidic medium. Interestingly, MoS 2 -TA-CNFs have inherent electrocatalytic behavior and lower charge transfer kinetics (R ct  = 46 Ω), higher anodic signal intensities, and lower anodic signal potentials than MoS 2 -L-Cys-CNF-SPEs or MoS 2 -TAA-CNF-SPEs. The proposed electrocatalyst had an ultra-low detection limit (0.16 nM) and a linear range of 5 to 30 nM with excellent sensitivity (11.385 µA nM -1  cm -2 ) for the one-step detection of Hg 2+ . Furthermore, square wave voltammetry (SWV) showed the anodic peak of Hg 2+ was at 0.04 V (vs. Ag/AgCl). The fabricated sensor was also found to be exhibit excellent repeatability (2.8%), reproducibility (3.2%), renewability (92.6%), stability (88.72%) (after storage for 30 days), and was relatively unaffected by organic and inorganic interfering species in terms of sensing Hg 2+ . 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 MoS 2 -TA-CNF-SPEs had a low overpotential of only 146 mV and achieved  at10 mA cm -2 , a Tafel slope of 72.4 mV dec -1 , and better electron transfer resistance in HER than MoS 2 -L-Cys-CNF or MoS 2 -TAA-CNF-SPEs in acidic media over 25 h. The devised bifunctional electrocatalyst provides a unique novel means of rapidly monitoring Hg 2+ concentrations in water and conducting hydrogen evolution reactions as alternatives to noble metal-based electrocatalysts.

Keywords: Mercury ion, MoS2, Carbon nanofibers, Square-wave voltammetry, Electrochemical sensor, Hydrogen evolution