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Constructing low cost and efficient electrochemical sensors for highly sensitive detection of hydrazine has a great significance in the field of environmental monitoring and protection. Herein, metal–organic framework derived Co3S4 nanosheets grown on Ti mesh (Co3S4/TM) were successfully synthesized by employing a facile anion exchange reaction and hydrothermal vulcanization with Co-MOF as the precursor. The crystalline structure and morphology of as-synthesized samples were characterized by XRD, SEM, Raman, XPS and TEM analysis. It was found that Co3S4 nanosheets were stacked loosely and irregularly on each other to form a three-dimensional (3D) porous structure. The electrochemical sensing performance of Co3S4/TM toward hydrazine was investigated in 0.1 M NaOH solution. The results showed that Co3S4/TM presented a better electrocatalytic activity toward hydrazine oxidation than Co-MOF/TM and Co(OH)2/TM, owing to the high electrical conductivity of Co3S4 for enhancing electron transfer and the 3D porous structure for providing many more accessible active sites and shortening ion diffusion length as well as promoting mass transfer for hydrazine electrooxidation. As a result, Co3S4/TM exhibited a superior analytical performance with a wide linear range of 0.005–2.0 mM, a high sensitivity of 2956 μA mM−1 cm−2 and a low detection limit of 0.7 μM (S/N = 3), which was superior or comparable to that of the recently reported sensor. Because of the good selectivity and reproducibility, Co3S4/TM was applied to detection of hydrazine in tap water and it showed good recovery, indicating that it could be a promising candidate for analyzing hydrazine in practical application. [ABSTRACT FROM AUTHOR]

Exploiting cost-effective, highly efficient and stable alkaline electrocatalysts is a great challenge for the hydrogen evolution reaction (HER). Herein, NiMoO4 and CoFe layered double hydroxide (CoFe LDH) with poor crystallinity were successively deposited on Cu nanowire (Cu NW) grown on Cu foam by a two-step electrodeposition process, which was verified by XRD, Raman, ATR-FTIR, XPS, SEM, TEM and HRTEM characterizations. The HER performance measurement in 1.0 M KOH solution showed the optimal CoFe LDH-60 s/NiMoO4/Cu NW/Cu foam sample demonstrated prominent alkaline HER activity and long-term durability with an ultralow overpotential of 45 mV at −10 mA cm−2 and a Tafel slope of 94.0 mV dec−1, superior to the recently reported transition metal-based electrocatalysts. Further study clarified that the remarkable alkaline HER performance could be attributed to the strong synergistic effect between CoFe LDH-60 s and NiMoO4 in favor of water adsorption/activation and optimizing hydrogen adsorption, and providing plentiful exposed active sites as well as an enhanced electron transfer process offered by the unique 1D nanostructure with Cu nanowire as the core. This work can provide a guidance for designing a highly active and stable electrocatalyst for hydrogen production. [ABSTRACT FROM AUTHOR]

Three-dimensional interconnected Co(OH)2 nanosheets (Co(OH)2 NS) were electrodeposited onto a Ti mesh (TM) surface, which was demonstrated by XRD, Raman spectroscopy, XPS and SEM characterization. The electrochemical sensing performance of the Co(OH)2 NS/TM toward hydrazine was investigated by cyclic voltammetry and amperometric techniques in a 0.1 M NaOH aqueous solution. The as-prepared Co(OH)2 NS/TM with an electrodeposition time of 10 min exhibited prominent capacity to detect hydrazine with a wide linear range from 5 μM to 3.0 mM and limit of detection (LOD) of 1.98 μM. Co(OH)2 NS/TM electrodes also showed a high sensitivity of 2793.9 μA mM−1 cm−2, excellent selectivity, reproducibility, appreciable stability with a RSD less than 3.5%, as well as the high recovery of hydrazine in real samples, indicating its potential application in real sample analysis. [ABSTRACT FROM AUTHOR]