Two-dimensional Ni/Co bimetal pyrophosphate nanosheets for sensitive electrochemical detection of phenol

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As a priority pollutant in many regions, phenol in environment may cause severe damage to human health and ecosystem. For the simultaneous detection of phenol in environment, a novel electrochemical sensor has been constructed in this work based on the 2D nickel cobalt pyrophosphate (denoted as NCppi) nanosheets modified glass carbon electrode (GCE). The nickel cobalt pyrophosphate was prepared by a facile hydrothermal method. The prepared 2D nickel cobalt pyrophosphate nanosheet was characterized by X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy. The bimetal nickel cobalt pyrophosphate exhibited favorable catalytic activity in phenol detection. The excellent sensing performance of nickel cobalt pyrophosphate was attributed to its charge transfer mobility and abundant catalytic sites. The nickel cobalt bimetal pyrophosphate was applied to modify glass carbon electrode (denoted as NCppi/GCE) and the obtained sensor processed satisfactory analytic performance in practical detection of phenol. Cyclic voltammetry (CV) was employed to characterize electrochemical behavior of modified GCE and bare GCE in 100 μM phenol solution. Electrochemical impedance spectroscopy (EIS) and CV were employed to characterize the charge transfer process and redox nature of different electrodes in 4 mM Fe(CN)63-/4- containing 0.1 M KCl. Square wave voltammetry (SWV) was employed to detect phenol in 0.2 M phosphate buffer solution (pH=7.0). The fabricated electrochemical sensor with optimized Ni/Co ratio also exhibited a limit of detection (LOD) of 0.25 μM, a limit of qualification (LOQ) of 0.45 μM and a linear range of 0.5–100 μM with a sensitivity of 0.0269 μA/μM using square wave voltammetry (SWV) toward phenol. Besides, the electrochemical sensor showed desirable selectivity. In standard addition test of tap water sample from Longwangzui Water Plant and river water from Xunsi River, the sensor displayed reliable recoveries. The electrochemical sensor still maintained 87.5% current response after 3-week storage. The GCE was 50 $ and the cost of catalytic ink could be ignored. The active surface area of NCppi/GCE was 0.12 cm2.