Reliable electroanalysis of Hg(II) in water via flower-like porous MnCo2O4: Excellent multilayer adsorption and (Mn, Co)(II)/(Mn, Co)(III) cycles

Abstract

Constructing an electrochemical sensing interface with high sensitivity and revealing its sensitive mechanism is of great significance for the reliable determination of trace Hg(II) in water. In this work, flower-like porous MnCo2O4 nanomaterial was prepared and applied as an electrode modifier to detect Hg(II). The obtained sensitivity and limit of detection were 70.679 μA μM−1 and 0.004 μM, respectively. Meanwhile, the possible reasons for enhancing the stripping signal of Hg(II) were investigated by combining adsorption isotherms, electrochemical experiments, X-ray photoelectron spectroscopy (XPS) tests, etc. These results showed that the flower-like porous MnCo2O4 nanomaterial has a high and multilayer adsorption of Hg(II), and then Hg(II) readily diffuses from the outer surface of the MnCo2O4 to the electrode surface, so that more Hg(II) redox reactions occur. Besides, the (Mn, Co)(II)/(Mn, Co)(III) cycles were found to be an essential factor for promoting the redox reaction and improving the electrochemical signal of Hg(II). The electrochemical sensing interface possesses high anti-interference ability, excellent stability and reproducibility. Significantly, this electrochemical sensor obtained accurate result for the analysis of Hg(II) in real water samples. These findings provide new insights into designing superior electrode modifiers and understanding the sensitive mechanisms that improve electrochemical signals.