Study On Electrochemical Detection Of Heavy Metal Ions In Water Based On Vanadium-based Nanomaterials

With the rapid development of industry and agriculture,people’s social level is constantly improving,and the consequent environmental problems are gradually becoming serious.Heavy metal pollution is one of the most worrying environmental problems.Especially because of the toxicity,prevalence and persistence of these substances.Since heavy metals are not biodegradable,they are harmful not only to water,air and soil,but also to human health,even in trace amounts.Therefore,there is an urgent need to develop a stable,efficient,economical and rapid analytical method that can be applied to a wide range of conditions and can accurately and sensitively detect heavy metal ions.Electrochemical analysis method is considered to be the most promising method for scaled-up heavy metal detection due to its unique advantages,and the key to this method is the construction of electrode sensing interface.In recent years,nano-transition metal oxide materials have been widely studied because of their abundant reserves and remarkable activity.However,simple metal oxides inevitably face the problem of agglomeration and low electrical conductivity.Therefore,vanadium-based nanomaterials combined with reactive transition metal composites were investigated for their morphological structures and detection properties,respectively.The research in this paper is carried out in the following aspects:（1）The pod-shaped Fe₂VO₄/NC nanowires were obtained by calcination of polydopamine-coated FeVO₄·1.1H₂O nanowires,which were modified at the glassy carbon electrode to achieve sensitive detection of Pb（Ⅱ）by anodic square wave voltammetry.The adsorption experiments confirmed that the Fe₂VO₄ nanowires with nitrogen-doped carbon shells showed the strongest adsorption of Pb（Ⅱ）.In addition,the bimetallic synergy of Fe（Ⅱ）and V（Ⅳ）provides the driving force for the redox of heavy metal ions.The Fe₂VO₄/NC with internal space has more active sites and faster ion transfer rate than bare nanowires,which improves the poor conductivity of metal oxides alone.Finally,the stability,reproducibility,and interference resistance of the experiments were evaluated and successfully applied to the detection of real water environments.（2）Based on the bimetallic synergy,we chose to combine vanadate with the active metal Co to construct a synergistic working hybrid system.Co₂VO₄ nanosheet-loaded Co（0）composites were obtained after calcination of the precursor Co₂V₂O₇-x H₂O nanosheets under H2/Ar atmosphere.The sensitive electrochemical analysis of Hg（Ⅱ）was achieved with a detection sensitivity of 1943.2μA·μM^-1·cm^-2 and a theoretical detection limit of 0.027μM.HRTEM data showed that the loading of Co（0）avoided the close stacking of nanosheets,which allowed the existence of gaps between the layers and provided more active area and sites.Meanwhile,the reason for the increased sensitivity of Co/Co₂VO₄ to Hg（Ⅱ）was analyzed in conjunction with the X-ray photoelectron spectroscopy adsorption data.In addition,the stability,reproducibility,and resistance to interference from other heavy metals of the constructed sensitive interface make the electrode of good practical value.This work provides a promising strategy to improve the performance of metal oxides for the detection of heavy metal ions.