Detection Of Lead Ions In Wastewater By Preparing Palladium Nickel Nanomaterials

Electrochemical detection of heavy metal ions has received wide attention due to its high sensitivity,good selectivity and low cost.Here,it is proposed to construct a nanomaterial electrochemical sensor to detect Pb²⁺ions.The preparation of nanomaterials and sensor performance testing are the main research contents.A series of Pd core nickel oxide/hydroxide?NiO_xH_y?doped PdO shell?Pd@PdO-NiO_xH_y?composite nanoparticles supported on activated carbon?Pd@PdO-NiO_xH_y/C?are synthesized under a vacuum degree of-0.07 MPa by heat-treating the Pd₂-Ni₁/C nanomaterials,which was prepared using a solvothermal process.The TEM results show that the Pd@PdO-NiO_xH_y nanoparticles are uniformly dispersed on the carbon support,and the HRTEM result prove that the shell of the Pd@PdO-NiO_xH_y nanoparticle was the NiO_xH_y doped PdO.The actual Pd loading measured by ICP for the Pd@PdO-NiO_xH_y/C nanomaterials prepared at 300°C and 400°C is about 16%,which is close to that of the Pd₂-Ni₁/C.The XRD and the XPS analysis reveal that the nanomaterials exhibites a core-shell structure with a Pd core and a PdO metal oxide layer doped by NiO_xH_y?NiO,Ni?OH?₂,NiOOH,Ni₂O₃?.Cyclic voltammetry?CV?,chronoamperometry and electrochemical impedance spectroscopy?EIS?are employed to study the electrochemical performance of the Pd@PdO-NiO_xH_y/C nanomaterials.The results show that Pd@PdO-NiO_xH_y/C prepare at 400°C?Pd@PdO-NiO_xH_y/C-400?have the best catalytic activity and stability in all nanomaterials.The mass peak current density of the Pd@PdO-NiO_xH_y/C-400 for the methanol electrooxidation is 930.1 mA mg^-11 Pd,which is 2.1 and 1.5 times higher than those of the Pd/C?449.3 mA mg^-11 Pd?and Pd₂-Ni₁/C(632.0 mA mg^-1Pd),respectively.This improvement is attributed to the unique structure of the NiO_xH_y doped PdO shell layer of the Pd@PdO-NiO_xH_y nanoparticles in the Pd@PdO-NiO_xH_y/C-400,which enhances the active surface area of the nanomaterial.Moreover,PdO and NiO_xH_y on the surface provide more binding sites for the intermediate products OH and OOH produced during the methanol electrooxidation,improving the reaction kinetics.In addition,the mass peak current density of the Pd@PdO-NiO_xH_y/C-400 for the electrooxidation ethanol is2175.9 mA mg^-11 Pd,which is about 4.1 times as high as that of the Pd/C?533.2mA mg^-11 Pd?.The obtained Pd@PdO-NiO_xH_y/C-400 nanomaterial is used to modify the glass carbon electrode to detect the Pb²⁺by cyclic voltammetry and compared with the Pd/C nanomaterial.For Pd@PdO-NiO_xH_y/C-400 nanomaterial,the Pb²⁺detection limit is 0.2¹2.11 mM,higher than 0.5⁸.49 mM of the Pd/C.In addition,Pd@PdO-NiO_xH_y/C-400 nanomaterial modified electrodes exhibit excellent anti-interference and reproducibility,and when 10 times of interference ions were added,the variation of CV current of Pd@PdO-NiO_xH_y/C-400 is less than 20%.This increase of Pd@PdO-NiO_xH_y/C-400 in sensitivity and anti-interference capability is attributed to unique surface structure and electron synergy for the improvement of the surface area and stability of the material.