Preparation Of Nickel Nanorod Arrays Electrode And Their Application In Electrochemical Oxidation Reaction

With the rapid deterioration in the environment and the continuous exhaustion of fossil fuels worldwide,there is an urgent need for early detection and treatment of pollutants and the development and usage of clean renewable energy.Electrochemical oxidation plays an important role in these two aspects and excellent electrode materials are the core elements for both organic pollutant detection/degradation and electrocatalytic oxygen evolution reaction（OER）applications.Nickel（Ni）-based active materials are one of the most promising materials for electrochemical oxidation due to properties such as their low cost,abundant availability,electrochemical oxidation resistance,and excellent electrical conductivity.Unfortunately,the application performance of most Ni-based electrode materials in electrochemical oxidation processes such as the detection of organic pollutants and electrocatalytic OER remains unsatisfactory,and some important problems need to be addressed urgently:First,the conventional nano-powder Ni-based catalysts have an insufficient catalytic interface and limited charge conduction efficiency,significantly inhibiting the electrochemical performance;Second,the material has poor selectivity and weak response signal for trace organic pollutants in the detection process;Finally,the thermodynamic adsorption energy of Ni-based materials for OER intermediates（OH*,O*,and OOH*）is unreasonably strong or weak,which leads to higher reaction energy barrier for OER at its surface interface,resulting in insufficient catalytic activity.Therefore,it becomes imperative to develop a high-performance and multifunctional Ni-based electrode material considering different electrochemical oxidation reactions.Given the above problems,this work focused on the design and construction of a new type of high-performance Ni nanorod arrays（Ni-NRAs）electrode and its application in the detection of organic pollutants and the electrocatalytic OER process.The main study highlights are:（1）Preparation and modification of large-size self-supporting Ni-NRAs.Ni-NRAs electrode with large size,high specific surface area,and high conductivity was successfully fabricated via electroplating with a nanostructured Si template-assisted strategy.The electrochemical test and microstructure analysis demonstrated that the nanowire array structure significantly increased specific surface area and charge transfer efficiency of different Ni-based materials,remarkably enhancing their electrochemical activity.The surface of Ni-NRAs electrode could be highly modified by N₂and N₂O plasma treatment,the number of active sites for electrochemical oxidation of Ni-NRAs electrode after modification significantly increased,resulting in improved electrocatalytic performance of OER.This was attributed to the presence of active components（Ni O_xand Ni_xN）on the surface of the Ni-NRAs electrode after plasma treatment by X-ray photoelectron spectroscopy（XPS）.（2）A molecular-imprinted（MI）Ni-NRAs electrode（Ni-NRAs/MI-Ni Al-LDH）was constructed,and its performance for selective detection of Glyphosate（GLYP）pollutants was examined.In this work,the Ni-Al bimetallic hydroxide hydrotalcite（Ni Al-LDH）active layer was modified on the surface of the Ni-NRAs electrode to build Ni-NRAs/Ni Al-LDH electrode,which enhanced the electrochemical oxidation activity of the Ni-NRAs electrode for GLYP pollutants,and resolved the problems of its low detection sensitivity and weak detection signal for GLYP.Furthermore,the Ni-NRAs/MI-Ni Al-LDH electrode was constructed by imprinting GLYP molecular holes on the surface of the Ni-NRAs/Ni Al-LDH electrode using MI technology,which realized the highly selective detection of GLYP in the electrochemical oxidation reaction of the Ni-NRAs electrode.The oxidation current peak（I_p）was proportional to the GLYP dosage from 10.0 n M to 20.0μM;the limit of detection（LOD）was calculated to be 3.0 nmol/L（S/N=3）.Ni-NRAs/MI-Ni Al-LDH electrode exhibited excellent discriminating ability,high anti-interference capacity,and good long-term stability for GLYP electrochemical detection.（3）Efficient preparation of Ni-M（M=Fe,Co,Mo）bimetallic oxides layer on Ni-NRAs for electrocatalytic OER.Free-standing Ni/Ni-M（M=Fe,Co,Mo）bimetallic oxides core/shell nanorod arrays（Ni/Ni-M NRAs）were prepared through a combination process of electroless deposition of transition metal species on black nickel sheet（Ni-NRAs）and followed electrochemical oxidation.All three types of Ni/Ni-M NRAs showed an enhanced electrocatalytic activity towards OER.Ni/Ni-Fe NRAs electrode exhibited a small onset potential of 1.535 V at a current density of 10m A?cm^-2.For Ni/Ni-Fe NRAs,the OER current density loss was only 13.5%at a constant overpotential of 500 m V for 20,000 s while the catalytic performance of Ni/Ni-Co and Ni/Ni-Mo NRAs almost disappeared under similar conditions.These results differ from several previous reports about superior OER stability of Ni-based bimetallic catalysts.Results of correlation mechanism analysis showed that NRAs structure led to a dramatic improvement in both electrochemically active surface area（ECSA）and charge transfer rate;the transition metal dopants regulate the electronic structure of the Ni O and adjust the strength of the chemical bonds between the Ni-based catalytic interface and OER reactive intermediates（OH*and O*）to more favorable values,thereby inducing a lower energy barrier for O₂generation.