Modification Of Ti Substrates By Chemical Deposition And Their Applications In Pollutant Degradation And Raman Analysis

Mineralizing organic pollutants by electrocatalytic advanced oxidation technology（AEOP）is a promising wastewater treatment technology.However,the current anodes for electrocatalytic oxidation has actual problems such as high preparation cost,insufficient catalytic efficiency and short service life,cannot be widely used.This research aimed to solve those problems so that electrocatalytic oxidation technology can take a small step towards industrialization.Theoretically,chemical deposition technology can achieve perfert deposition without missing corners.This structure has fewer defect areas than films prepared by other methods.It implies that the electrode materials obtained by chemical deposition has longer service life.Ti metal gets a good electrical conductivity and can self-form a thin layer of metal oxide film.Self-generated Ti oxide has excellent acid and alkali resistance.Cu metal has excellent catalytic activity,and the doping of Cu oxide can greatly increase the oxygen evolution potential（OEP）of the tin-antimony oxide electrode and catalytic efficiency of producing active oxygen species.Finally,we chose the chemical deposition technology to prepare an active anode co-doped with three elements of copper,tin and antimony on the titanium surface,and utilized it to the complete mineralization of refractory organics.Ti metal can generate strongly reducing Ti³⁺in an acidic solution containing fluoride ions.The trivalent Ti³⁺can reduce the metal ions in the solution.Reduced metal ions form nanoparticle and deposit on the Ti surface.The controllable deposition of multiple metal elements can be realized by slightly adjusting the reaction conditions.Since the structural features of metal Au,Ag,and Cu deposited on the Ti surface are same to the materials with strong surface plasmon resonance（SPR）.We use finite difference time domain（FDTD）theoretical simulation and actual surface enhanced Raman（SERS）test to evaluate SERS substrates’performance.Finally,the Ti-based multi-layer Ag SERS substrate with strong Raman activity was prepared and applied to the detection of uric acid molecules and explosive molecules The specific research topics are as following:1.This work prepared a CuO-SnO₂-SbO_X electrode on Ti substrate,which is achieved by ultrasonic assisted deposition of Cu layer,followed by electroless deposition of Sn-Sb layer and finalized by calcination at 500°C.The obtained electrode（Ti/CuO-SnO₂–SbO_X）exhibited high catalytic degradation activity and a high oxygen evolution potential（OEP）of 2.13V,which is0.4 V greater than that of the widely recognized Ti/SnO₂–SbO_X electrode.The oxygen evolution reaction（OER）models of active oxygen intermediate adsorption were optimized by density functional theory（DFT）calculations.The results revealed that（1）theΔG of the OER rate-determining step was raised to 2.30 e V after Cu doping on 101 plane;（2）binding energies of the optimized surface with reactive oxygen species（ROS）were substantially decreased.Furthermore,the as-prepared electrode has a high yield of hydroxyl radical generation as evidenced by terephthalic acid detection.The potential for hydroxyl radical generation was measured to be 1.8 V at p H=12 and 2.6 V at p H=2.The catalytic degradation rate of methylene blue（MB）follows pseudo first order reaction kinetics,and the reaction constant K value reached0.02964-k/min^-1,twice as much as that obtained from electrodeposition electrode（Ti/Cu/SnO₂–SbO_X）.A degradation rate of 94.6%was achieved for MB in 100 min in the first run,and the value remained over 85%in the subsequent 10 runs.At the same conditions,the degradation rate of p-nitrophenol was over 90%in 100 min and complete mineralization was achieved in 4h.2.Development process of SERS substrate was guided by the result of FDTD simulation,which estimated the amount of electromagnetic field enhancement causing by various scale and element of materials.Finally,‘Ag-Ag’gaps with higher electromagnetic field enhancement was selected to replace‘Ag-Ti’gap substrates and the scale of AgNPs were fixed into 100 nm.In order to turn theory into a reality model,a multilayered Ag nanoparticles SERS substrate was prepared by a two-step electroless deposition of Ag（or other coinage metals）on Ti substrate.Subsequently form a Ag nanoflake（AgNF）layer and a Ag nanoparticle（AgNPs）layer on the Ti base（Ti/AgNFs/AgNPs）.Meanwhile,AgNPs with multi-morphologies and sizes can be readily prepared by tuning the reaction conditions.The As-prepared SERS substrate showed an enhanced SERs effect for small molecule detection and a detection limit as low as1.0×10^-12 M for picric acid（PA）and 1.0×10^-6 M for uric acid（UA）was obtained respectively,which are substantially lower than that of literature values.The signal of UA in human urine can be clearly detected.Compare the actual spectrum of PA with the simulated spectrum by DFT method,and interpret its Raman spectrum information.The facile and convenient preparation method presented in this work should be widely applicable for in-situ preparation of other SERs substrates.