Fabrication Of Micro-nanoporous Silver And Copper By Oxidation And Reduction And Its Application

Micro-nano porous metals are composed of metallic material skeleton and porous structure,which have good electrical conductivity,larger surface area and excellent catalytic performance.They are widely used in Raman enhancement,energy materials,catalysis and drug detection.However,at present,the preparation methods of micro-nano porous metals mainly including dealloying method and template method.Furthermore,their applications in various fields need to be further studied.Thus,in this thesis metallic silver and copper were selected,A oxidation-reduction technology was developed for the fabrication of micro/nano porous metal,The obtained micro/nano porous silver was applied for the Raman enhancement.Whereas,the micro/nano fiber copper was used in water electrolysis reaction.The research enrichs the fabrication strategy of micro-nano porous metal and expand their wide application range.In the preparation of micro-nano porous silver,commercial silver wire(diameter of 300?m)was used as the initial material,and the micro-nano porous structure was created on its surface by electrochemical oxidation and subsequent solution reduction.By changing the experimental parameters(mainly electrochemical oxidation conditions),the pore structure was tuned.The obtained results indicate that the optimal treatment condition of the silver wire is oxidized for 9 min under 10m A cm^-2 and then reduced in sodium borohydride solution.Under these conditions,the particle size of porous silver wire was the smallest(?180nm),and the pore structure was evenly distributed.When it was used as a probe in SERS,the enhancement factor in 10^-6M crystal violet reached4.97×10⁶.In the preparation of micro and nano fiber copper,commercial copper foam was used as the initial material and ammonium persulfate was used as the oxidant to obtain the copper oxide foam with needle-like structure.The prepared copper oxide foam was used as the self-supporting electrode for electrochemical water electrolysis.The catalytic performance of the electrode for HER and OER were characterized.The oxidized copper foam obtained after 160min oxidation shows the best performance,with the largest specific surface area and the smallest HER and OER overpotential(241m V and 365m V,respectively).The oxidized precursor was reduced by Dimethylamine-Borane(DMAB)to obtain micro-nano fiber copper.The effects of different oxidation time on the microstructure and electrochemical properties were studied.Among them,after oxidation for 160min and subsequent reduction,the HER and OER of the electrode exhibit the smallest overpotential(183.61m V and 123.68m V).Compared with the overpotential of HER(524.44m V)and OER(459.6m V)of untreated copper foam,oxidation and redox treatment could be considered as effective approaches to enhance the electrochemical performance of copper foam.In order to investigate the effect of microstructure of precursors on the obtained fiber profiles and corresponding electrochemical performance.commercial copper foil with the thickness of 35?m was also used as the initial material.The micro-nano-fiber copper was prepared under the same solution oxidation-reduction method.The formed micro-nano fiber layer seems more robust and the corresponding electrochemical performance is more stable.After 24h stability test,the increase for overpotential was only 19 m V.