Fabrication Of One-Dimensional Silver-Based Nanomaterials And Their Transparent Conductive Property And Catalytic Performance For Oxygen Reduction

Silver is a widely used material in electronic devices,heat dissipation and catalysis due to its excellent conductivity,heat conduction,ductility and catalytic activity.One-dimensional silver-based nanomaterials not only inherit the excellent properties of metallic silver,but also have excellent flexibility and porousity,which show great application prospects in the fields of flexible electronics and electrocatalysis.This thesis mainly studied on the preparation and properties of several different one-dimensional silver-based nanomaterials,and investigated their performances in the field of conducting film and catalytic oxygen reduction.Silver nanowires?AgNWs?with the diameter of 36 nm and length of 20?m were prepared by the polyol method and were used in transparent conductive films?TCFs?.By introducing SiO₂ nanospheres?SiO₂-NSs?into the film,the distribution and contact of AgNWs was promoted through the electrostatic interaction between them,which could decrease the sheet resistance of the conductive film from 240?/sq to 33?/sq.The introduction of SiO₂ layer also enhanced the transmission of visible light remarkably through antireflection effect,where the transmittance can be increased from 94%to 98%.Typically,a AgNW/SiO₂-NS-based TCF with a sheet resistance of ca.33?/sq and transmittance of ca.98.0%could be obtained,which can withstand 300°C heat treatment.Moreover,the electroplating process was adopted to enhance the performance of AgNWs-based TCFs.The sheet resistance of conductive film could be reduced from 180?/sq to 9.8?/sq through the bridging of electoplated metals between the AgNWs.With the assistance of a rotating magnetic field,nickel films were formed on both sides of the silver nanowire,thus increasing the force between AgNWs and substrate.The resistance to 3M tape test was improved from 5 times to 200 times.Under the protection of nickel,the temperature endurance was increased greatly.Finally,a AgNWs/Ni-based TCF with sheet resistance of 9.8?/sq and transmittance of 95.3%can be achieved,which can withstand 400°C heat treatment.One-dimensional silver/carbon composite nanofibers?Ag/CNFs?were fabricated through electrospinning method followed by high-temperature treatment,and were used to prepare TCFs in the manner of partially substituting AgNWs.A maximum substitution value of 41.7%can be achieved.The deposition of AgNWs and Ag/CNFs in sequence was preferred.With the increase of the Ag/CNFs density,the sheet resistance of the TCFs decreased obviously at first and then increased slightly.When decreasing the fiber diameter,the transparency increased dramatically,while the conductivity changed slightly.A TCF with transmittance of 88% can be obtained using Ag/CNFs with a diameter of 30 nm.The TCFs with a sheet resistance of 83.0?/sq can be further improved to 50.0?/sq after experiencing proper heat treatment and acid immersion.Additionally,the as-prepared hybrid TCFs exhibited good flexibility,strong adhesion,and good resistance to high temperature as well as strong acid conditions.One-dimensional silver nanofibers?Ag-based NFs?were prepared by combining electrospinning method with medium-and low-temperature heat treatment,respectively.The mixture of polymer PVP and PEO can significantly reduce the decomposition temperature of silver nitrate,and thus forming a conductive film on PI substrate at 280°C.As the calcination temperature reached above 300°C,the polyimide substrate was decomposed under the catalytic oxidation of silver to form a conductive film with groove structure.By electroplating nickel,the grooves were almost filled up to obtain conductive films with excellent flexibility,scratch resistance and temperature endurance.In addition,a mixture of PVB and silver nanoparticles was used to fabricate AgNFs at a low temperature of 180°C.The PVB shrunk greatly to draw the silver nanoparticles closer,making the Ag-based NFs conductive.Self-supported AgNFs with secondary structure were fabricated successfully through electrospinning followed by the electroplating.The onset potential,half-wave potential,and peak potential of 1.041,0.848,and 0.864 V,respectively were achieved for the AgNWs with thorny structures,even superior to those of commercial Pt/C catalysts.Such excellent performance was attributed to two major factors,the micro morphology,i.e.thorn-on-fiber structure,and the crystal facet.The special thorny structure leads to the accumulation of electrons on the tip to act as highly active sites,while the high ratio of?110?facets on the tip favors high catalytic activity.In addition,this nanofiber-based catalyst demonstrated superior long-term stability and an unusually high methanol tolerant effect,with the ORR activities being enhanced,instead of lessened in 3 M methanol.This kind of cost-effective silver nanofiber-based catalyst exhibits a highly beneficial prospect as a potential alternative catalyst for ORR.