The Synthesis Of Cu-based Nano-structures And Their Catalytic Properties

In this thesis,we reported three types of Cu-based nano-structures(including Cu nanowires,Cu nanoparticles and polyhedral Cu2O microcrystals),which were synthesized by liquid-phase reduction method and demonstrated preferable catalytic performances.Firstly,we provided an effective route to achieve the "sustainable oxidation resistance" for Cu NPs,resolving the oxidation bottleneck of Cu nanomaterials.Once an oxide layer is formed by the external environment,an ageing treatment would remove the oxide layer.This ageing treatment takes advantage of the two functions for the citrate groups:one is their complexation with the Cu2+,which facilitates the Cu2O etching;the other is their interaction with the Cu,which enhances the oxidation resistance for the Cu surface.By the ageing treatment,the oxide layer was removed and the formed fresh Cu was protected by the citrate group,which enhanced the oxidation resistance.Since there is no long or hydrophobic-ligand,the adsorption and desorption of the reactant could proceed smoothly on the Cu surface.In the 4-nitro-phenol(4-NP)reduction,rate constant of the reaction catalyzed by the Cu NPs is estimated to be 0.0385/s,which is much superior to that by Ag and Au NPs.Compared with noble metals,preparation of Cu nanomaterials with well-defined shapes is still challenging.The conventional amine-assisted synthesis is not only hindered by restricted by the high reaction temperature but the eliminating of surface amine molecules.Secondly,we successfully synthesize the surface-cleaned Cu NWs under a mild condition.Results of analyses demonstrated that the "clean surface" provides more available active sites for the efficient transfer of electrons,resulting in the Cu NWs exhibit show their enhanced electro-catalytic activity.In the MOR,the surface-cleaned Cu NWs exhibited 6.45 times higher forward peak current density than the Cu NWs with residual capping molecules.The "clean surface" effect can also be applied to the glucose electro-oxidation reaction,and the enhancement in electro-catalytic activity is 11.3 fold.Moreover,the Cu NWs exhibit a lower over-potential to achieve the methanol electro-oxidation reaction(MOR)than that of analogous Cu nanoparticles(NPs).The lower over-potential can be rationalized by the path directing effects and abundant(100)facets.Since the onset potential is one important parameter to evaluate the catalyst efficiency,this finding opens up new avenues for utilizing non-noble metals in the fuel cell or biofuel cell applications.Finally,we applied the "clean surface" effect to Cu2O which is another kind of Cu-based nano-materials.Four different shapes of polyhedral Cu2O microcrystals(concave cubic,multiple-branching,extended hexapod and short hexapod)have been synthesized,by using KBr as the addtive.The four kinds of Cu2O microcrystals obtained were further utilized in the non-enzymatic amperometric glucose sensors.Among the four kinds of polyhedral Cu2O,the extended hexapod Cu2O show the widest detection,which is up to 14.3 mM.This detection ranges are much closer to the human physiological level.The extended hexapod Cu2O can also be applied in H2O2 sensor.This work enhanced the catalytic performance or oxidation resistance of Cu-based nano-structures without the need for additional composite.All the synthesis route provided in this thesis were non-toxic,scalable and cost effective.Since the Cu is more abundant and less expensive,this thesis provides new avenues for obtaining the alternative to the noble metal micro/nanomaterials.