First-principles And Experimental Studies On Cu@CuO/Ag Core-shell Nanomaterials

With the gradual progress of modern science,catalysts with nano-scale core-shell structures have begun to come into view.Nanoscale core-shell catalysts are mainly composed of a kind of nanoparticles through chemical interaction to wrap up another kind of nanoparticles to form an ordered assembly structure,which can effectively prevent the migration of active sites and improve the catalytic performance.As a common catalyst,CuO is widely used in the field of photocatalysis because of it has1.2 e V?1.5 e V band gap and unique photochemical properties.But,CuO has the high recombination rate of photogenerated e/h⁺,the researchers usually use other materials to reduce the probability of e/h⁺recombination.In this paper,with the purpose of using CuO to inhibit the agglomeration of nano-Cu cores and creating synergy between the Cu core and the CuO shell layer,nano-Cu is selected as the catalyst carrier,and CuO is the shell in Cu@CuO core-shell material.For explore the influence of Ag element doping on aspects of the structure.The paper has two part,First principles study and experiment:using Materials Studio 8.0 simulation software to build Cu@CuO core-shell structure model,comparing with the effect of Ag atom doping on the electronic structure and catalytic performance of Cu@CuO.Adopting the method of chemical plating samples of Cu@CuO and Cu@CuO/Ag were prepared,and the simulation results were verified by experiments.The results are as follows:The structural model of seven kinds of Ag atoms doped on Cu@CuO was established,and the calculation results showed that the doping behavior of Ag atoms in the O-O hole was most likely to occur.Charge transfer analysis showed that the doping of Ag atoms would reduce the electric potential of the Cu@CuO,thereby making the surface properties of Cu@CuO/Ag more active.The band analysis results showed that the band gap value of Cu@CuO/Ag is 0.133 e V,Cu@CuO is 0.263 e V,and the stability of Cu@CuO/Ag is lower,so the catalytic reaction is easier to be performed.The calculation results of HOMO-LUMO indicated that the doping of Ag atoms makes some Cu atoms congest the Cu@CuO surface.The number of lone electron pairs increased,and the lone electron pair of the internal Cu core disappears.By simulating the decomposition path of H₂O₂,it is clear that the decomposition path of H₂O₂on the Cu@CuO,Cu@CuO/Ag core-shell structure is that the O-O bond breaks first.That is:H₂O₂?2OH?H₂O+O,and doping of Ag atoms accelerates the decomposition rate of H₂O₂.Two samples of Cu@CuO and Cu@CuO/Ag were prepared.The XRD test results showed that doping of Ag caused lattice distortion inside the crystal and the absorption peak shifted to the left;the results of TEM reveal that:Ag element is attached to the CuO shell in the form of rectangular nano bars,and Ag element will cause the interface boundary between Cu and CuO to be blurred.The photocatalytic performance test results showed that the degradation rate of methyl orange by Cu@CuO/Ag was significantly increased when the xenon lamp was irradiated for 20min?30 min,and the absorbance of degraded methyl orange by Cu@CuO/Ag after 40min reduced to about 1.5 a.u,the absorbance of degrading methyl orange by Cu@CuO is maintained about 2.7 a.u,indicating that Ag doping increased the rate of degradation of methyl orange by Cu@CuO.