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有关用于各种氧化反应中Au-Ag双金属催化剂存在显著协同效应的来源有两种观点:(1)AgO_x块与体相Au表面的接触界面起重要作用,体相Au的表面是催化活性位;(2)Au-Ag双金属催化剂中形成的Au-Ag合金中电荷从Ag转移到Au上,可能对催化剂活性起作用.因此,确定Au表面上Ag是以氧化物还是以金属合金形式存在可能是深度理解该协同效应的关键.为了检测和验证催化剂活性的增加是由于Ag_2O与Au纳米粒子的紧密接触,在密闭循环反应体系中比较研究了Au/Ag_2O和Ag_2O催化剂上CO氧化反应.将CO/O_2摩尔比为2的混合气通入到这二个催化剂上来跟踪压力降低的速率.因而检测了气体的消耗量和CO_2的生成量.结果发现,在稳态下Au/Ag_2O和Ag_2O催化剂的压力降低的速率不存在差别.这两个催化剂上压力的降低是由于Ag_2O中表面晶格氧被混合气中CO的还原所致.Au/Ag_2O催化剂上得到的结果与以前研究的具有氧化表面的Ag掺杂的Au粉末(Ag/Au-b)上的一致,也表明AgO_x块与体相Au表面界面周边不大可能是CO氧化反应催化活性位.基于具有稳态表面的Ag/Au-b样品上的研究结果,我们认为AgO_x物种被还原为0价态Ag而形成的Ag-Au合金很可能是催化活性位.
There are two sources for the existence of a significant synergistic effect for the Au-Ag bimetallic catalysts used in various oxidation reactions: (1) the contact interface between the AgO_x bulk and the bulk Au surface plays an important role, and the surface of the bulk Au is catalytically active (2) Au-Ag alloy formed in the Au-Ag bimetallic catalyst, the charge transfer from Ag to Au may play a role in the activity of the catalyst.Therefore, it is determined whether Ag on the Au surface is oxidized or in the form of a metal alloy Which may be the key to understanding the synergistic effect in depth.In order to detect and verify the increase of catalyst activity, the oxidation of CO on Au / Ag_2O and Ag_2O catalysts was investigated in a closed-cycle reaction system due to the close contact between Ag_2O and Au nanoparticles. The gas mixture with CO / O 2 molar ratio of 2 was introduced into these two catalysts to track the rate of pressure decrease, and the gas consumption and CO 2 production were measured. It was found that Au / Ag 2 O and Ag 2 O There was no difference in the rate at which the pressure of the catalyst was reduced.The reduction in pressure on these two catalysts was due to the reduction of the surface lattice oxygen in the Ag 2 O by the CO in the gas mixture.The results obtained on the Au / (Ag / Au-b) with an oxidized surface also showed that the periphery of the AgO_x bulk-to-bulk Au surface interface was not likely to be the CO oxidation catalytically active site. Ag / Au-b samples on the results of the study, we believe that AgO_x species is reduced to 0 valence state Ag and the formation of Ag-Au alloy is likely to be catalytically active.