In-situ Study Of Water-gas Shift Reaction At Metal-oxide Interfaces Using Surface-enhanced Raman Spectroscopy

As one of the important reactions for the production of high-purity hydrogen,the water-gas shift reaction has become a research hotspot.And the noble metal Pt-based catalysts show excellent water-gas shift reaction activity under low temperature conditions,but due to the lack of direct evidence,the mechanism of the water-gas shift reaction is not clear.The discovery of surface-enhanced Raman spectroscopy(SERS)has greatly improved the sensitivity of traditional Raman spectroscopy,making Raman a highly sensitive surface interface analysis technique that can be applied to in-situ monitoring of catalytic reaction processes.Based on this,this thesis constructed Au@Pt@oxide nanoparticles with a ternary core-shell structure and obtained Pt-oxide interface on the surface of Au nanoparticles with high SERS enhancement ability.And in-situ SERS was utilized to monitor the water-gas shift reaction process at the Pt-oxide interface.The specific contents are as follows:1.Firstly,Au@Pt@NiO nanoparticles with a ternary core-shell structure were prepared by the seed growth method.By controlling the amount of nickel precursor,a series of Au@Pt@NiO nanoparticles with different NiO coverage were obtained,and the Pt-NiO interface was successfully constructed on the surface of Au nanoparticles.In-situ SERS was used to monitor the water-gas shift reaction process on the Pt-NiO interface.Direct spectroscopic evidence of the carbonate intermediate species and its dynamic transformation during the water-gas shift reaction were obtained.It shows that the water-gas shift reaction on the Pt-NiO interface followed the association mechanism related to carbonate.A possible path for the generation of carbonate is proposed:CO is first adsorbed on the surface of Pt and reacts with the-OH dissociated by H2O on NiO to generate carbonate.In addition,by combining the activity results of the Pt/NiO catalyst in simulating the actual water-gas shift reaction,it is speculated that the decomposition of carbonate may be the rate-determining step of the reaction.2.Using ALD technology,different thicknesses of TiO2 were deposited on the surface of Au@Pt nanoparticles to constructe Au@Pt@TiO2 nanoparticles with a ternary coreshell structure.And the mechanism of the water-gas shift reaction on the surface was initially explored by in-situ SERS.The results show that the Raman spectroscopy evidence of the H2O-related intermediate species during the water-gas shift reaction and their dynamic transformation process can be obtained only at the Pt-TiO2 interface,which verifies that the water-gas shift reaction occurs at the Pt-TiO2 interface.It is speculated that the water-gas shift reaction at the Pt-TiO2 interface may follow the redox mechanism.