Synergistic Mechanism Of Pt-enhanced Copper-based Catalysts And Their Performance Research During Preferential Oxidation Of Carbon Monoxide

Hydrogen is regarded as a clean energy source.Proton exchange membrane fuel cells?PEMFCs?,as efficient energy conversion devices,are widely used for the conversion of hydrogen energy.The residual CO?about 1%?in the hydrogen-rich gas after water-gas shift will poison the Pt electrode of PEMFCs.Therefore,effective means should be used to reduce the CO concentration in the hydrogen-rich gas to below 100 ppm.Currently,CO preferential oxidation?CO-PROX?is an effective method to remove CO from a hydrogen-rich gas.Copper-cerium catalysts are considered to have good application prospects due to low cost and high activity,but their catalytic activity at low temperature still needs to be improved.Since the Pt-based catalysts exhibit good low-temperature catalytic activity for CO oxidation,the copper-cerium catalysts modified by Pt are expected to improve the catalytic performance of CO-PROX at low temperature.In this thesis,the Pt-modified copper-based catalysts applied for CO-PROX were studied to clarify the mechanism of the synergistic effect between Pt and Cu enhancing the catalytic performance.The catalytic mechanism,structure-activity relationship and regulation methods were revealed at the atomic scale.The specific research contents are as follows:A series of Pt/CuO-CeO₂ catalysts were prepared by template method combined with liquid phase reduction method to investigate systematically the effect of Pt loading on the catalytic performance of CO-PROX.The results show that the higher Pt content can effectively promote the reduction of copper and cerium,and increase the CO adsorption site,thus improving the catalytic activity of CO-PROX at low temperature.According to CO-TPD results,the narrower CO complete conversion temperature window results from the fact that more CuO species were reduced to Cu⁰by excessive NaBH₄ reductant,which reduces the number of active sites at the interface.A series of Pt-Cu/CeO₂ catalysts with low Pt content were prepared by deposition precipitation method to investigate systematically the effect of Cu content on the catalytic performance of CO-PROX.It is found that controlling the Pt/Cu ratio can effectively improve the electronic structure of the catalyst,thereby promoting the adsorption and oxidation of CO.The results show that the Pt10Cu19/CeO₂ catalyst exhibits higher catalytic activity at low temperature.In addition,the synergy between Pt and Cu can inhibit the adsorption and oxidation of H₂,which is helpful to improve the CO₂ selectivity of the catalysts.The PtCu hollow alloy nanocage catalyst with different crystal facets exposed was constructed by the sacrificial template method and the modified electrochemical replacement method.The results show that the coexisting crystal facets of?111?and?100?contribute to increase the electron density of Pt,generate more CO and O₂adsorption activation sites,and reduce the adsorption strength of CO on the Pt surface,thus showing a higher CO-PROX catalytic activity and CO₂ selectivity.