Investigation Of Copper-Cerium Based Catalysts For Preferential Oxidation Of Carbon Monoxide

Energy shortage and environmental problems caused by the rapid development of social economy have been received widely concerns,leading to exploration of sustainable energies.Among investigated the hydrogen energy is regarded as a promising candidate.The proton exchange membrane fuel cells（PEMFC）are effective ways to convert hydrogen energy whereas the residual CO in H₂-rich stream could poison the Pt anode of PEMFC.Among investigated ways to remove CO,preferential oxidation of CO（CO-PROX）is the most economic and effective method.Owing to the excellent high temperature reactivity and high CO₂ selectivity,Cu-Ce binary oxides are widely investigated for CO-PROX reaction.However,the Cu-Ce catalysts exhibited poor activities at low temperatures and could be easily poisoned by CO₂ and H₂O contained in industrial hydrogen-rich atmosphere,resulting in the decrease in stability.Herein,noble metal and nonmetal species were introduced to adjust the composition,structure and chemical states of the Cu-Ce catalysts,aiming to enhance the performance of catalysts.Based on characterization methods such as in-situ DRIFTS etc.,the influence of physical and chemical properties on reaction performance was explored and the structure-activity relationship was established.1.A series of Ir/Cu_xCe_1-x（x=0,0.05,0.09,0.17,1）catalysts were obtained by the Cu_xCe_1-x（x=0,0.05,0.09,0.17,1）supports synthesized via a sol-gel method,followed by deposition of Ir by deposition precipitation method.The morphology,composition and structure of the synthesized catalysts were characterized.Then the catalysts were evaluated for preferential oxidation of CO（CO-PROX）reaction.It was found that the Ir/Cu_0.09Ce_0.91 exhibits a wide operating temperature window form 80℃-180℃after introduction of Ir,which is wider than Cu_0.09Ce_0.91.2.The stability test shows that Ir/Cu_0.09Ce_0.91 catalyst exhibits excellent resistance to H₂O and CO₂ poison.The combination of XPS,Raman,in-situ DRIFTS and micro-reaction kinetics tests reveal that the excellent performance of Ir/Cu_0.09Ce_0.91 catalyst can be due to the strong interaction between Ir and Cu species.Through this interaction,the CO was mainly adsorbed on Cu sites and the Ir sites become the adsorption and activation of H₂/H₂O.The adsorbed CO could easily react with hydroxyl species formed via activation of H₂/H₂O to generate easily decomposed bicarbonate species,which contributes to the resistance of the catalysts to H₂O and CO₂ poison.3.The introduction of non-noble metal Si into the Cu-Ce catalysts could promote the conversion of CO.The 100%of CO conversion and high CO₂ selectivity from 100-220°C was achieved for Cu1.0Si/Ce O₂.The characterization results demonstrate that the Si species could promote the reduction of Cu O_x and then stabilize the oxidation of Cu at Cu⁺,favoring the CO adsorption.Furthermore,the H₂ was facilely adsorbed on Si species could favor the formation of easily decomposable bicarbonate species.As a result,the high activity and CO₂ selectivity were presented for Cu1.0Si/Ce O₂ catalyst.