Study On The Cu/Fe₃O₄ WGS Catalysts Prepared With The Co-precipitation Method:Relationship Between Structure And Performance

It is extremely urgent that we need to develop new sources of energy to solve the serious shortage problem of energy. Compared with traditional fossil fuels, hydrogen energy has attracted the scientists’ attention due to its high energy, non-toxic, renewable, etc. Nowadays, the production of hydrogen is mainly based on the catalytic steam reforming of natural gas, coal gasification and so on. However, The reformed fuel contains a bit of CO, which may degrade the performance of the Pt electrode. With the development of fuel cell, water-gas shift catalysts have aroused the interest of scientists because of its removal of CO and production of H2 simutaneously in the water-gas shift reaction (WGSR). Whereas,Traditional WGS catalysts can not meet the needs of the fuel cell because of their disadvantage such as poor thermal stability, tedious vulcanization process, etc. It is essential to develop new WGS catalysts. Therefore, the Cu/Fe3O4 WGS catalysts were employed as research objects due to their low costs as well as good catalytic performance in this work.In this present work, we obtained a series of Cu/Fe3O4 WGS catalysts. The catalytic performance, which affected by structure of the catalyst, physico-chemical properties and surface properties, was investigated by N2-physisorption, XRD, H2-TPR, CO2-TPD, O2-TPO, Raman, SEM and N2O decomposition.Firstly, we investigated the effect of different precipitants (KOH, K2CO3, Na2CO3, NaOH, and NaHC03) on the structure and activity of Cu/Fe3O4 catalysts. The result shows that the catalyst prepared by the KOH exhibit much better activity. It is suggested that higher Cu dispersion, larger BET surface area, larger amount of weak basic sites, and strong synergistic interaction between copper and iron oxides are responsible for the high catalytic performance.Secondly, the dopant (ZnO) was added to modify the Cu/Fe3O4 WGS catalysts. We synthesized a series of Cu/Fe3O4-ZnO catalysts by stepwise precipitation with KOH as precipitant. The result shows that the modified catalyst (2.5 wt.% ZnO) can improve reducibility due to its higher Cu dispersion. Moreover, it can promote dissociation of H2O and adsorption of CO because of its larger amount of weak or medium basic sites. Hence, Cu/Fe-Zn2.5 performs better activity and thermal stability.In addition, the dopant (Le2O3) was added to modify the Cu/Fe3O4 WGS catalysts. However, the addition of La2O3 reduces the interaction between copper and iron oxide, refrains the production of main phase of CuFe2O4, results in the declining of amount of active copper species. It weakens the reductive performance and catalytic activity of catalysts.