The density functional theory studies on the promoting effect of the Cu-modified Fe3O4 catalysts

• The presence of Cux on the Fe3O4 can activate the Fe3O4 surface for CO adsorption.
• The Cux/Fe3O4 can reduce the adsorption energy difference between H2O and CO.
• The Cu-modified Fe3O4 provides CO with more stable adsorption sites.
• The coadsorption of CO and H2O can steadily coexist on the Cux/Fe3O4 surface.
• The present work sheds light on the beneficial effect of Cu on the Fe3O4 surface.

The adsorption of carbon monoxide and water on the Cux/Fe3O4(111) surface (the Fe3O4(111) surface modified by the small Cux (x=1–4x=1–4) clusters) is investigated. It is found that the addition of Cu to the Fe3O4(111) plays a critical role in activating the surface for CO adsorption. The presence of Cux clusters on the surface enhances the adsorption of CO, which would provide the CO with more stable adsorption sites and harmonize the coadsorption of CO and H2O on the Cux/Fe3O4 surface. The results shed light on the promoting effect of the Cu-modified Fe3O4 catalysts.