Molecular orientation effect on CO adsorption on Pd(111) surface

CO is known as one of the main gas for Pd alloy membrane poisoning during hydrogen permeation.A scheme is put forward to reduce CO adsorption on Pd alloy membrane by modifying the CO molecular orientation. On this basis, two structures of different molecular orientation on Pd(111) surface at 0.75 coverage of monolayer have been calculated using density functional theory.It is found that the structure with carbon near Pd(111) surface is stable while the structure with oxygen is quite difficult, therefore, controlling the orientation of CO molecule adsorbed on Pd surface may be effective to inhibit CO adsorption on Pd surface.