DFT study on the synergistic effect of Pd-Cu bimetal on the adsorption and dissociation of H₂O

Aiming at exploring the effect of surface composition on the catalytic activity by density functional theory, the adsorption and complete dehydrogenation mechanisms of H₂O on five Pd-Cu (100) surfaces have been investigated. With regard to adsorption, it is found that the adsorption OH, O, and H on Pd-Cu_0-4, Pd-Cu_1-3, Pd-Cu_2-2, Pd-Cu_3-1, and Pd-Cu_4-0 surfaces are chemisorption and that of H₂O may be considered as physisorption. Interestingly, it is revealed that the difference of Pd-Cu doping ratios has no effect on the adsorption configurations of all intermediates; nevertheless, it has an evident influence on the interaction between adsorbates and substrates. In addition, the energy pathways for the complete dehydrogenation of H₂O on five Pd-Cu (100) surfaces are analyzed to explore the dissociation mechanisms. It is found that the doped Pd atoms on the first layer of Cu (100) surface are beneficial for the scission of H-O bond of H₂O except for that on the Pd-Cu_4-0 and Pd-Cu_3-1 surfaces and can promote the scission of H-O bond of OH except for that on the Pd-Cu_4-0 surface. Compared with that on other Pd-Cu (100) surfaces, it can be proposed that the Pd-Cu_2-2 surface is the optimal surface for H₂O dissociation in kinetic and thermodynamic aspects. Therefore, by way of regulating the doped ratios of metal surfaces, the activity and selectivity of catalysts may be modulated effectively.