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-Cu0-4, Pd-Cu1-3, Pd-Cu2-2, Pd-Cu3-1,, and Pd-Cu4-0 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 P-d-Cu4-0 and Pd-Cu3-1 surfaces and can promote the scission of H-O bond of OH except for that on the Pd-Cu4-0 surface. Compared with that on other Pd-Cu (100) surfaces, it can be proposed that the Pd-Cu2-2 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.