DFT Study on the Synergistic Effect of Pd–Cu Bimetal on the Adsorption and Dissociation of H₂O

Abstract

Aiming at exploring the effect of surface composition on the catalytic activity by density functional theory, the adsorption and complete dehydrogenation mechanisms of H 2 O 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 H 2 O 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 H 2 O 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 H 2 O 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 H 2 O 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.

Water Adsorption and Dissociation on Copper/Nickel Bimetallic Surface Alloys: Effect of Surface Temperature on Reactivity

“…34 Among the five surface alloys with varying concentration of Pd (Pd x −Cu 4-x ; x = 0−4), Pd 2 −Cu 2 (100) surface with two surface Pd atoms was found to be kinetically and thermodynamically optimal for H 2 O dissociation. 38 Similarly, Fe(111) surface with a barrier of 1.05 eV for H 2 O dissociation showed a decrease in the activation barrier heights to 0.55 and 0.43 eV, respectively, for surface alloys obtained by replacement of 1 and 2 surface atoms by W thereby highlighting the advantages of using surface alloys in catalysis. 39 The aim of this work is to understand the rate-determining water adsorption and dissociation step of WGS reaction on bimetallic close-packed surface alloys of Cu and Ni and pin down the reactivity change to one or more electronic effects.…”

“…Very recently, H 2 O adsorption and dissociation was studied on Pd–Cu(100) bimetallic surface alloy wherein Pd metal belongs to the same group as nickel. Among the five surface alloys with varying concentration of Pd (Pd x –Cu 4‑x ; x = 0–4), Pd 2 –Cu 2 (100) surface with two surface Pd atoms was found to be kinetically and thermodynamically optimal for H 2 O dissociation . Similarly, Fe(111) surface with a barrier of 1.05 eV for H 2 O dissociation showed a decrease in the activation barrier heights to 0.55 and 0.43 eV, respectively, for surface alloys obtained by replacement of 1 and 2 surface atoms by W thereby highlighting the advantages of using surface alloys in catalysis …”

Theoretical Study of Hydrogen on LaFeO3 (010) Surface Adsorption and Subsurface Diffusion

“…Then the most stable adsorption position of the surface is taken as the initial structure, the best-occupied position of the subsurface is taken as the final structure, and the transition states [25,26,27] are searched by combining linear synchronous transit (LST) with quadratic synchronous transit (QST) methods [28]. We used the functions of TS-Confirmation [29] to confirm the transition state. For detailed instructions, see supplementary material.…”

Efficient Water–Gas Shift Catalysts for H2O and CO Dissociation Using Cu–Ni Step Alloy Surfaces

“…Bimetallic alloy catalysts have been shown to improve the reactivity and the selectivity for dissociation of H 2 O due to the synergy effect, − interatomic arrangements, greater flexibility in chemical compositions, etc. − ,− Doping of metal catalyst surfaces with other metals leads to a cooperative effect that stabilizes water adsorption, H + OH co-adsorption, and the transition-state (TS) configuration .…”