Insight Into the Effect of CuNi(111) and FeNi(111) Surface Structure and Second Metal Composition on Surface Carbon Elimination by O or OH: A Comparison Study with Ni(111) Surface

Abstract

A density functional theory (DFT) calculation has been carried out to systematically investigate the mechanism of surface carbon elimination by O and OH on both the alloy FeNi(111) and CuNi(111) surfaces, including the homogeneous and the segregated surfaces, respectively; meanwhile, the obtained results are compared with those on the pure Ni(111) surface in order to probe into the effects of CuNi(111) and FeNi(111) surface structure and second metal composition on the performance of surface carbon elimination. Our results show that compared to the pure Ni(111) surface, the introduction of Fe into Ni increases the adsorption of O, OH, and C species, while it weakens the adsorption of CO and COH; the incorporation of Cu into Ni decreases the adsorption ability of C, O, OH, CO, and COH species. The mechanism of surface carbon elimination by O and OH shows that OH species is more effective for carbon elimination than O species on Ni(111), CuNi(111) surface and the segregated FeNi(111) surface; meanwhile, CuNi(111) and FeNi(111) surface structure and second metal composition have obvious effect on the performance of carbon elimination. Compared to Ni(111), FeNi(111) surface is not favorable for carbon elimination, while CuNi(111) surface is beneficial for carbon elimination, in which the Cu enriched surface is much more favorable than the 1:1 Cu surface and the pure Ni(111), indicating that the segregated CuNi(111) surface with Cu enrichment significantly accelerates carbon elimination. Moreover, the good linear relationship exists between the average adsorption energy of C + O or C + OH and the activation barrier of the C + O(OH) reaction. As a result, once carbon is formed on the segregated CuNi alloy surface with Cu enrichment, carbon deposits can be timely eliminated, which can well explain the reported experimental facts that CuNi bimetallic catalysts with Cu surface enrichment display excellent carbonresistance ability in CH 4 /CO 2 reforming.

Mechanistic Insights for Dry Reforming of Methane on Cu/Ni Bimetallic Catalysts: DFT-Assisted Microkinetic Analysis for Coke Resistance

“…On the other hand, it also reveals the importance of OH species in bypassing the coke formation step from CH dissociation where kCH/kC(OH) >> kCH/kC(O), as shown in Figure 10. Comparing these results with previous studies [42,43], we can conclude that carbon elimination via C*+O* is enhanced in Ni2Cu (111) system over the Ni2Fe (111) and pure Ni (111) systems [19,25,28]. It suggests that the incorporation of Cu to Ni-Ni surface can simultaneously improve carbon elimination by C*+O* reaction, while reducing carbon deposition via CH dissociation.…”

Insight into the Reduction of NO by H2 on the Stepped Pd(211) Surface

“…It can be seen that transition states and activation energies are nearly same with different intermediate images. It can be concluded that four images is sufficient for the search of transition states, which was also used in other work. − …”

Comparative density functional theory study of carbon formation and removal mechanism on Rh modified Ni‐based catalyst in theCH4/CO2reforming

“…But the pure metal catalyst cannot meet the demand. Doping noble metals, such as Rh 11‐13 , Pt 14,15 , Pd 16 and else 17 , or non‐noble metals, such as Co 18,19 , Cu 20 , Fe 21,22 and Mg 23 , in another metal to form bimetallic catalyst has been studied extensively in experiments 24 and DFT calculations 25,26 . The energy barrier completely dissociated by CH 4 on the surface of M‐doped Cu(111)(M = Pt, Rh, Ni, Pd) was studied.…”