CO Oxidation On Pt/WC(0001) And N Doped WC Clusters: A Density Functional Study

The estimated global reserves for Pt-group metals are extremely low,and they are remarkably expensive for widespread application commercially.To overcome this challenge,the alternative low-cost catalytic materials are strongly desired to reduce the Pt loading and promote the development of industry.Noticeably,tungsten carbide which has a similar electronic structure with Platinum has attracted widespread attention.Thus,WC is believed to have the potential to replace platinum as a catalyst and relieve the plight of decreasing platinum reserves.In this work,we evaluated a comparative study for H₂ O dissociation and CO oxidation on Pt/WC?0001?surface and Pt?111?surface using periodic,self-consistent density functional theory,and found that the activation barrier of H₂ O dissociation on the Pt/WC is similar to that of Pt.WC as a support plays an important role in enhancing catalytic activity by preventing agglomeration of Pt particles to possess high catalytically active surface areas and serves as an electronic promoter by modifying Pt d-band structure via charge flow from WC to Pt,which is beneficial for avoiding CO,CO2 and carboxyl intermediates adsorption on the surface and promoting the ability to oxidize the adsorbed CO-like species.Pt/WC surface can be easily covered by the OH species from the water which could facilitate the progress of CO oxidation by OH and subsequently removing as CO2.Mulliken population analysis showed that 0.280 e electrons were transferred to every Pt atom from WC which leading the d-band center shift to a lower energy.The accumulating charge on Pt atoms will reduce the bonding effect between the CO 5? and the metal d orbital.Moreover,the back-donation of charge from Pt d orbital to the CO 2?* orbital is weakened for the downshift of the d-band center.This well explained that the Pt/WC surface is more CO-tolerant than the pure PtIn order to understand the WC nanoparticles more in detail,we considered a sufficient number of initial configurations for each?WC?_n cluster and find their lowest energy configurations,which is used for further N-substitution doping.A cubic-like growth of WC clusters was found to be the preferred pathway.The average binding energy increases monotonically with the cluster size.Changing the doping site of N atoms has little effect on their cluster stabilities,but not for the highest occupied molecular orbital-lowest unoccupied molecular orbital gaps.According to the PDOS and Milliken analysis of W6C5 N isomers,we find that the Cedge substitution doping of W6C5N-2 shows a higher chemical activity for the total electron?1.829e?lost by the W atoms are less than the host structure of 1.920 e,resulting in increased anti-orbital filling and the active electrons near the Fermi level.Thus,it is possible to modify the properties of tungsten carbonitrides through directed regulation of the atomic ordering of nonmetal atoms without appreciably change the cluster stability.