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Mechanism of methanol decomposition on the Pd/WC(0001) surface unveiled by first-principles calculations
Frontiers of Chemical Science and Engineering ( IF 4.5 ) Pub Date : 2020-03-27 , DOI: 10.1007/s11705-019-1908-y
Jinhua Zhang , Yuanbin She

In this study, the decomposition of methanol into the CO and H species on the Pd/tungsten carbide (WC)(0001) surface is systematically investigated using periodic density functional theory (DFT) calculations. The possible reaction pathways and intermediates are determined. The results reveal that saturated molecules, i.e., methanol and formaldehyde, adsorb weakly on the Pd/WC(0001) surface. Both CO and H prefer three-fold sites, with adsorption energies of – 1.51 and – 2.67 eV, respectively. On the other hand, CH3O stably binds at three-fold and bridge sites, with an adsorption energy of – 2.58 eV. However, most of the other intermediates tend to adsorb to the surface with the carbon and oxygen atoms in their sp3 and hydroxyl-like configurations, respectively. Hence, the C atom of CH2OH preferentially attaches to the top sites, CHOH and CH2O adsorb at the bridge sites, while COH and CHO occupy the three-fold sites. The DFT calculations indicate that the rupture of the initial C-H bond promotes the decomposition of CH3OH and CH2OH, whereas in the case of CHOH, O-H bond scission is favored over the C-H bond rupture. Thus, the most probable methanol decomposition pathway on the Pd/WC (0001) surface is CH3OH → CH2OH → trans-CHOH → CHO → CO. The present study demonstrates that the synergistic effect of WC (as carrier) and Pd (as catalyst) alters the CH3OH decomposition pathway and reduces the noble metal utilization.



中文翻译:

第一性原理揭示了甲醇在Pd / WC(0001)表面上的分解机理

在这项研究中,使用周期性密度泛函理论(DFT)计算系统地研究了甲醇在Pd /碳化钨(WC)(0001)表面上分解为CO和H物种。确定了可能的反应途径和中间体。结果表明,饱和分子,即甲醇和甲醛,在Pd / WC(0001)表面上的吸附较弱。CO和H都更喜欢三重位点,其吸附能分别为– 1.51和– 2.67 eV。另一方面,CH 3 O稳定地在三重桥位结合,吸附能量为– 2.58 eV。但是,大多数其他中间体往往会分别以sp 3和类似羟基的构型吸附碳和氧原子。因此,CH的C原子2 OH优先附着在顶部位点,CHOH和CH 2 O吸附在桥位,而COH和CHO占据三重位。DFT计算表明,初始CH键的断裂促进了CH 3 OH和CH 2 OH的分解,而在CHOH的情况下,OH键断裂比CH键断裂更有利。因此,Pd / WC(0001)表面上最可能的甲醇分解途径是CH 3 OH→CH 2 OH→反式-CHOH→CHO→CO。本研究证明了WC(作为载体)和Pd的协同作用。 (作为催化剂)会改变CH 3 OH的分解途径并降低贵金属利用率。

更新日期:2020-04-21
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