Silica-Confined Two-Atom Single-Cluster Catalyst for Direct Nonoxidative Conversion of Methane: A DFT Study
journal contributionposted on 2021-10-13, 18:46 authored by Han-Xuan Liu, Tao Ban, Xi-Yang Yu, Zheng-Qing Huang, Chun-Ran Chang
The direct, nonoxidative conversion of methane achieved a breakthrough with the development of a silica-confined single-atom iron catalyst (Fe©SiO2). However, improving the catalyst from high temperature and harsh conditions is still required. Here we designed a two-atom single-cluster catalyst denoted as Fe2C©SiO2 and revealed its performance on the nonoxidative conversion of methane by density functional theory (DFT) calculations. The results demonstrate that the dual Fe–Fe sites provide a unique dissociation channel for methane, which reduces the activation barrier of methane dissociation by 0.42 eV. On the designed Fe2C©SiO2 catalyst, the target product (ethylene) is preferentially generated via the surface coupling mechanism rather than the gas-phase mechanism, indicated by the lower top point of the free energy profile (2.85 eV vs 3.94 eV) and the lower activation barrier of the rate-determining step (2.12 eV vs 2.32 eV). The coke-resistance ability of Fe2C©SiO2 was evaluated by the deep dehydrogenation of methyl (CH3*), which shows that the dehydrogenation of methyl to methylene (CH2*) is readily to occur, but its deep dehydrogenation to poisonous methine (CH*) or naked carbon (C*) is significantly more difficult than the competing CH2* coupling reactions, demonstrating the remarkable coke-resistant behavior of the catalyst.
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