Silica-Confined Two-Atom Single-Cluster Catalyst for Direct Nonoxidative Conversion of Methane: A DFT Study
journal contribution
posted on 2021-10-13, 18:46 authored by Han-Xuan Liu, Tao Ban, Xi-Yang Yu, Zheng-Qing Huang, Chun-Ran ChangThe
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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preferentially generated vialower top pointfree energy profiledensity functional theoryunique dissociation channelc © sio32 ev ).lower activation barrierfe © siocluster catalyst denotedatom iron catalystdirect nonoxidative conversion2 subnonoxidative conversionactivation barriercluster catalystc *)atom single94 ev42 evmethane dissociationtarget productstill requiredresults demonstrateresistant behaviorresistance abilitypoisonous methinephase mechanismnaked carbonhigh temperatureharsh conditionsdetermining stepconfined single
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