CH4 dissociation and C C coupling on Mo-terminated MoC surfaces: A DFT study

Abstract Synthesizing high-value chemicals through C C coupling of the intermediates from CH4 dissociation is considered as the most promising pathway for efficient utilization of methane as a C1 resource. Herein, the elementary steps of CH4 dissociation and a possible mechanism for forming C2 species on the Mo-terminated MoC surfaces were studied using density functional theory (DFT) calculations. Our results indicate that the Mo-terminated MoC surfaces derived from different bulk phases (α- and δ-) of MoC possess a similar mechanism to that on the noble-metal surfaces for methane dissociation, i.e., CH4 dissociates sequentially to (CH)ad with both kinetic and thermodynamic feasibililies while breaking the last C H bond in (CH)ad is highly activated. As such, C C coupling through dimerization of the (CH)ad species occurs more readily, resulting in (C2H2)ad on the Mo-terminated surfaces. Such (C2H2)ad species can dehydrogenate easily to other C2 adsorbates such as (C2H)ad and (C2)ad. Consequently, these C2 species from CH4 dissociation will likely be the precursor for producing long chain hydrocarbons or aromatics on molybdenum carbide based catalysts.