Mitigating Coke Formations for Dry Reforming of Methane on Dual-Site Catalysts: A Microkinetic Modeling Study

Dry reforming of methane (DRM) utilizes carbon dioxide (CO2) and methane (CH4) for syngas production. However, carbon accumulation leads to quick catalyst deactivation. In this study, we developed microkinetic models to describe dual-site catalyst systems to promote catalytic reactivity and suppress coke formation. These dual-site systems serve as idealized bifunctional catalyst models with well-defined active sites targeting different types of chemistries in one reaction network. According to density functional theory (DFT) calculations, the Co and Co-Mo2N interfacial sites in the Co-Mo ternary nitride (i.e., Co3Mo3N) show distinct reactivities toward CH4 decomposition and CHx oxidation, respectively. DFT calculations suggested that DRM intermediates (e.g., OH, CHO) do not always follow unified linear scaling relationships. Hence, a breakthrough was achieved from the limitations of the intrinsic linear correlations embedded in species adsorptions and activations. We employed microkinetic modeling to quantify the enhancement in syngas productions related to bifunctionality. Moreover, we confirmed that Co3Mo3N is the most effective in mitigating coke formation by facilitating the oxidation and transportation of carbonaceous species (e.g., C, CH) from the initial active sites to sustain a high reactivity. This work has shed light on rational catalyst designs to achieve high reactivity and long-term stability, especially for reactions such as DRM.