Dry Reforming of Methane on Cobalt Catalysts: DFT-Based Insights into Carbon Deposition Versus Removal

Abstract

Identifying the origin of carbon deposition in reactions, such as dry reforming of methane (DRM) over cobalt (Co) nanocatalysts, is an important yet challenging issue in heterogeneous catalysis. In this study, we used density functional theory (DFT) calculations to investigate the surface reactions of CO2 with C* at the flat and step sites of face-centered cubic (FCC) Co [(111), (110), (100), (211), and (221)], which represent the major surfaces of Co nanoparticles. The results were being compared with Ni nanoparticles. Hereby, we identified that the high degree of preference for C–C coupling over CO* formation, especially on Co(111), serves as the origin of carbon graphitization. This finding is similar to that on Ni(111). Furthermore, we reported for the first time that the significant difference between Co and Ni is due to CO2 activation, which is far more favored on Co than on Ni, accounting for the lower carbon deposition on Co. On the other hand, within the investigated surfaces of Co, step and less common surfaces, namely, Co(211), Co(221), and Co(100), do not favor C–C coupling. Based on our findings, we proposed that high-index-facet, surface-modified, and/or promoted Co nanoparticles be used for DRM to restrict C–C coupling.