No 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.

No abstract

In this study, redox exsolution method was used to synthesize Co/Co−Al spinel for dry reforming. The aim is to improve metal‐support interaction, which enhances the catalyst's stability and minimizes carbon deposition. The synthesized catalysts were observed as Co embedded on Co deficient CoAl2O4‐like spinel (denoted as Co−Al spinel). The reduction temperature was optimized at 750 °C. Investigations on the effect of Co loading revealed that optimum Co loading is needed to control the Co particle size, providing balance between limiting carbon deposition rate and preventing dissolution of Co into the support. The best performing catalyst, Co‐15, in which the molar ratio of Co and Al is 15 : 85 produced a stable 81.5 % and 87.4 % conversions for CH4 and CO2 continuously over 24 h of reaction time with 13.51 wt% of carbon deposition. The strong metal‐support interaction of Co and Co−Al spinel in Co‐15 stabilizes and prevents the sintering of Co particles, enhancing the efficiency for dry reforming reaction.