# Prospects and Technical Challenges in Hydrogen Production through Dry Reforming of Methane
## 2 Recent Advances on Catalysts for Syngas Production
### Transition Metals-Based Catalysts
#### 2.2.2 Cobalt Catalysts  
Along with nickel and its applications as DRM catalysts, cobalt has also been investigated as an alternative, inexpensive and earth-abundant metal with distinct catalytic activities for CH\({}_{4}\) reforming [73; 74]. However, cobalt-based catalysts have similar deactivation issues as those observed with nickel catalysts. Studies have shown that coke deposition is also a major trigger for Co-based catalysts deactivation, along with active sites oxidation [47; 75; 76]. Mechanistic studies via DFT showed that the metal-support interaction, metal distribution (related to the metal particle size) and active site oxidation stage play a significant role on the reaction rates for H\({}_{2}\) production and on the deactivation of cobalt sites during DRM. [77]. The influence of cobalt loading on sol-gel synthesized Co/MgO catalysts was investigated by [PERSON] et al. [47] with focus on the carbon deposition over the cobalt sites. The authors evaluated Co-loadings from 10 wt% to 25 wt% and reported an increase in the number of active sites at higher Co loads (20-25 wt%). On the other hand, the active phase at higher Co loads presented a weaker interaction with the catalyst support which led to a higher rate of carbon deposition. The similar catalytic activity shown by all evaluated catalysts showed a saturation behavior on the loading increase in Co. Furthermore, the authors evaluated the stability of 10 wt% Co/MgO catalyst for 50 h at 750 \({}^{\circ}\)C and reported the production of syngas with a H\({}_{2}\)/CO ratio of 0.94 along with high CH\({}_{4}\) and CO\({}_{2}\) conversions of 82% and 88%, respectively, and a low carbon formation rate (0.0072 g g\({}_{\text{cat}}\)\({}^{-1}\) h\({}^{-1}\)). [PERSON] et al. [78] investigated the promotion of ZrO\({}_{2}\)-supported Co catalysts with boron (B) for increasing reactivity towards CH\({}_{4}\) and CO\({}_{2}\) conversion. The authors showed that B impurities interacted with Co particles on the catalyst and increased hydrogen production as a result of increased reactivity of the Co/ZrO\({}_{2}\) catalyst by three times towards CH\({}_{4}\) decomposition. [PERSON] et al. [79] investigated the influence of CH\({}_{4}\):CO\({}_{2}\) feed ratio from 0.1 to 1.0 on the DRM activity of CeO\({}_{2}\)-supported Co catalysts synthesized with 20 wt% Co by incipient wetness impregnation. The authors also reported that the highest CH\({}_{4}\) (75-80%) and CO\({}_{2}\) (80-90%) conversions were obtained for a temperature of 750 \({}^{\circ}\)C. The final H\({}_{2}\)/CO ratio reached was 0.98-1.0 when the feed ratio (CH\({}_{4}\):CO\({}_{2}\)) varied between 0.8 and 0.9. Moreover, although no activity loss was observed during the tests, TEM images of spent catalysts showed that the particle size of active sites increased, which could, in turn, lead to sintering and irreversible deactivation. [PERSON] et al. [80] evaluated a novel filament-shaped mesoporous \(\gamma\)-Al\({}_{2}\)O\({}_{3}\) as catalyst support for 10 wt%Co nanoparticles and reported an increase in H\({}_{2}\) production when compared to commercial \(\gamma\)-Al\({}_{2}\)O\({}_{3}\) support. The authors reported that the highest CH\({}_{4}\) (76%) and CO\({}_{2}\) (82%) conversion was obtained at 800 \({}^{\circ}\)C and the H\({}_{2}\)/CO ratio increase from 0.83 to 0.89 when comparing the commercial as synthesized \(\gamma\)-Al\({}_{2}\)O\({}_{3}\) supports, respectively. On the other hand, the authors highlight that such H\({}_{2}\)/CO increase was a result of CH\({}_{4}\) cracking reaction (Equation (3)), which resulted in a higher carbon deposition (47 wt%) for the synthesized alumina support. Tungsten carbide (WC) has been referred to in literature as presenting activity comparable to noble metals and a \"Pt-like\" behavior for CO\({}_{2}\) conversion [81], which has motivated recent studies on its application [82; 83]. [PERSON] et al.