Complexity of a Co₃O₄ System under Ambient-Pressure CO₂ Methanation: Influence of Bulk and Surface Properties on the Catalytic Performance

Abstract

Although using supported noble-metal catalysts for CO2 hydrogenation is an effective solution due to their excellent catalytic properties, metal oxide supports themselves can exhibit good activity being more economically feasible. This work focuses on investigating the complexity of the Co3O4 system during the CO2 methanation reaction, which is usually accompanied by the formation of unstable dispersions of cobalt oxide and metallic Co. Herein, we have tested different types of Co3O4: synthetically prepared mesoporous m-Co3O4 (BET surface area, 95 m2/g) and commercial c-Co3O4 (BET surface area, 15 m2/g; purchased from Merck) in the CO2 methanation reaction under different reduction temperatures (273–673 K). The reduction temperature was adjusted to 573 K for both the catalysts to reach the optimal Co/cobalt oxide ratio and consequently the best catalytic performance. m-Co3O4 is more active (CO2 conversion 95%) and stable at higher temperatures compared to c-Co3O4 (CO2 conversion 63%) due to its morphology-induced ∼66 times higher surface basicity. DRIFTS results showed differences in the detected surface species: formate was observed on m-Co3O4 and was proven to contribute to the total methane formation. It was revealed that in CO2 methanation reaction, both bulk and surface properties such as morphology, cobalt oxidation states, acid–base properties, and presence of defect sites directly affect the catalytic performance and reaction mechanism. Furthermore, 1% 5 nm Pt nanoparticles were loaded onto the Co3O4s to check the competitiveness of the catalysts. This study evidences on a cheap noble-metal-free catalyst for CO2 methanation consisting of m-Co3O4 with competitive activity and ∼100% CH4 selectivity.

Impact of Highly Concentrated Alkaline Treatment on Mesostructured Cobalt Oxide for the Oxygen Evolution Reaction

“…[ 39,40 ] However, the band in the region of 1590–1530 cm −1 could be also related to the ν as (COO) vibration mode of formate and acetate species. [ 35,38 ] The presence of these organic impurities was also confirmed by the high‐performance liquid chromatography (HPLC) analysis on 13 m KOH solution. This goes also in line with the presence of CH stretching vibrations in the range of 3000–2800 cm −1 .…”

“…As shown by Figure 2b, the absorption bands at 1427 and 1347 cm −1 reveal the presence of polydentate carbonates (Dν 3 <250), which exhibit high thermal stability. [ 38–40 ] In addition, two more bands are observed at 1550 and 1297 cm −1 that could be attributed to bidentate carbonates (Dν 3 >250). [ 39,40 ] However, the band in the region of 1590–1530 cm −1 could be also related to the ν as (COO) vibration mode of formate and acetate species.…”

CO2heterogeneous hydrogenation to carbon-based fuels: recent key developments and perspectives

“…It should be also noted that CO 2 methanation could be tuned by the valence state of active cobalt species and coordination environment of Co active site. 90,92,93 2.2 Noble metal catalysts Support material modications. Besides non-noble nickelbased catalysts, noble metal (Ru, Rh, and Pt) catalysts generally exhibit higher activity at reduced temperatures, and thus have attracted considerable attention.…”

Pure Ni-Based and Trimetallic Ni-Co-Fe Catalysts for the Dry Reforming of Methane: Effect of K Promoter and the Calcination Temperature

“…The bands in the spectral region from ∼1300 to 1550 cm −1 correspond to the different forms of adsorbed carbonate species [38].…”