Applications of tricobalt tetraoxide

Tricobalt tetraoxide, also knownas Cobalt(II,III) oxide is a black antiferrimagnetic solid. Our Co3O4 is a powder with a particle size of <10 μm and a cobalt concentration between 71-74%. A high melting point of 895 °C (dec.) indicates that Co3O4 can with stand elevated temperatures without decomposing, making it suitable for high-temperature applications such as heterogeneous catalysis in industrial processes. Co3O4 is also widely used in the battery industry as a precursor to fabricate cathode materials, such as lithium cobalt oxide and lithium nickel manganese cobalt oxide, for Li-ion batteries.

Morphology-dependent nanocatalysis: tricobalt tetraoxide

The catalytic properties of metal oxides are fundamentally linked to the arrangements of surface metal and oxygen atoms, which could be practically mediated by tuning the size and shape of the oxide particles at the nanometer level. The size effect of oxide nanoparticles has been well documented both experimentally and theoretically: Lowering the size of oxide particles to few nanometers, favorably less than 10 nm, alters the geometric and electronic structure of the surface atoms and thus increases the number of active sites that typically locate at the edges, corners and steps. In this mini-review article, we took tricobalt tetraoxide as an example to show the remarkable impact of the oxide particle shape on the catalytic property. We briefly summarized the significant progress on shape engineering of tricobalt tetraoxide nanoparticles, followed by analyzing their catalytic performance in oxidation reactions, which are closely associated with the coordination patterns of surface cobalt and oxygen atoms. At the last section, we presented our perspectives on the further development of nanostructured cobalt oxides and emphasized the vital role of the configurations of the surface cobalt and oxygen atoms induced by the particle shape during catalysis. tricobalt tetraoxide nanoparticles are usually prepared by aqueous-phase precipitation and hydrothermal and/ or solvothermal synthesis.[1]

Tuning the shape of tricobalt tetraoxide nanoparticles has been verified to significantly alter the redox feature and the catalytic property. This morphology-dependent nanocatalysis is frequently interpreted with respect to the preferential exposure of the reactive crystal facets that allowed a dense population of active sites for catalysis. In particular, the rod-shaped Co3O4 nanoparticles, typically exposing a substantial fraction of the (110) facet, are featured by the coexistence of tetrahedral Co2+ and octahedral Co3+ sites that are intimately linked to the catalytic activity toward oxidation reactions. Continuous accumulation of experimental data over various tricobalt tetraoxide nanostructures has gradually clarified that identifying the active sites requires to consider the restructuring of the nanoparticles under the reaction conditions. Moreover, the synergistic effect between the reactive facet and its neighboring less-active facets could not be simply ruled out.

Porous cerium-doped tricobalt tetraoxide dodecahedrons

Hydrogen sulfide (H2S), recognized as a highly toxic gaseous compound, primarily originates from the anaerobic microbial decomposition of organic substrates in petroleum reservoirs, wastewater treatment facilities, and natural anaerobic environments. Among p-type oxides, tricobalt tetraoxide (Co3O4) is a typical member, featuring variable valence states of Co ions (Co2+, Co3+). This endows it with high catalytic activity and oxidizing ability toward reducing gases (especially H2S), making Co3O4 exhibit excellent gas-sensing performance and rendering it one of the most widely studied gas-sensing materials currently. However, previous reports indicate that for materials with identical morphology, the sensitivity of p-type semiconductors is proportional to the square root of that of n-type semiconductors. Like other p-type oxides, improving the response to target gases remains a critical challenge for the advancement of tricobalt tetraoxide gas-sensing materials. Building upon the aforementioned considerations, we propose a novel strategy that harnesses the synergistic effects of Ce doping and MOFs-derived high porosity to synthesize Ce-doped Co3O4 porous dodecahedrons, which feature surface-abundant oxygen species and enhanced H2S sensitivity. The optimal sensor displayed the highest sensitivity to 1–100 ppm H2S at 220 °C. Furthermore, the improvements in gas-sensing performance and the underlying mechanism of Ce-doped tricobalt tetraoxide -based H2S sensors were systematically studied through experimental characterization combined with first-principles calculations. Finally, a new regression model was constructed to predict H2S concentration.[2]

In conclusion, we have successfully designed an efficient hydrogen sulfide (H2S) gas sensor fabricated using cerium (Ce)-doped tricobalt tetraoxide derived from metal-organic framework (MOF) self-sacrificial templates. The obtained dodecahedron nanomaterials, featuring abundant pore structures, exhibit a higher specific surface area (30.57 m2/g) and surface-adsorbed oxygen ratio (17.88 %) compared to previously reported MOF derivatives. Particularly, the H2S gas sensor based on 3 at.% Ce-Co3O4 exhibits faster recovery kinetics and a lower detection limit than earlier resistive H2S sensors. The enhanced H2S sensing performance can be primarily ascribed to the permeable porous structure, abundant surface chemisorbed oxygen, and increased Co3+/Co2+ ratio resulting from Ce doping. Furthermore, density functional theory (DFT) calculations indicate that doping Ce not only increases the adsorption energy of tricobalt tetraoxide for H2S, but also promotes charge transfer between H2S and the material, explaining the superior H2S detection performance of Ce-Co3O4 over pure Co3O4 from an atomic perspective. Notably, Ce doping is more effective than other modification methods in enhancing the adsorption energy of H2S on Co3O4.

References

[1]Shen, W. (2021). Morphology-dependent nanocatalysis: tricobalt tetraoxide. Research on Chemical Intermediates, 47, 195–209. https://doi.org/10.1007/s11164-020-04344-z

[2]Huang, Long et al. “Metal-organic framework-derived porous cerium-doped tricobalt tetraoxide dodecahedrons for efficient detection of hydrogen sulfide.” Journal of colloid and interface science vol. 700,Pt 3 (2025): 138567. doi:10.1016/j.jcis.2025.138567