Co nanoparticles of well-defined size were synthesized by temperature-controlled injection of Co2(CO)8 into dichlorobenzene. After intercalation into mesoporous MCF-17 and temperature-programmed oxidation, Co3O4/MCF-17 model catalysts were obtained with cobalt oxide particle sizes varying between 3.5 and 12.2 nm. We demonstrate here the occurrence of a distinct particle size effect for the CO oxidation. Maximum reaction rates of about 0.77 nm–2 s–1 at 150 °C were observed for Co3O4 particles with a size in the range of 5 to 8 nm. The reaction rates decreased for either smaller or larger sizes. X-ray photoelectron spectroscopy allowed establishing a clear correlation between the Co3+ trivalent oxidation state and the CO oxidation rate.

Bimetallic CoCu model catalysts were investigated for the synthesis of higher alcohols using catalytic CO hydrogenation according to the Fischer−Tropsch technology. Emphasis was placed on revealing the influence of the activation conditions. Accordingly, catalyst precursors were activated in argon, hydrogen, syngas (CO/H 2 ), and CO under atmospheric conditions and at elevated temperatures (370 °C). All catalyst precursors were prepared via oxalate coprecipitation in the absence of a classic support. Alcohol selectivities between 30 and ∼40% (up to ∼50% for the sum of alcohols and alkenes) were obtained with an Anderson−Schulz−Flory (ASF) chain lengthening probability maximizing the slate up to C 6 . Detailed catalysis and characterization studies were performed using a Co 2 Cu 1 catalyst composition. The catalytic performances of the H 2 -and syngas-activated Co 2 Cu 1 catalyst were similar. While the CO-activated catalyst shows significantly higher catalytic activity and ASF chain lengthening probability, the alcohol selectivities are lower than those of H 2 -or syngas-activated ones. All catalysts required time on stream for several hours to achieve steady-state catalytic performance. Co 2 Cu 1 catalysts were characterized by temperature-programmed decomposition (TPDec), in situ N 2 physisorption (Brunauer−Emmett−Teller), transmission electron microscopy (TEM), and in situ X-ray photoelectron spectroscopy (XPS). The data indicate major restructuring occurs during activation. An "onion-like" graphitic carbon shell was observed via TEM for the CO-activated Co 2 Cu 1 catalyst, which probably originated mainly from the Boudouard reaction (2CO + [ ] ad → C ad + CO 2 ). This interpretation is in accordance with the TPDec profiles and XPS results. The latter also indicates that syngas and CO activation lead to higher than nominal Co/Cu surface ratios. The surface segregation of Co in the presence of CO atmospheres is interpreted on the basis of Co@Cu core−shell structured particles.

Magnetic cobalt-based nanoparticles (NPs) with homogeneous size were selectively cast inside the channel of multiwalled carbon nanotubes (CNTs). The proposed synthesis method allows for filling only the CNTs channel with an unprecedented high density. The CNTs act as “nanoreactors” and provide protection against oxidation.