A Mössbauer spectroscopic study of cobalt-iron molybdates

Sr2Fe2−Mo O6− perovskite as an anode in a solid oxide fuel cell: Effect of the substitution ratio

“…It agrees with the common knowledge that the activity of perovskite depends on its B site metals [17]. Moreover, the Fe 2+ /Fe 3+ pair is reported to play an important role in the oxidation of propane [25]. The substitution of Fe with Mo could generate or stabilize Fe 2+ ion, and SFMO with a higher Fe 2+ content is expected to possess a higher activity.…”

The role of cationic additions in molybdate multi-component catalysts

“…No The quadrupole splitting values of Fe 2+ in βFeMoO 4 phase are higher than those of FeMoO 4 , obtained in the same phase. These values are similar to those obtained for Fe x Co 1−x MoO 4 having low and medium iron contents [14].…”

“…The Fe 3+ concentration remains constant when increasing the temperature and the period of heat treatment, which clearly indicates a dissolution limit of Fe 3+ in CoMoO 4 . This assertion is supported by electric conductivity measurements [14]; CoMoO 4 is low conducting material and the addition of iron leads to a considerable increase of its conductivity. Since the substitution of Co 2+ by Fe 2+ is not accompanied by a gain of electric charges, thus only dissolved Fe 3+ ions are responsible for the enhancement of the electric conductivity.…”

“…All the Mössbauer spectra of annealed Fe 2 (MoO 4 ) 3 +MgMoO 4 exhibit one Fe 3+ doublet and its attribution depend on the heating period, but the ferric species concentration is independent from this factor. The Mössbauer spectrum recorded for the solid annealed during 2 h, exhibits one doublet Fe 3+ with a high value of quadrupole splitting comparing to the one obtained for FeMoO 4 or Fe x Co 1−x MoO 4 [14], thus indicating the dissolution of this species in the framework. This species tends to disappear when the annealing period increases to reach the one of ferric molybdate.…”

Morphology and chemical state of Co?Mo catalysts for growth ofBsingle-walled carbon nanotubes vertically aligned on quartz substrates

“…Besides Co-Mo systems, other X-Y bimetallic systems (X = Fe, Co, and Ni; Y = Ti, Cr, Mo, W, and Al) [59][60][61][62][63][64][65][66][67] should act as excellent catalysts to the SWNT growth or other reactions due to similar mechanism. Here, X is a VIII-group element known as monometallic catalysts for the SWNT growth, and Y is mainly an IVB-, VB-, and VIBgroup element capable of forming stable high-valent oxides due to their vacant d orbital.…”