Cobalt-Molybdenum Oxides for Effective Coupling of Ethane Activation and Carbon Dioxide Reduction Catalysis

Abstract

This study reports the discovery of CoMoO x moieties with synergistic catalytic roles in C2H6–CO2 catalysis. C2H6–CO2 catalysis occurs through multiple, concomitant catalytic cycles, initiated by the dual cycles of C2H6 activation and CO2 activation, together with an undesired coke deposition cycle. C2H6 activation requires reactive oxygen species that assist with the kinetically relevant C–H bond activation; these oxygen species are generated from the CO2 activation cycle within the reverse water-gas shift (RWGS) reaction. An efficient CO2 activation in the RWGS reaction would retain higher O contents in CoMoO x moieties, leading to more effective kinetically relevant C–H bond activation of C2H6 and oxidation of coke precursors and thus increasing turnovers while mitigating deactivation. This mechanistic insight led us to design CoMoO x moieties, where the Co cation acts as a Lewis acid. Together with a vicinal oxygen vacancy, the Co cation activates CO2 via a Vacancy route through the formation of a kinetically relevant [Co···C­(O)  O··· □vacancy···Mo]‡ transition state, at which the Co interacts with the C and the oxygen vacancy (□vacancy) abstracts the leaving O of CO2. The kinetically coupled cycles lead the ethane conversion rates in dehydrogenation and reforming reactions to both depend directly on the RWGS reaction rates. This mechanistic understanding of rate coupling has led to the design of CoMoO x moieties with dual functionality for effective C2H6–CO2 catalysis.

Highly Efficient Electrochemical Sensing of Acetaminophen by Cobalt Oxide-Embedded Nitrogen-Doped Hollow Carbon Spheres

“…In addition, it reveals that the other low-intensity peaks are associated with the vibration mode of Co 3 O 4 . The E g peak at 436 and A 1 g at 676 cm –1 can be detected, which are related to the octahedral site and crystalline phase of Co 3 O 4 , respectively . Furthermore, the A 1 g peak intensity significantly improved with an increase in the loading amount of CoPc, signifying the enrichment of the crystallinity of the materials, which is in well agreement with the previous XRD measurements.…”

Bimetallic-Derived Catalytic Structures for CO2-Assisted Ethane Activation

“…Figure 2a illustrates the key intermediates and potential reaction pathways for DRE and CO 2 −ODHE, as well as other potential reactions, including direct dehydrogenation of ethane (DHE), reverse water−gas shift (RWGS), and hydrogenolysis. Designing a catalyst with targeted properties poses significant challenges as it involves improving five crucial reaction steps: CO 2 activation, oxygen transfer and supply, activation of C− H/C−C/C�C bonds, carbon scavenging via the C�O bond formation, and desorption of C 2 H 4 and CO. 39,41,42,15,14,43 Balancing these processes is essential to achieve high activity, selectivity, and stability. 14 It remains challenging to control the selective scission of C− H and C−C bonds in alkanes.…”

“…The extent of oxygen’s participation in the transition state leads to the classification of CO 2 -assisted C–H bond activation into the indirect mechanism via a two-step OA mode (II) and the direct mechanism via a one-step σ-MT mode (III or IV). The indirect mode initiates C–H bond activation via oxidative addition, involving either metal atoms (e.g., Pt-based catalysts) , or low-valence metal ions (e.g., Cr δ+ , Mo δ+ , V δ+ , and Co δ+ ) ,, inserting into the C–H bond to form a three-center TS complex, followed by H* elimination by CO 2 -derived O*. Alternatively, the CO 2 -derived O* species can directly participate in C–H bond activation in the transition state, forming a four-center TS complex, followed by the formation of metastable alkoxy species or energetically more favorable species (e.g., OH or H 2 O).…”

Insights into the Molecular Structure of MoOx Catalysts via Static and Transient Raman Experimentation

“…In recent decades, there has been growing interest in the use of supported molybdenum catalysts owing to their outstanding performance in various processes. − Multiple attempts have been made to enhance the reactivity of active molybdenum sites ,,− through modification of their physicochemical properties either by using promoters or a mixed-oxide support phase. However, the simultaneous presence of multiple species with potentially different reactivities may lead to ambiguous interpretations about the link between the synthesis and performance of oxide catalysts.…”