Simultaneous Activation of CH4 and CO2 for Concerted C-C Coupling at the Oxide-Oxide Interfaces
- UNIVERSITY PROGRAMS
- Tianjin University
- BATTELLE (PACIFIC NW LAB)
- Southern Illinois University
Catalytic conversion of CO2 and CH4 to value-added platform chemicals via the direct C-C coupling provides one of the most effective routes that not only address global climate change but also alleviate the dependency on traditional fossil fuels. Herein, three oxide-on-oxide catalysts that can realize direct C-C coupling on the basis of simultaneous activation of CH4 and CO2 were investigated using density functional theory (DFT) calculations. With the formation of oxide-on-oxide interfacial sites between the substrate (In2O3) and dispersed oxides ((ZnO)3, (ZrO2)3, or Ga2O3), it is found that CO2 can be activated at the defective site of In2O3 while the C-H bond of CH4 can be simultaneously activated at the M-O pair of the supported metal oxide. In contrast to the Eley-Rideal mechanism that C-C coupling of CO2 and CH3 stabilized on Zn-doped ceria follows, the formation of a Zn-C-C-O transition state at the active centers originates from a Langmuir-Hinshelwood mechanism where the activated CO2 also enhances the dissociative adsorption of CH4. There is a linear relationship between the C-C coupling reaction energy/activation barrier and CH4 dissociation energy. The results indicate that dissociative adsorption of CH4 plays a dominant role in the direct C-C coupling, whereas the adsorption/activation of CO2 is less significant. DFT calculation results of CH4 and CO2 to acetic acid on the (ZnO)3/In2O3 catalyst surface indicates that the C-C coupling step is the kinetically most relevant step. Compared with Ga2O3/In2O3 and (ZrO2)3/In2O3 catalyst surfaces, (ZnO)3/In2O3(110) is more active for the acetic acid formation. The present work provides new mechanistic insights into the direct C-C coupling of CH4 and CO2, which would be useful to design more efficient catalyst.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1525307
- Report Number(s):
- PNNL-SA-138001
- Journal Information:
- ACS Catalysis, Journal Name: ACS Catalysis Journal Issue: 4 Vol. 9
- Country of Publication:
- United States
- Language:
- English