| AVS 64th International Symposium & Exhibition | |
| Fundamental Discoveries in Heterogeneous Catalysis Focus Topic | Thursday Sessions |
| Session HC+SS-ThA |
| Session: | Combined Experimental and Theoretical Explorations of the Dynamics of Heterogeneously Catalyzed Reactions |
| Presenter: | Fanglin Che, University of Toronto, Canada |
| Authors: | F.L. Che, University of Toronto, Canada J. Gray, Washington State University S. Ha, Washington State University J.-S. McEwen, Washington State University |
| Correspondent: | Click to Email |
According to the Annual Energy Outlook, natural gas production in the U.S. is projected to continue rising through 2040. To make the most of this abundant natural resource and at the same time reduce emissions of harmful greenhouse gases it is imperative that we fully understand the catalytic reactions which are used in methane processing – particularly methane steam reforming (MSR). MSR is our reaction of interest also because the conversion of methane to syngas greatly affects the charge-transfer chemistry and consequently influences the SOFCs' performance. There are two significant issues facing MSR: (i) Coke formation; (ii) High temperatures of above 900 K. To address these issues, we are interested in the effect of an electric field on this process. [1,2]
Based on a field-dependent microkinetic model of the MSR reaction and corresponding experimental evidence, we find that a positive electric field can significantly enhance the methane conversion and reduce the formation of coke over a pure Ni surface. [3-8] The reason for such an improvement can be correlated with the fact that a positive field polarizes the Ni surface with a partial positive charge, which assists the first C-H bond cleavage of a methane molecule. [9] Changing the oxygen vacancy concentration and increasing the applied electric field value affects the charge of the Ni cluster in a Ni/YSZ cermet as well. Interestingly, we find that the C-H bond cleavage of methane becomes more favorable as the Ni cluster becomes more positively charged. We also find that the carbon complex resulting from the dissociation of a CH molecule at the triple phase boundary region of a Ni/YSZ cermet results in a more positively charged Ni cluster, which facilitates the cleavage of the first C-H bond in methane as compared to when the carbon complex is absent. This indicates that the initial carbon species resulting from the decomposition of methane assists in the first C-H bond cleavage of a methane molecule rather than the formation of coke that poisons the Ni-based catalyst. Overall, this work provides valuable information for a new design of electrochemical systems to enhance methane activation.
[1] Stüve, E. M. Chem. Phys. Lett.2012,519, 1.
[2] Kreuzer, H. J. Surf. Sci. Anal.2004,36, 372.
[3] Che, F. et al., Catal. Sci. Technol.2014, 4020.
[4] Che, F. et al., Phys. Chem. Chem. Phys.2014,16, 2399.
[5] Che, F. et al., J. Catal.2015,332, 187.
[6] Che, F. et al., Appl. Catal. B2016,195, 77.
[7] Che, F. et al., ACS Catal.2017,7, 551.
[8] Che, F. et al., ACS Catal.2017,under review.
[9] Che, F. et al., Angew. Chem. Int. Ed.2017,129, 3611.