| AVS 65th International Symposium & Exhibition | |
| Fundamental Discoveries in Heterogeneous Catalysis Focus Topic | Wednesday Sessions |
| Session HC+SS-WeA |
| Session: | Theory and Dynamics of Heterogeneously Catalyzed Reactions |
| Presenter: | Richard van Lent, Leiden University, Netherlands |
| Authors: | R. van Lent, Leiden University, Netherlands A.J. Walsh, DIFFER, Netherlands M.A. Gleeson, DIFFER, Netherlands L.B.F. Juurlink, Leiden University, Netherlands |
| Correspondent: | Click to Email |
Catalytically converting CO2 into renewable fuels is a promising avenue that addresses the current fuel and energy storage challenges. Depending on the process, conversion of CO2 may involve initial breaking of the OC=O bond. If so, this highly endothermic step is likely rate limiting to the overall process. Ultra‑high vacuum (UHV) research on well-defined surfaces can provide fundamental insight into such processes, e.g. how dissociation may be aided by internal energy in CO2, the metal’s identity and the surface structure.
Internal energy has been shown to promote the highly activated dissociative adsorption of CO2 on Ni(100) [1]. Rovibrationally state-resolved measurements for CH4 on Ni(100) have shown that excitation of the ν3 antisymmetric stretch vibration has a promoting effect that approximately equals kinetic energy for Ni(100) surfaces [2,3]. For other metal surfaces and CH4 vibrations, the relative efficacy of vibrational and kinetic energies varies between 0.4 and 1.4 [2].
To start unravelling how CO2 dissociates on a surface, we combine standard supersonic molecular beam techniques with high resolution continuous wave (cw) IR laser excitation. We study the effect of ν3 antisymmetric stretch excitation of CO2 on dissociative adsorption on a Ni(711) surface.
For excitation, we use a 3.9-4.6 μm single mode optical parametric oscillator (OPO). The OPO is frequency-stabilized by locking onto the derivative of the lamb dip of the specific rovibrational transition of interest. Frequency-stabilized IR radiation is crossed with a supersonic molecular beam that impinges onto the cleaned Ni(711) surface under UHV conditions. We use methods to determine absolute reactivities for CO2 molecules with and without laser excitation. We extract rovibrational state-dependent absolute sticking probabilities as a function of kinetic energy. From this data, we determine the relative efficacy of vibrational and kinetic energy in overcoming the large activation barrier to dissociation.
[1] M. P. D’Evelyn, A. V. Hamza, G. E. Gdowski, and R. J. Madix, Surf. Sci.167, 451 (1986).
[2] L. B. F. Juurlink, D. R. Killelea, and A. L. Utz, Prog. Surf. Sci. 84, 69 (2009).
[3] B. L. Yoder, R. Bisson, and R. D. Beck, Sci. 329 , 553 (2010).