Typical assumptions made in surface catalysis modeling are that the surface structures are well-defined and may not be changed during reaction, coupled with neglected adsorbate-adsorbate interactions. However, the catalyst surface structures and the behavior of surface adsorbates are substantially more complex under realistic conditions than we assumed. In this talk, I will present our attempts to understand the effect of adsorbate-adsorbate interactions and competitive adsorption on the reaction kinetics of methanol synthesis from CO2 hydrogenation over Cu and PdIn catalysts. In order to reveal the effect of surface spectating formates on the reaction kinetics of methanol formation, energetics of the CO2 hydrogenation pathway over clean and one/two formate pre-adsorbed Cu(211) were obtained with density functional theory (DFT) calculations, and these energetics were further employed for the microkinetic modeling.1 We found that the interactions between formates and the intermediates and transition-states involved in the reaction pathway result in changes of the formation rates of methanol, as shown in Figure 1. Over PdIn, we found that competitive adsorption between HCOO and CO over PdIn catalyst surfaces under reaction conditions will influence the selectivity between methanol and CO formation.2 Our work shows that, in order to obtain better understandings on the kinetics of surface reactions and to design more effective catalysts, it is essential to consider the interactions between surface adsorbates while performing DFT calculations and microkinetic studies.

Influence of surface adsorbate interactions on the reaction kinetics of methanol synthesis from CO2 hydrogenation

256th National Meeting (2018)

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