First principles studies of CO2 activation and reduction over indium oxide and copper surfaces
Doktorsavhandling, 2021

Catalytic recycling of carbon dioxide (CO2) to added-value chemicals, such as methanol (CH3OH), have been proposed as a possible path for sustainable production of fuel and chemicals, in addition to providing a route to mitigate anthropogenic carbon emissions. Several catalytic systems are known to be active for conversion of CO2 to methanol, Cu/ZnO/Al2O3 being the main industrial catalyst for the process. This catalyst is, however, known to deactivate over time due to copper sintering. In recent years an alternative In2O3/ZrO2 catalyst has attracted attention, thanks to its reported high selectivity, activity and durability.

In this thesis, the activation and reduction of CO2 over Cu(100) and In2O3(110) are investigated from first principles-based calculations and simulations. Reaction intermediates and thermodynamic calculation of surface energy, coupled with theoretical X-ray photoelectron spectroscopy and mean-field microkinetic modeling, are utilized to describe and rationalize surface conditions and reaction mechanisms for the dissociative adsorption of CO2 on Cu(100) and for its reduction to CH3OH on In2O3(110).

The oxidation process of Cu(100) by dissociative CO2 adsorption is found to be controlled by step sites. The role of the step is found to be two-fold, lowering the dissociation energy and simultaneously providing physical separation of the products. Upon reaction, the surface is found to oxidize from the pristine to a disordered p(2×2) oxygen overlayer to a reconstructed (2√2×√2)R45-missing row structure.

Dissociative adsorption of H2 is investigated on In2O3(110) and In2O3(111). The adsorption is found to be facile, and both surfaces are predicted to be hydroxylated at typical methanol synthesis reaction conditions. CO2 reduction to CH3OH on the hydrogen covered In2O3(110) is investigated along a formate (HCOO) mediated mechanism, where the rate controlling step is found to be formation of H2CO+OH. The role of the competing Reverse Water Gas Shift reaction is also evaluated.

The presented findings exemplify the significance of describing catalytic systems under thermodynamically relevant reaction conditions. Additionally, the results provide some understanding and insight on the mechanistic aspects of CO2 activation and reduction to added-value chemicals.

CO2 reduction

indium oxide

methanol conversion

copper surface

Heterogeneous catalysis

Density Functional Theory

online (Password: 372271)
Opponent: Prof. Karoliina Honkala, Department of Chemistry, University of Jyväskylä

Författare

Alvaro Posada Borbon

Chalmers, Fysik, Kemisk fysik

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Hydrogen adsorption on In2O3(111) and In2O3(110)

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CO2 adsorption on hydroxylated In2O3(110)

Physical Chemistry Chemical Physics,; Vol. 21(2019)p. 21698-21708

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Steps Control the Dissociation of CO2 on Cu(100)

Journal of the American Chemical Society,; Vol. 140(2018)p. 12974-12979

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A first-principles based microkinetic study of CO2 reduction to CH3OH over In2O3(110)

Catalysts, like the ones controlling the exhaust of modern cars, have the ability of transforming harmful gases into innocuous or even useful products. Catalytic recycling of carbon dioxide (CO2) to methanol, has been proposed as a possible path for sustainable production of fuel, providing a route to reduce carbon emissions produced by humans.

Methanol can presently be synthesized from carbon dioxide over a copper-based catalyst. However, under working conditions, the copper-based catalyst becomes rapidly inactive. In recent years, an indium oxide-based catalyst has attracted attention, as an alternative to the
copper-based catalyst. However, the reasons behind it's performance are not well understood. Understanding the chemical reaction that happens on the catalyst surface and the material properties that make it possible, can aid further improving the catalytic system. This kind of
understanding can be attained from theoretical investigations by computational modeling of the catalyst and reactions.

In this thesis, the initial oxidation of copper by CO2 reacting at its surface is investigated computationally. We find that the oxidation of copper reduces its ability to react with CO2. Moreover, we propose a mechanism through which the initial oxidation occurs. Additionally, we  investigate a chemical mechanism for CO2 conversion to methanol on an indium oxide  surface. We find that the chemical properties of the indium oxide surface change during  reaction and are likely one factor why indium oxide can transform CO2 into methanol. 
Hopefully, the work presented here will aid the development of catalyst designed for conversion of carbon dioxide to methanol.

Atomär design av katalysatorer

Knut och Alice Wallenbergs Stiftelse, 2016-01-07 -- 2021-06-30.

Ämneskategorier

Fysik

Kemi

Infrastruktur

C3SE (Chalmers Centre for Computational Science and Engineering)

ISBN

978-91-7905-441-0

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4908

Utgivare

Chalmers tekniska högskola

online (Password: 372271)

Online

Opponent: Prof. Karoliina Honkala, Department of Chemistry, University of Jyväskylä

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Senast uppdaterat

2021-02-18