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Metastable Corundum-Type In2O3: Phase Stability, Reduction Properties, and Catalytic Characterization

Köck, Eva-Maria and Kogler, Michaela and Grünbacher, Matthias and Zhuo, Chen and Thalinger, Ramona and Schmidmair, Daniela and Schlicker, Lukas and Gurlo, Aleksander and Penner, Simon (2016):
Metastable Corundum-Type In2O3: Phase Stability, Reduction Properties, and Catalytic Characterization.
In: Journal of Physical Chemistry C, American Chemical Society, Washington, USA, pp. 15272-15281, 128, (28), ISSN 1932-7447,
DOI: 10.1021/acs.jpcc.6b04982,
[Online-Edition: https://pubs.acs.org/doi/10.1021/acs.jpcc.6b04982],
[Article]

Abstract

The phase stability, reduction, and catalytic properties of corundum-type rhombohedral In2O3 have been comparatively studied with respect to its thermodynamically more stable cubic In2O3 counterpart. Phase stability and transformation were observed to be strongly dependent on the gas environment and the reduction potential of the gas phase. As such, reduction in hydrogen caused both the efficient transformation into the cubic polymorph as well as the formation of metallic In especially at high reduction temperatures between 573 and 673 K. In contrast, reduction in CO suppresses the transformation into cubic In2O3 but leads to a larger quantity of In metal at comparable reduction temperatures. This difference is also directly reflected in temperature-dependent conductivity measurements. Catalytic characterization of rh-In2O3 reveals activity in both routes of the water-gas shift equilibrium, which gives rise to a diminished CO2-selectivity of similar to 60% in methanol steam reforming. This is in strong contrast to its cubic counterpart where CO2 selectivities of close to 100% due to the suppressed inverse water-gas shift reaction, have been obtained. Most importantly, rh-In2O3 in fact is structurally stable during catalytic characterization and no unwanted phase transformations are triggered. Thus, the results directly reveal the application-relevant physicochemical properties of rh-In2O3 that might encourage subsequent studies on other less-common In2O3 polymorphs.

Item Type: Article
Erschienen: 2016
Creators: Köck, Eva-Maria and Kogler, Michaela and Grünbacher, Matthias and Zhuo, Chen and Thalinger, Ramona and Schmidmair, Daniela and Schlicker, Lukas and Gurlo, Aleksander and Penner, Simon
Title: Metastable Corundum-Type In2O3: Phase Stability, Reduction Properties, and Catalytic Characterization
Language: English
Abstract:

The phase stability, reduction, and catalytic properties of corundum-type rhombohedral In2O3 have been comparatively studied with respect to its thermodynamically more stable cubic In2O3 counterpart. Phase stability and transformation were observed to be strongly dependent on the gas environment and the reduction potential of the gas phase. As such, reduction in hydrogen caused both the efficient transformation into the cubic polymorph as well as the formation of metallic In especially at high reduction temperatures between 573 and 673 K. In contrast, reduction in CO suppresses the transformation into cubic In2O3 but leads to a larger quantity of In metal at comparable reduction temperatures. This difference is also directly reflected in temperature-dependent conductivity measurements. Catalytic characterization of rh-In2O3 reveals activity in both routes of the water-gas shift equilibrium, which gives rise to a diminished CO2-selectivity of similar to 60% in methanol steam reforming. This is in strong contrast to its cubic counterpart where CO2 selectivities of close to 100% due to the suppressed inverse water-gas shift reaction, have been obtained. Most importantly, rh-In2O3 in fact is structurally stable during catalytic characterization and no unwanted phase transformations are triggered. Thus, the results directly reveal the application-relevant physicochemical properties of rh-In2O3 that might encourage subsequent studies on other less-common In2O3 polymorphs.

Journal or Publication Title: Journal of Physical Chemistry C
Volume: 128
Number: 28
Publisher: American Chemical Society, Washington, USA
Uncontrolled Keywords: WATER-GAS-SHIFT; INDIUM OXIDE; REFORMING ACTIVITY; TEMPERATURE; POLYMORPHS; KINETICS; NANOCRYSTALS; SELECTIVITY; TRANSITION; CHEMISTRY
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Dispersive Solids
Date Deposited: 22 Aug 2018 14:16
DOI: 10.1021/acs.jpcc.6b04982
Official URL: https://pubs.acs.org/doi/10.1021/acs.jpcc.6b04982
Funders: FWF (Austrian Science Foundation): FOXSI F4503-N16, DFG: SPP 1415, GU 992/12-1
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