期刊
ACS CATALYSIS
卷 10, 期 5, 页码 3264-3273出版社
AMER CHEMICAL SOC
DOI: 10.1021/acscatal.9b04239
关键词
In2O3 catalysts; crystal phase transition; reverse water gas shift reaction; oxygen vacancy; DFT simulations; in situ XRD
资金
- National Key Research and Development Program of China [2016YFB0600902-4]
- National Natural Science Foundation of China [21902019]
- Fundamental Research Funds for Central Universities [DUT18RC(3)057]
- Pennsylvania State University
- Rice University
Understanding the structure-catalytic activity relationship is crucial for developing new catalysts with desired performance. In this contribution, we report the performance of In2O3 with different crystal phases in the reverse water gas shift (RWGS) reaction, where we observe changing activity induced by a phase transition under reaction conditions. Cubic In2O3 (c-In2O3) exhibits a higher RWGS rate than the hexagonal phase (h-In2O3) at temperatures below 350 degrees C because of its (1) enhanced dissociative adsorption of H-2, (2) facile formation of the oxygen vacancies, and (3) enhanced ability to adsorb and activate CO2 on the oxygen vacancies, as suggested both experimentally and computationally. Density functional theory results indicate that the surface oxygen arrangement on the cubic polymorph is key to rapid H-2 adsorption, which facilitates oxygen vacancy formation and subsequent CO2 adsorption to yield high RWGS reactivity. At 450 degrees C and above, the activity of h-In2O3 increases gradually with time on stream, which is caused by a phase transition from h-In2O3 to c-In2O3. In situ X-ray diffraction experiments show that h-In2O3 is first reduced by H-2 and subsequently oxidized by CO2 to c-In2O3. These findings highlight the importance of the crystal phase in the catalytic RWGS reaction and provide a new dimension for understanding/designing RWGS catalysts.
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