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TiO 2 supported catalysts have been widely studied for the selective catalytic reduction (SCR) of NO x ; however, comprehensive understanding of synergistic interactions in multi-component SCR catalysts is still lacking. Herein, transition metal elements (V, Cr, Mn, Fe, Co, Ni, Cu, La, and Ce) were loaded onto TiO 2 nanoarrays via ion-exchange using protonated titanate precursors. Amongst these catalysts, Mn-doped catalysts outperform the others with satisfactory NO conversion and N 2 selectivity. Cu co-doping into the Mn-based catalysts promotes their low-temperature activity by improving reducibility, enhancing surface Mn 4+ species and chemisorbed labile oxygen, and elevating the adsorption capacity of NH 3 and NO x species. While Ce co-doping with Mn prohibits the surface adsorption and formation of NH 3 and NO x derived species, it boosts the N 2 selectivity at high temperatures. By combining Cu and Ce as doping elements in the Mn-based catalysts, both the low-temperature activity and the high-temperature N 2 selectivity are enhanced, and the Langmuir–Hinshelwood reaction mechanism was proved to dominate in the trimetallic Cu–Ce–5Mn/TiO 2 catalysts due to the low energy barrier.
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Mechanistic insights into C2 and C3 product generation using Ni 3 Al and Ni 3 Ga electrocatalysts for CO 2 reduction
Thin films of Ni 3 Al and Ni 3 Ga on carbon solid supports have been shown to generate multi-carbon products in electrochemical CO 2 reduction, an activity profile that, until recently, was ascribed exclusively to Cu-based catalysts. This catalytic behavior has introduced questions regarding the role of each metal, as well as other system components, during CO 2 reduction. Here, the significance of electrode structure and solid support choice in determining higher- versus lower-order reduction products is explored, and the commonly invoked Fischer–Tropsch-type mechanism of CO 2 reduction to multi-carbon products is indirectly probed. Electrochemical studies of both intermetallic and non-mixed Ni–Group 13 catalyst films suggest that intermetallic character is required to achieve C2 and C3 products irrespective of carbon support choice, negating the possibility of separate metal sites performing distinct yet complementary roles in CO 2 reduction. Furthermore, Ni 3 Al and Ni 3 Ga were shown to be incapable of generating higher-order reduction products in D 2 O, suggesting a departure from accepted mechanisms for CO 2 reduction on Cu. Additional routes to multi-carbon products may therefore be accessible when developing intermetallic catalysts for CO 2 electroreduction.
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- Award ID(s):
- 1800400
- PAR ID:
- 10106176
- Date Published:
- Journal Name:
- Faraday Discussions
- Volume:
- 215
- ISSN:
- 1359-6640
- Page Range / eLocation ID:
- 192 to 204
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/c8fd00177d
