期刊
ACS CATALYSIS
卷 12, 期 16, 页码 9887-9896出版社
AMER CHEMICAL SOC
DOI: 10.1021/acscatal.2c01694
关键词
nitrate reduction; Pt/TiO2; charge density regulation; Zn/Cu doping; density functional theory
资金
- National Natural Science Foundation of China [21903025, 21825301]
- National Key Research and Development Program of China [2018YFA0208602]
- Shanghai Science and Technol- ogy Development Funds [22QA1402900]
This study reveals the complete reaction mechanism and rate-determining steps of nitrate reduction on Pt/TiO2 catalyst. By regulating the charge density of Pt, the dissociation and hydrogenation steps of the reaction can be modified, leading to improved activity. Doping Zn or Cu into TiO2 is proposed as an effective strategy to enhance the nitrate reduction activity.
Rational design of improved catalysts is one of the ultimate goals in catalytic research, the basis of which is clarifying the reaction mechanism and regulation trends. Here, we took nitrate reduction to ammonia as an example and revealed the complete reaction mechanism, rate-determining steps, and charge density regulation trends over Pt/TiO2. The dissociation of the three N-O bonds in NO3- favors the H*-assisted pathway via HONO2* , ONOH* , and HNOH* intermediates, producing the preliminary ammonia source in the form of NH*. Subsequent hydrogenation steps of NH* + H* -> NH2* + * and NH2* + H* -> NH3* + * show the two largest reaction barriers, being the rate-determining steps of the reaction. Further, by regulating the Pt charge density, we showed that all of the dissociation steps are slightly deactivated, whereas the hydrogenation steps, particularly those involving NH* and NH2*, are apparently promoted as positive charges accumulate on Pt particles. Accordingly, doping of Zn or Cu into TiO2 was proposed and furthermore verified as an effective strategy to improve the nitrate reduction activity. Such a promotional effect was attributed to the reduced H* adsorption energy on the metal surface as it became positively charged, manifesting itself as a general principle in boosting the hydrogenation activity.
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