期刊
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
卷 43, 期 32, 页码 15191-15204出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.ijhydene.2018.06.090
关键词
CO2 reduction; Ce-Ni catalyst; g-C3N4-modification; In-situ DRIFTS; Kinetics
资金
- National University of Singapore
- NEA Project [ETRP 1501103, R279000-491-279]
- A*STAR from AME IRG 2017 Project [R279-000-509-305]
- Industry-Academia Cooperation Innovation Fund Projects of Jiangsu Province [BY2016004-09]
- Jiangsu Province Scientific and Technological Achievements into a Special Fund Project [BA2015062, BA2016055, BA2017095]
- Priority Academic Program Development of Jiangsu Higher Education of Jiangsu Higher Education Institutions
- China Scholarship Council
The hydrogenation of CO2 on Ce Ni catalyst modified with g-C3N4 (Ce-Ni-CN) as a sacrificial and protective template was studied by in-situ DRIFTS and Kinetics experiments to investigate the influence of modification on the catalytic activity and selectivity to gain mechanistic insight. After modification, the catalyst showed higher catalytic activity and selectivity. H-2-TPR, CO2-TPD, TEM and XPS confirmed that this modification could enhance the interaction of nickel and ceria and decrease the particle size of nickel, which is in favor of the dissociation of H-2 and adsorption of CO2. The in-situ DRIFTS experiments demonstrated that CO2 is adsorbed on ceria sites, forming carboxylate (CO2 delta-), unidentate carbonate and bicarbonates, which, in turn, react with adsorbed and dissociated H on Ni to produce formate species. Furthermore, adsorbed methoxy species were observed, which are recognized to be intermediates in the methanation process. In-situ transient DRIFTS confirm that the adsorbed CO is not a reaction intermediate, but a by-product, which originates from the decomposition of weak-binding formate species on Ce3+ sites. The unmodified catalyst has more weak-binding formate species, which are more inclined to decompose into CO accounting for the low selectivity. Furthermore, the adsorbed CO on Ce3+ sites cannot react with the adsorbed hydrogen to produce methane. Kinetics studies are consistent with a Langmuir-Hinshelwood type mechanism in which the formation of bicarbonate is the rate-determining step (RDS). 0 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
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