Shielding effect of mesoporous catalysts for plasma-enhanced catalytic synthesis of ammonia under ambient conditions Yaolin Wang 1 , Wenjie Yang 2 , Shanshan Xu 3 , Jia Ding 2 , Shufang Zhao 2 , Guoxing Chen 4 , Christopher Hardacre 3 , Xiaolei Fan 3 , Jun Huang 2 and Xin Tu 1 1 University of Liverpool, UK, 2 University of Manchester, UK, 3 University of Sydney, Australia Plasma catalysis is a promising technology for decentralised ammonia (NH 3 ) synthesis under mild conditions using renewable energy and shows great potential as an alternative to the conventional Haber-Bosch process 1 . To date, this emerging process still suffers from a low NH 3 yield due to limited knowledge in the design of highly efficient catalysts and the in situ plasma-induced reverse reaction (i.e., NH 3 decomposition). Here we show that a bespoke design of supported Ni catalysts using mesoporous MCM-41 could enable efficient plasma- catalytic NH 3 production at 35 °C and 1 bar with >5% NH 3 yield at 60 kJ/L. Specifically, the Ni active sites were deliberately deposited on the external surface of MCM-41 to enhance plasma-catalyst interactions and thus NH 3 production. The gradient NH 3 concentration across the mesoporous framework enabled the formed NH 3 to diffuse into the ordered mesopores of MCM-41, where is was shielded from the plasma-induced reverse reaction (NH 3 decomposition) due to the absence of plasma discharge in the mesopores, that is, shielding protection, thus driving the reaction forward effectively.A unique integrated plasma/FTIR cell for in situ probing of plasma-induced surface reactions over different Ni/MCM-41 catalysts, together with comprehensive catalyst characterisation and plasma diagnostics, was used to clearly demonstrate and elucidate this catalytic mechanism for enhanced plasma-catalytic ammonia synthesis under ambient conditions.This strategy sheds light on the importance of rational design of tailored catalysts for plasma catalysis, which is critical to advancing the development of plasma- catalytic systems toward practical adoption 2 . References 1. Y. Wang, M. Craven, X. Yu, J. Ding, P. Bryant, J. Huang, X. Tu, ACS Catal . 2019 , 9 , 10780-10793. 2. Y. Wang, W. Yang, S. Xu, S. Zhao, G. Chen, A. Weidenkaff, C. Hardacre, X. Fan, J. Huang, X. Tu, J. Am. Chem. Soc . 2022 , 144 , 12020-12031.
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