Shielding Protection by Mesoporous Catalysts for Improving Plasma-Catalytic Ambient Ammonia Synthesis

Abstract

Plasma catalysis is a promising technology for decentralized small-scale ammonia (NH₃) synthesis under mild conditions using renewable energy, and it shows great potential as an alternative to the conventional Haber-Bosch process. To date, this emerging process still suffers from a low NH₃ yield due to a lack of knowledge in the design of highly efficient catalysts and the in situ plasma-induced reverse reaction (i.e., NH₃ decomposition). Here, we demonstrate that a bespoke design of supported Ni catalysts using mesoporous MCM-41 could enable efficient plasma-catalytic NH₃ production at 35 °C and 1 bar with >5% NH₃ 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 NH₃ production. The desorbed NH₃ could then diffuse into the ordered mesopores of MCM-41 to be shielded from decomposition due to the absence of plasma discharge in the mesopores of MCM-41, that is, "shielding protection", thus driving the reaction forward effectively. This promising strategy sheds light on the importance of a rational design of catalysts specifically for improving plasma-catalytic processes.