Unlocking Efficient Synergistic Plasma-Catalyst Ammonia Synthesis: System Optimization and Catalyst Support Screening

Abstract

Plasma catalysis for ammonia synthesis technology exhibits significant development potential, and improving the synergistic interaction between plasma and catalyst is a challenging research focus. However, current research focuses on efficient catalyst formulation design, but studies on catalyst support material screening and reactor performance optimization are lacking. Therefore, this study first enhanced the ammonia synthesis capability of the reactor and found that the 5 cm ground electrode and center plasma catalysis (CPC) coupling were the optimal system configurations. Support screening tests showed that higher dielectric properties and highly ordered interconnecting pores are crucial to achieving high ammonia concentration production. The SBA-15 (best material) filled system showed the highest reduced electric field (122.97 Td), with a more significant number of high-energy electrons and an average electron energy of up to 3.93 eV. Possible enhanced mechanisms for ammonia synthesis on SBA-15 include: (1) promoting the excitation dissociation process of feed gas in the gas phase and the activation process on the material surface and (2) using ordered tubular channels to suppress the occurrence of plasma-induced reverse reactions. By adjusting the flow rate, ammonia concentration as high as 11737 ppm was achieved, 4.58 times higher than the empty tube. The highest achieved synthesis rate was 5337 μmol/gcat/h, and the energy yield was 1.04 gNH3 /kWh. Additionally, the study indicated that a nitrogen-rich environment is more beneficial for the progression of the reaction, with the optimal N2:H2 molar ratio being 2:1. This work highlights the necessity and significance of optimizing the reaction system, including (1) system configuration, (2) catalyst support material, and (3) operating parameter. Especially, it provides new insights into the design of catalysts in a plasma environment.