Micropore–Metal Synergy in FAU Zeolite-Supported Ni Catalysts for Plasma-Assisted Ammonia Synthesis

Non-thermal plasma enables ammonia synthesis under mild conditions, but net performance is often limited by inefficient use of transient reactive species and plasma-driven NH 3 decomposition. Here we demonstrate that microporous confinement becomes decisively beneficial only when coupled to metal active sites. By benchmarking Ni catalysts supported on zeolites with distinct micropore architectures (BEA, MOR, FAU) against mesoporous and nonporous analogues in a dielectric barrier discharge (DBD) reactor, FAU emerges as the most effective microporous partner and delivers markedly improved activity and energy efficiency over mesoporous benchmarks. We elucidated the origin of this advantage using targeted controls (alkaline treatment/ion exchange), plasma electrical diagnostics (Q–V analysis/ignition behavior), and N 2 /H 2 /NH 3 adsorption/desorption probing under plasma. The results support a dual role of FAU micropores: enriching plasma-generated N/H species near Ni sites via confinement-enhanced residence time, and suppressing NH 3 loss through selective uptake into plasma-inaccessible micropores. MgO basic promotion further mitigates hydrogen over-coverage on Ni, yielding 7.55 mmol·h −1 ·g cat −1 and 1.65 g NH3 ·kWh −1 , competitive with reported Ni-based DBD plasma-assisted catalysts under comparable mild conditions. These findings establish micropore–metal synergy in zeolite-supported Ni catalysts as a guiding design principle for plasma-assisted ammonia synthesis. Graphical Micropore–metal synergy in zeolite-supported Ni catalysts promotes plasma-assisted ammonia synthesis by enriching plasma-derived N/H species and suppressing NH 3 decomposition. Additional MgO promotion relieves H over-coverage on Ni, further improving the NH 3 formation rate and energy efficiency.