Ni-Modified ZIF-67 for Efficient Plasma Catalytic Ammonia Synthesis

Developing alternatives to the energy-intensive Haber–Bosch (H–B) process for ammonia synthesis is imperative yet challenging. Herein, Ni-modified zeolitic imidazolate framework (ZIF) Ni@ZIF-67 nanocrystals were synthesized and applied in a dielectric barrier discharge reactor for plasma-assisted ammonia synthesis under ambient pressure. Introducing ZIF-67 into the plasma enhanced the ammonia synthesis rate by an order of magnitude, evidencing strong plasma–catalyst synergism. The superior performance was attributed to the unique microstructure featuring a high specific surface area and abundant porosity, which improved gas adsorption and intensified microdischarge within the plasma. Further incorporation of Ni into ZIF-67 (Ni@ZIF-67) resulted in a maximum ammonia synthesis rate of 289.45 μmol g–1 min–1 and an energy yield of 1.83 g kWh–1─a 32.0% improvement over ZIF-67─while maintaining structural stability over repeated cycles. Moreover, the confinement of NH3 within sub-Debye-length micropores suppressed plasma-induced decomposition. The addition of Ni further significantly boosted both the hydrogen/ammonia adsorption capability and discharge efficiency, which promoted ammonia formation, especially in a H2-rich atmosphere. These findings underscored the potential of Ni@ZIF-67 as a promising catalyst for plasma-assisted ammonia synthesis, providing a viable alternative to the conventional H–B process.