| Abstract |
Ammonia as a green energy source has attracted a lot of attention in recent years. Despite its industrial intensity, the Haber-Bosch process remains a primary ammonia source, emitting significant CO2 (approximate to 2.9 tons per ton of ammonia). Future ammonia synthesis methods aim to surpass the Haber-Bosch process by operating under milder conditions. These methods encompass chemical looping, thermal catalysis, electrochemical catalysis, photocatalysis, and plasma catalysis, albeit with inherent limitations. Although thermal catalysis has reduced conditions to approximate to 5 MPa, innovative catalysts are still scarce. Electrochemical catalysis produces hydrogen via water electrolysis but encounters challenges in Faraday efficiency and ammonia yield. Photocatalytic synthesis, while energy-efficient, suffers from sluggish reaction rates. Plasma synthesis, while achieving low temperatures and pressures, faces difficulties in ammonia yield amidst competitive reactions. Chemical looping synthesis, enabling independent nitrogen fixation and hydrogenation, lacks efficient nitrogen transport catalysts. Effective catalysts are a common requirement across these methods. This review explores recent advancements, elucidating reaction mechanisms, nitrogen activation, and catalyst performance, while discussing the strengths, weaknesses, and future prospects of ammonia synthesis technologies to foster further innovation in the field. This paper reviews the current status of research on several major ammonia synthesis technologies. The advantages and disadvantages of thermal catalytic ammonia synthesis, electrochemical ammonia synthesis, photocatalytic ammonia synthesis, and plasma ammonia synthesis are compared. The future development direction of green ammonia synthesis technology is proposed. image |
