The Journey toward Low Temperature, Low Pressure Catalytic Nitrogen Fixation

Ammonia and its derived products are vital to modern societies. Artificial nitrogen fixation to ammonia via the Haber-Bosch process has been employed industrially for over 100 years. However, the Haber-Bosch process is energy intensive and not sustainable in its current form as it uses hydrogen sourced from steam methane reforming to reduce N-2. The roadmap to sustainable NH3 production demands the discovery of novel approaches for nitrogen fixation under near ambient conditions that preferably use water as the reducing agent. Over the last decade, great efforts have been made to develop catalysts capable of N-2 fixation under mild reaction conditions, using strategies such as low temperature thermal catalysis, nonthermal plasma catalysis, enzymatic catalysis, photocatalysis, and electrocatalysis to generate ammonia and other valuable nitrogen-containing chemicals. In parallel with catalytic performance studies, researchers have also placed emphasis on the mechanistic understanding of natural and artificial nitrogen fixation catalysts. In this work, the various routes now being explored for nitrogen fixation are summarized. The different dinitrogen activation and hydrogenation pathways are described, whilst describing key advances made to date on the journey toward near ambient ammonia synthesis. Key obstacles that need to be overcome to attract industry interest are also discussed.