Ammonia is a critical chemical that sustains the global food chain by feeding approximately 40% of world’s population. Ammonia can also be utilized as a clean fuel or energy carrier to power efficient energy conversion devices. However, ammonia production based on Haber-Bosch process is increasingly challenged by scalability and energy intensity (consuming almost 2% of the world’s energy). Ideally, feasible ammonia synthesis processes enabling intermittent operations at milder conditions and smaller scale, as well as the integration with renewable energy sources, will bring the technological breakthrough in order to better suit current societal needs.

In this talk, theoretical density functional theory (DFT) will be used to evaluate a class of novel alternative materials for N₂ activation, ammonia formation and decomposition. Specifically, our recent work on transition metal or alloy-based nitrides (TMNs) will be discussed to show that the knowledge of molecular mechanism from theory is necessary and can lead to the formulation of guidelines to help identify appropriate materials and their optimizations. TMNs have been successfully demonstrated in stepwise, atmospheric ammonia synthesis in a nitridation cycle. Recent studies have also suggested that TMNs are also promising materials to catalyze N₂, via electroreduction, to ammonia under ambient conditions. By following a Mars-van Krevelan mechanism, we identified that the nitride formation thermodynamics and nitrogen species diffusion kinetics under relevant process condition are both the key and will invoke the consideration of both aspects simultaneously in the nitridation-reduction cycle. To improve the TMN performance, the simple strategy to modify the electronic structures of TMN by alloying with other transition metals, targeting both bond formation and nitrogen transport within TMN, will be presented. Derived from our computational findings, bifunctional materials that are capable of efficient N₂ activation and ammonia synthesis in synergy may hold the ultimate solution. Potential candidate materials that can be deployed for electrochemical or thermal ammonia production will be presented.