Adsorption Energies of Various Intermediates of Ammonia Synthesis on Pure Metal Catalysts

The production of ammonia through the Haber-Bosch process requires extreme reaction conditions. Nitrogen reduction reaction (NRR) can also be performed using electrocatalytic, photocatalytic, and enzymatic methods under ambient conditions and is being considered as an alternative for ammonia synthesis. Transition metals have been used significantly as catalysts for electrochemical synthesis of ammonia. The NRR can follow two types of mechanisms: dissociative and associative. The associative mechanism can follow two different pathways, alternating and distal. In this work, density functional theory is used to calculate the adsorption energies of different NRR intermediates on various transition metal surfaces and is used as an indicator to predict the probable mechanism of the reaction. The favorability of the reaction to follow the dissociative or associative mechanism is determined by comparing the adsorption energy values of 2*N and *NNH. The alternating or distal pathway of the associative mechanism is decided from the stability of the intermediates *NHNH and *NNH2.