Density functional theory is used to evaluate electrocatalytic synthesis of ammonia at ambient conditions on the surface of transition metal sulphides as cathode catalyst. The proposed catalysts, inspired by the nature and following the nitrogenase mechanism, can be a promising alternative for CO₂-free, decentralised, and sustainable production of fertilisers. Several different surfaces of transition metal sulphides were modelled, YS, ScS, and ZrS in the rocksalt structure with the (1 0 0) facet; TiS, VS, CrS, NbS, NiS, and FeS in NiAs-type structure with the (1 1 1) facet; and MnS₂, CoS₂, IrS₂, CuS₂, OsS₂, FeS₂, RuS₂, RhS₂, and NiS₂ in pyrite structure for both the (1 0 0) and (1 1 1) orientations, as the most stable structures. Nitrogen reduction reaction (NRR) was investigated via both the associative and dissociative mechanisms and the overpotential required for electrochemical ammonia formation on these surfaces were predicted. With the use of adsorption energies of intermediates we constructed the scaling relations as well as the volcano plots with the *NNH as the descriptor. The outcome of this comprehensive modelling was that RuS₂ could be the most active sulphide for catalysing NRR at potentials around −0.3 V through the associative mechanism along with few more promising sulphides close to the top of the volcano plot ¹.

Reference:

1. Abghoui, Y., Sigtryggsson, S. B. & Skúlason, E. Biomimetic Nitrogen Fixation Catalyzed by Transition Metal Sulfide Surfaces in an Electrolytic Cell. ChemSusChem 12, (2019).