Graphyne supported Co13, Fe13 and Ni13 nano-cluster as efficient electrocatalysts for nitrogen reduction reaction: A first principles study.

A systematic first principles study is carried out to probe into the activity of graphyne supported Co 13 , Fe 13 and Ni 13 nano-clusters (NCs) towards the reduction of nitrogen (N 2) into ammonia (NH 3). Graphyne is found to highly stabilize the metal nano-clusters on its large pores through an exothermic chemisorption process. Adsorption of N 2 on the graphyne supported NCs are detected to be highly exothermic in both end-on and side-on mode configurations. N 2 becomes more activated via a higher amount of N-N bond stretching when adsorbed in side-on configuration. The activation of the N-N bond is shown to be directly proportional to the amount of charge transfer to the adsorbed N 2 molecule. Thorough analysis of the nitrogen reduction reaction (NRR) on each graphyne supported metal NC reveals that NRR starting from side-on mode N 2 adsorbed configuration prefers the enzymatic pathway though other pathways are possible at the cost of relatively higher overpotential. Only the distal pathway is energetically favoured following the end-on mode N 2 adsorbed configuration. Graphyne supported Co 13 , Fe 13 and Ni 13 NCs are shown to carry out NRR with substantially low overpotential values of 0.24 V, 0.28 V and 0.37 V respectively. The active sites located far from the graphyne substrate are found to be more selective towards NRR with low overpotential than hydrogen evolution reaction. The NCs maintain their structural stability on the graphyne surface throughout the whole reaction process via different pathways showing that graphyne is a potentially very promising substrate material to stabilize the NC electrocatalysts and to improve their electrocatalytic activities towards NRR. [Display omitted] • NRR is studied theoretically for graphyne supported Co 13 , Fe 13 and Ni 13 nano-clusters. • The interaction of the nano-clusters with the graphyne substrate is investigated. • Electronic properties of the adsorbed nano-clusters and N 2 molecules in explored. • The selectivity of the chosen electrocatalyst systems towards NRR is established. [ABSTRACT FROM AUTHOR]