Active and selective nitrogen electroreduction is challenged by the need to activate the inert N-N triple bond and the competition with hydrogen evolution. Density functional theory has been used to argue that metal surfaces will inherently be non-selective and offer large overpotentials, due to scaling relationships that correlate all intermediate binding energies with a metal’s N adsorption energy [1-2]. In this talk, we will apply DFT to investigate the elementary kinetics of N₂ reduction on metal and metal-oxide surfaces. We will consider elementary kinetics across late transition metal surfaces to examine how the inclusion of kinetic consideration alters the trade-offs between the ability to activate N₂ and to reduce eventual NH_x species to ammonia. We then consider how electrolyte composition, including proton-transfer co-catalysts, alter the kinetics of reduction of surface bound intermediates on metal surfaces. We apply ab initio thermodynamics to determine the stability of oxide surfaces under N₂ reductions, then examine the elementary steps on the (partial reduced) oxide surfaces. We will present possible mechanistic avenues to using metal oxides and electrolyte/surface additives to alter the activity and selectivity of N₂ reduction electrocatalysts.

[1] Skulason et al. Physical Chemistry Chemical Physics, 2012, 14, 1235.

[2] Montoya et al. ChemSusChem 2015, 8, 2180-2186.