Theoretical insights into the electroreduction mechanism of N₂ to NH₃ from an improved Au(111)/H₂O interface model

Abstract

The associative alternating and distal mechanisms may be able to parallelly occur. The initial N2 reduction into N2H species is rate determining step, which may be able to be regarded as the origin of high overpotential.

Theoretical evaluation of the effect of bimetallic Au-based alloy catalysts on initial N2 electroreduction pathways

“…0.24 eV vs. 1.75 eV). 29 The comparison of activation barriers between HER and initial N 2 electroreduction well explains why Au electrocatalytic activity is unsatisfactory despite the relatively higher faradaic efficiency that can be experimentally achieved compared to other transition metals. 21,22,55 In this work, the barriers of HER are evaluated by MEP analysis at AuM(111)/H 2 O interfaces (M = Ni, Pd, Pt, Ru, and Ta) with different atomic ratios and compared with that of initial N 2 electroreduction into N 2 H species to quantify the challenge in designing high efficient Au-based alloy electrocatalysts.…”

“…† Our most recent and previous theoretical studies have shown that the initial N 2 electroreduction into N 2 H intermediate is a rate-determination step during NH 3 production on Au and other late transition metals. 29,42,43 An extremely high activation barrier of ca. 1.75 eV for initial N 2 electroreduction into the N 2 H species was obtained on a pure Au(111) surface in our most recent study, 29 which may be able to be looked upon as the origin of unsatisfied faradaic efficiency and NH 3 yield during N 2 electroreduction on clean Au electrodes.…”

“…29,42,43 An extremely high activation barrier of ca. 1.75 eV for initial N 2 electroreduction into the N 2 H species was obtained on a pure Au(111) surface in our most recent study, 29 which may be able to be looked upon as the origin of unsatisfied faradaic efficiency and NH 3 yield during N 2 electroreduction on clean Au electrodes. Thereinto, weakly bonded and non-activated N 2 molecules with the low adsorption energy of ca.…”

“…28 However, the reported activity of Au electrodes is also unsatisfactory and N 2 electroreduction is still plagued by physically adsorbed N 2 molecules on a clean Au surface. 29 Most recently, great efforts have been made to further improve the electrocatalytic activity of metal catalysts for N 2 reduction, such as the design and preparation of bimetallic alloy electrocatalysts. [30][31][32][33][34][35][36][37] The electronic structure of metals and adsorption property of N 2 molecules on the surface can be changed by alloying two metals.…”

Strategies in cell design and operation for the electrosynthesis of ammonia: status and prospects

“…From a theoretical perspective, it remains debatable whether the N 2 adsorption and activation occur more favourably at the solid-liquid interface (i.e., dissolved N 2 as reactant) or at the three phase interface (i.e., gaseous N 2 as reactant). Ou et al 50 modelled a gold (111) surface flooded with H 2 O and found the electronic interaction between dissolved N 2 and H 2 O is critical in reducing the activation energy of the ratedetermining step (the first hydrogenation step to produce N 2 H). By contrast, when exposing Au only to N 2 gas without the involvement of H 2 O, destabilizing the NRN bond at the Au-N 2 interface suffers a higher kinetic barrier because of an insufficient valence electron gain from H 2 O.…”