Co-adsorbate-mediated nitrogen electroreduction on two-dimensional W@BC4N single-atom catalyst: Insight from first-principles

Abstract

Co-adsorbed intermediates ubiquitous on catalyst surface play an important role in mediating the reaction pathway. Herein, we systematically explore the co-adsorbate (*N2 and *H)-mediated nitrogen electroreduction reaction (NRR) on graphene-like W@BC4N single-atom catalyst (SAC) using density-functional theory (DFT) calculation and ab-initio molecular dynamics (AIMD) simulation. The results reveal that the multiple NRR pathways dependent on adsorption mode of *N2 can cross over with one another. The proton-coupled electron transfer (PCET) in NRR is likely to couple with the intermolecular hydrogen-transfer. With three *N2 and two *H as spectators, NRR can proceed via a mixed consecutive-enzymatic mechanism, where the 6th PCET, *NH2 + (H+ + e-) → *NH3, is the potential-limiting step with UL = -0.72 V, larger than those (UL = -0.47 V, UL = -0.52 V and UL = -0.67 V) absence of the co-adsorbed *N2. Nonetheless, the co-adsorbed *N2 can facilitate the desorption of *NH3, beneficial to catalytic cycling. Given the steric hindrance of the co-adsorbed NHx intermediates, hydrazine (N2H4) is most likely to be produced during NRR. With W single-atom site working synergistically with the adjacent B site, W@BC4N has demonstrated the high promise for driving NRR.