Rational Design of BN-Based Biphenylene Analogues as Single-Atom Catalysts for Electrochemical Nitrogen Reduction Reaction

The development of highly efficient and sustainable catalysts for ammonia synthesis is critical to addressing the energy-intensive nature and environmental impact of the conventional Haber–Bosch process. In this study, we explore boron (B)- and nitrogen (N)-based two-dimensional (2D) analogues of the recently synthesized biphenylene as promising materials for the electrochemical nitrogen reduction reaction (eNRR). Using density functional theory (DFT), we propose two novel 2D structures, bpw-BN and bp-BN, derived from the biphenylene carbon allotrope. The structural stability, electronic properties, and mechanical characteristics of these new materials are thoroughly analyzed. To enhance catalytic performance, we introduce divacancy defects in both bpw-BN and bp-BN, facilitating the anchoring of single transition metal (TM) atoms (V, Cr, and Mo). These TM-anchored systems exhibit remarkable electrochemical stability, evidenced by high binding energies and positive dissolution potentials, which prevent aggregation and dissolution under the reaction conditions. N 2 adsorption studies reveal that the catalysts effectively activate N 2 via σ-donation and π* back-donation, with strong binding to *N 2 and *N 2 H intermediates, suppressing the hydrogen evolution reaction (HER). Gibbs free energy analysis identifies the potential-determining steps for various reaction pathways, enabling the screening of six optimal catalysts out of 27 for a high NH 3 production efficiency. Additionally, by comparison with HER limiting potentials (making it 3 + 1 screening strategy), three NRR dominant electrocatalysts were finally identified. Among them, Cr 68-1 @bpw-BN exhibits the lowest overpotential of 0.09 V, establishing it as the best-performing catalyst. Our results demonstrate that the TM@bp-BN catalysts are not only structurally robust but also exhibit superior catalytic activity and selectivity for eNRR under ambient conditions. This investigation delivers a promising approach for the rational design of advanced single-atom catalysts, offering a pathway toward sustainable ammonia production.