Design principles of biphenylene-supported dual-atom catalysts for efficient and selective nitrate reduction to ammonia

Abstract

The electrochemical nitrate reduction reaction (NO₃RR) offers a sustainable approach for converting nitrate pollutants into valuable ammonia under ambient conditions. Herein, we employ density functional theory (DFT) to systematically investigate the catalytic potential of homonuclear transition metal dual-atom catalysts (DACs) anchored on biphenylene (TM₂@BPN) for NO₃RR. Among 28 candidates, five DACs: Mo₂@BPN, Ru₂@BPN, Rh₂@BPN, Os₂@BPN, and Ir₂@BPN, exhibit low limiting potentials (−0.40 to −0.16 V) and exceptional ammonia selectivity. Rh₂@BPN, in particular, achieves a theoretical faradaic efficiency of 100%, effectively suppressing competing hydrogen evolution. Electronic analyses reveal that dual-site π-donation/π*-back-donation interactions, d-band center tuning, and charge redistribution collectively enhance NO₃⁻ activation compared to single-atom analogues. Importantly, descriptor-based volcano plots (ΔG_*NO3, ε_d, and ψ) establish generalizable design rules that correlate electronic structure with catalytic trends, enabling predictive DAC screening beyond exhaustive pathway calculations. Ab initio molecular dynamics simulations further confirm the thermal stability of the most active DACs. This work introduces biphenylene as a robust support for stabilizing DACs, establishes structure–property–performance correlations, and provides transferable mechanistic and descriptor-based insights for the rational design of next-generation catalysts for selective multi-electron electrochemical transformations such as nitrate-to-ammonia conversion.