Bypassing Hydrogenation Pathway for Sustainable Nitrate Water Remediation via Direct N─N Coupling

ABSTRACT Catalytic nitrate (NO 3 − ) reduction (CNR) to dinitrogen (N 2 ) offers an efficient strategy for remediating nitrogen pollution but is constrained by preferred ammonia (NH 3 ) formation. This selectivity challenge arises because hydrogen atom (H*)‐mediated pathway inherently favors N─H coupling over the desired N─N coupling. Here, we report a formic acid (HCOOH)‐driven proton‐coupled electron transfer (PCET) pathway on a precisely engineered Sn 3 /Pd catalyst. The catalyst design features a synergistic bimetallic interface where Pd sites facilitate HCOOH activation while triangular Sn 3 ensembles selectively adsorb NO 3 − . This direct PCET from HCOOH to NO 3 − achieved a remarkable 96.5% NO 3 − removal and 97.4% N 2 selectivity at environmentally relevant concentrations (100 mg‐N/L). Operando mass spectrometry and density functional theory (DFT) calculations reveal that Sn 3 ensembles thermodynamically favored N─N coupling while also acting as a steric barrier that kinetically impedes H* migration to adsorbed N* intermediates, effectively suppressing NH 3 formation. Furthermore, by integrating the CNR process with electro‐synthesized HCOOH, we demonstrated a synergistic technology that slashed the carbon footprint of wastewater treatment by 43.3%, decreasing from 33.50 kg CO 2 ‐eq t −1 to 19.01 kg CO 2 ‐eq t −1 . Our work establishes atomic ensemble engineering as a powerful strategy to steer catalytic pathway through PCET, offering a viable solution for sustainable NO 3 − removal.