Asymmetrically Cu–O–Cu bridged dual-atom sites on bio-functionalized oxides for molecular nitrate upcycling

The electrochemical nitrate reduction reaction (NO 3 RR) is a promising strategy for decentralized ammonia (NH 3 ) production and environmental remediation under ambient conditions. However, achieving complete eight-electron/nine-proton (8e - /9H + ) conversion of NO 3 − to NH 3 with high selectivity and efficiency remains challenging owing to sluggish NO 3 − activation and competing N–N coupling side reactions such as N 2 , N 2 O, and NO gas evolution. Herein, we report a rationally designed Cu dual-atom (DA) catalyst composed of asymmetrically coordinated Cu atomic pairs anchored on an L-tryptophan-functionalized Fe 3 O 4 /α-Fe 2 O 3 heterostructure (Cu 2 /try-FeO X ), synthesized via a CO 2 laser irradiation method involving multi-step continuous-wave exposure for interface engineering. The hybrid Cu 2 /try-FeO X support provides abundant N and O coordination sites and enhanced electron mobility, enabling spatially separated Cu atom by asymmetrically coordinated Cu–N/O dual sites exhibit synergistic electronic interactions, forming robust DA configurations. In situ and ex situ spectroelectrochemical analyses, supported by theoretical calculations, confirm a *NO 3 → *NO 2 → *NO → *NHO → *NH 2 O → *NH 3 → NH 3 reaction pathway. At the optimal potential, the total Faradaic efficiency toward NH 3 and NO 2 ‒ approaches ∼95%, indicating effective suppression of competing H 2 , N 2 , and N 2 O formation and confirming a highly selective 8e ‒ /9H + NO 3 RR mechanism. Notably, NO 3 RR tests using Cu 2 /try-FeO X achieve a high NH 3 yield rate of 0.29 mmol h −1 cm −2 and a maximum Faradaic efficiency of 88.5% at −0.2 V vs. RHE. Furthermore, when integrated into a Zn–NO 3 − battery, the catalyst enables self-powered NO 3 − to NH 3 conversion with stable operation over 100 h. This study presents a rational approach that integrates DA site engineering catalyst design with bio-functional support design to regulate intermediate adsorption and electron transfer, thereby enhancing the activity and selectivity for self-powered molecular NO 3 − upcycling technologies.