Interfacial *NO Activation over Ultrafine MoC/Fe <sub>2</sub> O <sub>3</sub> Heterojunctions for Efficient Nitrate-to-Ammonia Electrosynthesis
Xiu Zhong, Zhenxiao Wang, Yingjie He, Mengting Liu, Mengting Liu, Fu Yang, Mingkai Xu, Hongmei Li, Liying Cao, Chao Yu, Yangping Zhang, Yanyun Wang, Haiying Wang, Yinlong Zhu, Weidong Shi, Min Liu, Min Liu
Abstract
The electrocatalytic nitrate reduction reaction (NO 3 RR) is often hindered by sluggish kinetics, primarily due to the challenging adsorption and activation of the key intermediate *NO, widely recognized as the rate-determining step. Rational engineering of active sites to modulate *NO binding and facilitate its hydrogenation is therefore essential yet remains a great challenge. Here, we report the design of topologically confined ultrafine MoC/Fe 2 O 3 heterojunctions embedded within interconnected porous carbon nanofibers (Mo 1 Fe 1.5 /CNF) via interfacial confinement engineering. This architecture yields a high density of localized relay catalytic sites characterized by Mo(IV)–O-Fe linkages. The resulting heterojunctions exhibit abundant oxygen vacancies and an enriched Mo(IV) population, enabling synergistic nitrate adsorption and *NO activation through interfacial charge redistribution and delocalization. The optimized Mo 1 Fe 1.5 /CNF catalyst achieves an excellent NH 3 yield of 38.49 mg h –1 mg cat –1 and a Faradaic efficiency of 99.4% at −1.2 V vs RHE, with stable performance over 10 operational cycles and 50 h of continuous electrolysis. Near-ambient pressure X-ray photoelectron spectroscopy, in situ Fourier transform infrared spectroscopy, and density functional theory calculations collectively showcase that *NO preferentially adsorbs on Mo(IV) sites adjacent to oxygen-vacancy-rich Fe 2 O 3, with the interfacial Mo–O–Fe motifs obviously lowering the hydrogenation energy barrier of *NO (∼0.32 eV).