Boosting Selective Ammonia Electrosynthesis from Nitrate Over Noble Metal Catalysts Via Surface Oxidation Engineering

ABSTRACT

Electrochemical nitrate reduction reaction to ammonia (NO ₃ RR) represents a sustainable pathway for closing the nitrogen cycle. However, the inherent activity‐selectivity dilemma and fierce competing hydrogen evolution reaction (HER) severely restrict the practical application of noble‐metal‐based catalysts. Here, we report a universal low‐temperature surface oxidation engineering strategy to reconstruct noble‐metal (Ru, Ir, Pd, Pt) electrocatalysts. The resulting modification achieves simultaneous enhancement of NO ₃ RR activity and efficient HER suppression, addressing a key challenge that is difficult to balance in conventional noble‐metal‐based catalysts. The optimized carbon‐supported core‐shell catalyst consisting of a Ru core and ultrathin RuO ₂ shell (Ru@RuO ₂ /C) enables excellent ammonia Faradaic efficiency of over 90.0% from 0.05 to −0.2 V vs. RHE, with a maximum Faradaic efficiency of 99.91% and a yield rate of 2.18 mg h ⁻¹ mg _cat ⁻¹ at 0 V vs. RHE. In situ spectroscopic analyses and theoretical calculations reveal that the Ru@RuO ₂ /C effectively optimizes the adsorption of ^* NO ₃ and suppresses the HER owing to interfacial charge transfer and electron density redistribution across the Ru and RuO ₂ interface. Applying the Ru@RuO ₂ /C as the cathode catalyst, the assembled Zinc−nitrate battery exhibits a peak power density of 60.5 mW cm ⁻² and a specific capacity of 829 mAh g ⁻¹ at 100 mA cm ⁻² .