Sulfurization-induced in situ surface reconstruction of NiCu-LDH anodes synergized with Cu/NF cathodes for efficient electrocatalytic ammonia oxidation

Sulfurization-induced in situ surface reconstruction generates a Ni³⁺-rich NiOOH active phase for enhanced AOR activity. • Ni–Cu interaction optimizes interfacial electron transfer and promotes ammonia oxidation kinetics. • Cu/NF cathode promotes NO₃⁻/NO₂⁻ intermediate reduction and improves N₂ selectivity. • Anode–cathode synergistic catalysis integrates active phase reconstruction with intermediate regulation. • The integrated electrocatalytic system achieves > 98% NH₄⁺-N removal with high N₂ selectivity under mild conditions. Electrocatalytic ammonia oxidation (AOR) is a promising strategy for efficient ammonia removal and recovery; however, its practical application remains limited by sluggish reaction kinetics and low N₂ selectivity, while the structure–activity relationship between catalyst surface reconstruction and catalytic performance remains poorly understood. Herein, a sulfurization-modified NiCu layered double hydroxide (S-NiCu-LDH/NF) anode coupled with a Cu/NF cathode was rationally constructed to establish an anode–cathode synergistic electrocatalytic system for efficient NH₄⁺-N oxidation and selective nitrogen conversion. The optimized system achieved over 98% NH₄⁺-N removal within 90 min with an N₂ selectivity exceeding 82%. Electrochemical analyses reveal that sulfurization improves interfacial charge-transfer kinetics, while the Cu/NF cathode further facilitates electron transport through reduced charge-transfer resistance. XPS and Raman analyses suggest that sulfurization induces in situ surface reconstruction during electrolysis, accompanied by the formation of a Ni³ ⁺-rich NiOOH active phase. The reconstructed active phase is proposed to facilitate NH₃ activation and the adsorption and conversion of key reaction intermediates, thereby promoting multi-electron transfer during AOR. Meanwhile, the Cu/NF cathode promotes the electrochemical conversion of NO₂⁻ and NO₃⁻ intermediates, suppressing their accumulation and consequently improving N₂ selectivity through an anode–cathode synergistic process. Download: Download high-res image (232KB) Download: Download full-size image