Defect‐Rich AuCu/CuS Nanowires Heterojunction for Light‐Enhanced Sulfur Ion Electrooxidation Coupled Nitrite Electroreduction

In this work, defect-rich AuCu/CuS nanowires (NWs) heterojunction with abundant amorphous active sites and distinct electronic structure are successfully achieved by post-sulfurization strategy and exhibited excellent electroactivity for nitrite electroreduction reaction (NO₂ERR). Meanwhile, sulfur ion electrooxidation reaction (SEOR) is used to replace OER, and NO₂ERR-SEOR coupling system is formed to achieve low-voltage NH₃ production. Moreover, due to the localized surface plasmon resonance (LSPR) property of Au, AuCu/CuS NWs show an obviously plasmon-promoted activity for both NO₂ERR and SEOR. An efficient NO₂ERR-SEOR electrolyzer displays a lower electrolysis voltage (0.74 V) under light irradiation conditions, shedding light on a novel approach to design next-generation NH₃ electrocatalysts.

Abstract

The nitrite electroreduction reaction (NO₂ERR) offers a promising pathway for ammonia (NH₃) synthesis and the remediation of nitrite pollutants. Copper (Cu)-based nanomaterials have demonstrated significant potential as NO₂ERR catalysts, but their catalytic activity and durability are hindered by limitations in the hydrogenation process. In this work, alloying and post-sulfurization strategies are employed to synthesize AuCu/CuS nanowires (NWs), which feature abundant amorphous active sites and distinct electronic structures. AuCu/CuS NWs exhibit high electroactivity for both NO₂ERR (Faradaic efficiency: 95.26%; NH₃ yield: 2.54 mg h⁻¹ g_cat ⁻¹) and sulfur ion electrooxidation reaction (SEOR, oxidation potential: −0.05 V at 10 mA cm⁻²). In situ characterization and theoretical calculations explain that amorphous CuS can modify the electronic property of AuCu alloy, thereby optimizing the adsorption of active hydrogen and nitrogen-containing intermediates. Using AuCu/CuS NWs as a bifunctional electrocatalyst, the assembled NO₂ERR||SEOR two-electrode system only requires the electrolysis voltage of 0.77 V to obtain the current density of 10 mA cm⁻², accompanied by the co-production of sulfur and NH₃. Under light irradiation conditions, the electrolysis voltage of the NO₂ERR||SEOR two-electrode system is further reduced under light irradiation conditions. This study offers a novel approach for the co-generation of value-added products through NO₂ERR coupled with SEOR.