An in situ reconstructed CuOx–BTA heterointerface enables stable and selective nitrate electroreduction to ammonia

Abstract

The electrocatalytic nitrate reduction reaction (NitrRR) to ammonia offers a sustainable approach for wastewater treatment and value-added chemical synthesis. However, its practical application is hindered by sluggish kinetics and low selectivity, stemming from complex proton–electron transfer processes. Herein, we report an in situ electrochemical reconstruction strategy to construct a CuO_x–BTA heterojunction catalyst, where CuO_x species are controllably derived from a Cu-based metal–organic framework (Cu–BTA) precursor. The engineered interface induces strong interfacial charge transfer from CuO_x to BTA, promoting electron localization on Cu active sites and optimizing the adsorption energy of key intermediates. These structural and electronic features establish a dual-functional synergy: Cu⁰ sites catalyze the critical conversion of NO₃⁻ to NO₂⁻, while Cu⁺ sites facilitate the subsequent reduction of NO₂⁻ to NH₃. Meanwhile, the BTA ligand enhances NO₃⁻ activation and water dissociation, providing abundant *H intermediates for NH₃ formation. Benefiting from this cooperative mechanism, the catalyst achieves a remarkable NH₃ faradaic efficiency of 99.2% at −0.68 V vs. RHE and maintains stable performance for over 100 hours, significantly outperforming individual components (Cu–BTA, CuNPs and Cu₂O). This study demonstrates the potential of electrochemical reconstruction-driven interface engineering for the rational design of high-performance cascade NitrRR catalysts.