Selective electrocatalytic denitrification to N2 via dual single-atomic sites on double-shelled mesoporous carbon spheres

Abstract

Electrocatalytic denitrification (ECDN) offers a sustainable prospect by enabling efficient NO₃⁻ conversion to harmless N₂. However, the N₂-selective ECDN remains challenging due to the sluggish kinetics of N–N coupling during NO₃⁻ reduction. Here, we developed a novel electrocatalyst of dual single-atomic sites on double-shelled mesoporous carbon spheres (FeNC@MgNC-DMCS) using a continuous sequential modular assembly and pyrolysis approach. The outer Mg–N₄ shell creates medium basicity sites that function as the proton fence, which optimizes the spatial distribution of H∗ species and suppresses ∗N protonation pathways that would otherwise lead to ammonia formation. Concurrently, the inner Fe–N₄ shell promotes N–N coupling for N₂ production. 92.8% NO₃⁻ removal and 95.2% N₂ selectivity was achieved by the optimized FeNC@MgNC-DMCS catalyst. Furthermore, long-term flow cell testing demonstrated remarkable durability, highlighting the practical potential of FeNC@MgNC-DMCS for sustainable wastewater treatment applications. This work introduces a catalyst design paradigm that integrates a proton-repelling interface to decouple H∗ availability from N₂ formation pathways, thereby enabling the development of high-performance ECDN catalysts with balanced activity and selectivity for environmental remediation applications.