Clear structure–performance relationships are helpful for the design of efficient catalysts and the understanding of reaction mechanisms. The electrocatalytic nitrate reduction reaction (NO₃RR) offers a sustainable route to ammonia (NH₃) synthesis and nitrate mitigation. However, it suffers from poor nitrate adsorption, low NH₃ selectivity and sluggish reaction kinetics. Herein, N-doped carbon nanosheets supported Fe₃C nanoflakes featuring large surface areas (860.024 m² g⁻¹) were prepared. Their NO₃RR performances showed volcano-like relationships with the Fe³⁺/Fe²⁺ ratios and d-band centers. At −0.5 V, the NH₃ yield, faradaic efficiency, selectivity and current density reached 1.19 mmol h⁻¹ mg⁻¹, 96.7%, 79.0% and 85.6 mA cm⁻², respectively, exceeding most reported results. Such exceptional performances mainly originated from the optimized electronic structures that boosted nitrate adsorption and reaction kinetics (Tafel slope: 56.7 mV dec⁻¹). Mechanistic investigations revealed a NO₃⁻ → NO₂⁻ → NH₃ reaction pathway with the chemical process following the fast electron transfer process as the rate-determining step.

中文翻译：

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通过 Fe3C 纳米薄片的电子结构工程促进硝酸盐电还原产生 NH3

清晰的结构-性能关系有助于设计高效催化剂和理解反应机理。电催化硝酸盐还原反应 (NO ₃ RR) 提供了合成氨 (NH ₃ ) 和减少硝酸盐的可持续途径。然而，它存在硝酸盐吸附差、NH ₃选择性低和反应动力学缓慢的问题。在此，制备了具有大表面积（860.024 m ² g ^-1）的N掺杂碳纳米片负载的Fe ₃ C纳米薄片。它们的 NO ₃ RR 性能与 Fe ³⁺ /Fe ²⁺表现出类似火山的关系比率和 d 波段中心。在-0.5 V 时，NH ₃产率、法拉第效率、选择性和电流密度分别达到1.19 mmol h ^-1 mg ^-1、96.7%、79.0% 和85.6 mA cm ^-2，超过了大多数报道的结果。这种卓越的性能主要源于优化的电子结构，可提高硝酸盐吸附和反应动力学（Tafel 斜率：56.7 mV dec ^-1）。机理研究揭示了 NO ₃ ^- → NO ₂ ^- → NH ₃反应途径，其中快速电子转移过程之后的化学过程作为速率决定步骤。