Developing effective electrocatalysts for nitrate reduction to ammonia is paramount for ammonia synthesis while addressing the water pollutant issue. Identifying the active structure and its correlation with catalytic behavior during the reaction process is essential and challenging for the rational design of advanced electrocatalysts. Herein, starting from Cu₂O particles with controllable crystal facets, the electrochemically reconstituted Cu/Cu₂O was fabricated as a suitable catalytic system, and the relationship between the chemical state of copper and product selectivity in the nitrate reduction reaction was studied. At −0.9 V versus reversible hydrogen electrode, the oxide-derived Cu⁰ (OD-Cu) cube achieved a high ammonia Faradaic efficiency of 93.9% and productivity of up to 219.8 μmol h^–1 cm^–2, surpassing those of most Cu-based catalysts. In situ Raman analysis, well-designed pulsed electrolysis experiments, and theoretical calculations showed that ammonia was preferentially produced on OD-Cu at high reduction potentials and the presence of the Cu/Cu₂O interface favored nitrite formation at low reduction potentials. The high ammonia selectivity of the OD-Cu cube originated from the enhanced adsorption of nitrate and lower reaction barrier of the potential-determining step (*NH₃ → NH₃). This work presents an effective strategy to boost electrocatalysis and offers an insight into the real active phase and corresponding catalytic behavior of Cu-based electrocatalysts.

中文翻译：

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用于硝酸盐选择性还原氨的氧化物衍生铜电催化剂的电位诱导合成和结构鉴定

在解决水污染问题的同时，开发有效的硝酸盐还原成氨的电催化剂对于氨合成至关重要。在反应过程中识别活性结构及其与催化行为的相关性对于合理设计先进的电催化剂至关重要且具有挑战性。在此，以具有可控晶面的Cu ₂ O颗粒为出发点，制备了电化学重构的Cu/Cu _{2 O作为合适的催化体系，并研究了硝酸盐还原反应中铜的化学状态与产物选择性之间的关系。}在-0.9 V 相对于可逆氢电极，氧化物衍生的 Cu ⁰(OD-Cu) cube 实现了 93.9% 的高氨法拉第效率和高达 219.8 μmol h ^–1 cm ^–2的生产率，超过了大多数铜基催化剂。原位拉曼分析、精心设计的脉冲电解实验和理论计算表明，氨优先在高还原电位下在 OD-Cu 上生成，而 Cu/Cu 2 O 界面的存在有利于在低还原电位下形成亚_硝酸盐。OD-Cu立方体的高氨选择性源于硝酸盐的增强吸附和电位决定步骤的较低反应势垒（*NH ₃ → NH ₃). 这项工作提出了一种促进电催化的有效策略，并提供了对铜基电催化剂的真实活性相和相应催化行为的深入了解。