In situ electrochemical reconstruction is important for transition metal oxides explored as electrocatalysts for electrochemical nitrate reduction reactions (ENRRs). Herein, we report substantial performance enhancement of ammonium generation on Co, Fe, Ni, Cu, Ti, and W oxide-based cathodes upon reconstruction. Among them, the performance of a freestanding ER-Co₃O_4-x/CF (Co₃O₄ grown on Co foil subjected to electrochemical reduction) cathode was superior to its unreconstructed counterpart and other cathodes; e.g., an ammonium yield of 0.46 mmol h^–1 cm^–2, an ammonium selectivity of 100%, and a Faradaic efficiency of 99.9% were attained at −1.3 V in a 1400 mg L^–1 NO₃^––N solution. The reconstruction behaviors were found to vary with the underlying substrate. The inert carbon cloth only acted as a supporting matrix for immobilizing Co₃O₄, without appreciable electronic interactions between them. A combination of physicochemical characterizations and theoretical modeling provided compelling evidence that the CF-promoted self-reconstruction of Co₃O₄ induced the evolution of metallic Co and the creation of oxygen vacancies, which promoted and optimized interfacial nitrate adsorption and water dissociation, thus boosting the ENRR performance. The ER-Co₃O_4-x/CF cathode performed well over wide ranges of pH and applied current and at high nitrate loadings, ensuring its high efficacy in treating high-strength real wastewater.

中文翻译：

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用于从高浓度硝酸盐废水中生成铵的金属氧化物阴极的原位重建：阐明底物在 Co3O4-x 性能中的作用

原位电化学重建对于探索作为电化学硝酸盐还原反应 (ENRR) 电催化剂的过渡金属氧化物非常重要。在此，我们报告了重建后 Co、Fe、Ni、Cu、Ti 和 W 氧化物基阴极上铵生成的显着性能增强。其中，独立式 ER-Co ₃ O _{4- x} /CF（在经过电化学还原的 Co 箔上生长的 Co ₃ O ₄）正极的性能优于其未重构的对应物和其他正极；例如，在 1400 mg L 的 -1.3 V 下，铵产率为 0.46 mmol h ^–1 cm ^{–2 ，铵选择性为 100%，法拉第效率为 99.9%–1} NO ₃ ^– –N 溶液。发现重建行为随底层基板而变化。_{惰性碳布仅作为固定Co 3} O ₄的支撑基质，它们之间没有明显的电子相互作用。_{物理化学表征和理论模型的结合提供了令人信服的证据，表明 CF 促进的 Co 3} O ₄自重构诱导金属 Co 的演化和氧空位的产生，从而促进和优化界面硝酸盐吸附和水离解，从而促进ENRR 性能。ER-Co ₃ O _{4- x}/CF 阴极在广泛的 pH 值和施加电流以及高硝酸盐负载下表现良好，确保其在处理高强度实际废水方面的高效性。