Electroreduction reaction of nitrate (NO3RR) to ammonia (NH3) using reproducible energy is an effective alternative strategy to energy-intensive Haber-Bosch process and potentially energy storage. However, the reaction needs coupling of multiple electrons and protons, considering it a grand challenge to NH3 yield and selectivity affected by slow electron transfer kinetic processes. Herein, we investigate the electrode kinetics process by Tafel plots on Fe2O3 nanorods array electrocatalysts, confirming that the process of the first electron transfer is involved in the rate-determining step (RDS) for NO3RR. The reaction rate constant (k) of the first electron transfer (NO3– + e-→*NO3) indicates that Fe2O3 electrocatalyst treated at 450 ℃ has a faster electron transfer kinetic and thus exhibits a higher NH3 yield. Furthermore, operando EIS and in situ Raman spectroscopic characterizations demonstrate that electron gaining and losing process of Fe promotes the transfer of the first electron to NO3–, thus substantially accelerating the kinetic process of the RDS. These results provide key insight into the metal oxide-based electrocatalysts kinetic processes on the performance of NO3RR.

中文翻译：

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了解 Fe2O3 纳米棒阵列上电化学硝酸盐还原成氨的第一电子转移动力学过程


使用可再生能源进行硝酸盐 (NO3RR) 电还原反应生成氨 (NH3) 是能源密集型 Haber-Bosch 工艺和潜在能源存储的有效替代策略。然而，该反应需要多个电子和质子的耦合，考虑到缓慢的电子转移动力学过程对NH3产率和选择性的巨大挑战。在此，我们通过 Fe2O3 纳米棒阵列电催化剂上的 Tafel 图研究了电极动力学过程，证实第一次电子转移过程涉及 NO3RR 的速率决定步骤 (RDS)。第一次电子转移（NO3– + e-→*NO3）的反应速率常数（k）表明，在450 ℃处理的Fe2O3电催化剂具有更快的电子转移动力学，因此表现出更高的NH3产率。此外，原位电化学阻抗谱和原位拉曼光谱表征表明，Fe 的电子得失过程促进了第一个电子向 NO3- 的转移，从而大大加速了 RDS 的动力学过程。这些结果为了解金属氧化物基电催化剂动力学过程对 NO3RR 性能的影响提供了关键见解。