Copper oxide nanowires with varying oxidation states are prepared and their activity for water oxidation is studied. The nanowires with a CuO phase are found to be the most active, and their degree of crystallinity is important in achieving efficient water oxidation. For the crystalline CuO nanowires in a weakly basic Na₂CO₃ electrolyte, a Tafel slope of 41 mV/decade, an overpotential of approximately 500 mV at ~ 10 mA/cm² (without compensation for the solution resistance), and a faradaic efficiency of nearly 100% are obtained. This electrode maintains a stable current for over 15 h. The low overpotential of 500 mV at 10 mA/cm², small Tafel slope, long-term stability, and low cost make CuO one of the most promising catalysts for water oxidation. Moreover, the evolution of the CuO nanowire morphology over time is studied by electron microscopy, revealing that the diffusion of Cu ions from the interior of the nanowires to their surface causes the aggregation of individual nanowires over time. However, despite this aggregation, the current density remains nearly constant, because the total electrochemically active surface area of CuO does not change.

中文翻译：

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洞察铜基纳米线用于电催化氧逸出的效率和稳定性

制备了具有不同氧化态的氧化铜纳米线，并研究了其对水氧化的活性。发现具有CuO相的纳米线是最活跃的，其结晶度对于实现有效的水氧化非常重要。对于弱碱性Na ₂ CO ₃电解质中的结晶CuO纳米线，Tafel斜率为41 mV /十倍，在〜10 mA / cm ²时约500 mV的过电势（不补偿溶液电阻），以及法拉第效率获得了将近100％。该电极保持稳定的电流超过15小时。10 mA / cm ^2时500 mV的低过电势，Tafel斜率小，长期稳定性和低成本使CuO成为水氧化最有前景的催化剂之一。此外，通过电子显微镜研究了CuO纳米线形态随时间的演变，揭示了Cu离子从纳米线内部到其表面的扩散会导致各个纳米线随时间聚集。然而，尽管有这种聚集，由于CuO的总电化学活性表面积不变，因此电流密度几乎保持恒定。