Reversible Decay of Oxygen Evolution Activity of Iridium Catalysts
Reversible Decay of Oxygen Evolution Activity of Iridium Catalysts
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DOI：
10.1149/2.0491914jes
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发表时间：
2019-10
影响因子：
3.9
通讯作者：
Robert Tang-Kong;C. Chidsey;P. McIntyre
中科院分区：
文献类型：
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作者：
Robert Tang-Kong;C. Chidsey;P. McIntyre
长期以来，铱一直被认为是最好的析氧催化剂之一，在活性和稳定性方面，在很宽的pH值范围内。尽管最初表现出高活性的析氧反应（OER），一个快速和可逆的活性衰减过程中观察到连续操作。探讨了活性恢复的电位依赖性，发现0.0 V vs NHE是恢复初始水氧化性能的有效电位。旋转盘电极上的铱薄膜被用来表明，这种OER活性衰减既不是由铱的渐进氧化，也不是由减少质量运输到/从电极表面。仔细检查活性衰减的时间依赖性，发现它可以通过多种电化学电池几何形状的at-1/4函数依赖性很好地描述。Tafel行为分析正常脉冲伏安法，表明，在10分钟的活性衰减后，催化剂表现出五倍的活性中心密度下降，而水的氧化机制没有改变。我们推测，这种衰变可能是由于能够形成Ir（V）= O物种的活性位点的损失，可能是通过桥接μ-氧化物的铱位点的逐步交联。
Iridium has long been recognized as one of the best oxygen evolution catalysts in terms of activity and stability over a wide range of pH. Despite exhibiting initially high activity for the oxygen evolution reaction (OER), a rapid and reversible activity decay is observed during continuous operation. The potential dependence of recovery of the activity is explored, and 0.0 V vs NHE is found to be an effective potential to recover the initial water oxidation performance. Iridium thin films on rotating disk electrodes are used to show that this OER activity decay is neither explained by progressive oxidation of the iridium nor by reduced mass transport to/from the electrode surface. Careful examination of the time dependence of the activity decay reveals that it is well described by at− 1/4 functional dependence across multiple electrochemical cell geometries. Tafel behavior is analyzed by normal pulse voltammetry, suggesting that, after 10 minutes of activity decay, the catalyst exhibits a five-fold decrease in active site density while the mechanism of water oxidation is not altered. We hypothesize that this decay may result from a loss of active sites capable of forming the Ir (V)= O species, possibly via progressive cross-linking of iridium sites by bridging mu-oxides.