OH⁻/H₂O-reactant discrimination for the oxygen evolution reaction (OER) is a critical but not well resolved issue. This has led to unreasonable activity comparisons, misinterpreted OER mechanisms, and ununified models for theoretical calculations regardless of the thermodynamic/kinetic difference between OH⁻ and H₂O oxidation. Here, we discriminate between OH⁻ and H₂O oxidation by tuning the interfacial OH⁻ concentration. Combining OER kinetic analysis with in situ ¹⁶OH⁻/H₂¹⁸O isotopic labeling-based differential electrochemical mass spectrometry, we examine the respective electrochemical oxidation behaviors between OH⁻ and H₂O oxidation. We find that OH⁻ oxidation presents ∼550 mV lower onset potential relative to H₂O oxidation and that Tafel plotting gives slopes of ∼50 mV dec⁻¹ for OH⁻ oxidation, which is substantially lower than those of ∼200 mV dec⁻¹ for H₂O oxidation on a model CoOOH catalyst. This work calls for the discrimination of OH⁻/H₂O oxidation as the prerequisite for future OER activity evaluation and mechanism studies.

中文翻译：

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析氧反应中 OH− 和 H2O 氧化的区分


析氧反应 （OER） 的 OH⁻/H₂O 反应物区分是一个关键但尚未得到充分解决的问题。这导致了不合理的活性比较、对 OER 机制的误解以及不统一的理论计算模型，而不管 OH⁻ 和 H₂O 氧化之间的热力学/动力学差异如何。在这里，我们通过调整界面 OH⁻ 浓度来区分 OH⁻ 和 H₂O 氧化。将 OER 动力学分析与基于原位¹⁶OH⁻/H₂¹⁸O 同位素标记的差分电化学质谱相结合，我们研究了 OH⁻ 和 H₂O 氧化之间各自的电化学氧化行为。我们发现 OH⁻ 氧化相对于 H₂O 氧化的起始电位低 ∼550 mV，并且塔菲尔图给出 OH⁻ 氧化的斜率为 ∼50 mV ^dec-1，这大大低于模型 CoOOH 催化剂上 H₂O 氧化的 ∼200 mV ^dec-1。这项工作要求区分 OH⁻/H₂O 氧化作为未来 OER 活性评估和机制研究的先决条件。