AI 中文总结
本研究通过多电极实验结合光谱分析，证实微气泡中H₂O₂形成先于羟基自由基，反应活性位点为固-水界面，可基于电极预测微气泡是否产生CL，并质疑气-水界面自发形成羟基自由基的观点。
AI 中文摘要
针对近期研究提出的一种替代性解释——该研究将钢或铜电极在鲁米诺水溶液中（电压范围2-30 V）上电生成微气泡产生的持续化学发光（CL）和电化学发光（ECL）归因于气-水界面处羟基自由基的自发形成，本文对此进行了探讨。我们对钢、铜、铝、铂等多种电极开展实验，发现所有电极均可电生成微气泡，但仅钢和铜会产生CL，铝和铂则不会。这些观测结果表明，微气泡的气-水界面并非羟基自由基的生成位点（否则所有电极都会观测到CL）。对实验中H₂O₂的补充定量分析显示，其电极依赖性为：铝>铜>钢>铂。这表明，H₂O₂的形成取决于电极类型，且在某些情况下（即观测到CL/ECL时）会出现羟基自由基。通过NMR和EPR光谱实验，我们发现：（i）仅当水中存在O₂时才会形成H₂O₂；（ii）钢和铜通过H₂O₂的单电子还原生成羟基自由基，铝无法促进H₂O₂的单电子还原以产生羟基自由基，而铂则优先促进H₂O₂歧化为H₂O和O₂。事实上，我们证实即使没有微气泡，也可在特定的金属-水界面观测到H₂O₂和羟基自由基，这进一步确认了固体表面才是反应活性位点。因此，本研究可基于电极类型预测电生成微气泡是否会在鲁米诺溶液中产生CL，并对气-水界面处羟基自由基自发形成的观点提出质疑。
英文摘要
An alternative explanation is presented for recent reports that attribute sustained chemiluminescence (CL) and electrochemiluminescence (ECL) from electrogenerated microbubbles on steel or copper electrodes in aqueous luminol solutions (over 2-30 V range) to the spontaneous formation of hydroxyl radicals at the gas-water interface. Our experiments with a broad set of electrodes, viz., steel, copper, aluminium, and platinum, reveal that while microbubbles can be electrogenerated on all electrodes, CL is exhibited by steel and Cu only and not by Al and Pt. These observations establish that the gas-water interface of microbubbles is not the site for hydroxyl radical generation (else CL would be recorded in all cases). Complementary quantification of H2O2 in these experiments reveals its electrode dependence as follows: Al > Cu > Steel > Pt. This establishes that depending on the electrode, H2O2 forms first, and in some cases, hydroxyl radicals are observed (i.e., where CL/ECL is seen). Experiments with NMR and EPR spectroscopy revealed that: (i) H2O2 formation occurs only when O2 is present in water; and (ii) while steel and copper generate hydroxyl radicals through 1-electron reduction of H2O2, Al does not promote one-electron reduction of H2O2 to generate hydroxyl radicals, and Pt preferentially promotes disproportionation of H2O2 to H2O and O2. In fact, we demonstrate that H2O2 and hydroxyl radicals can be observed at specific metal-water interfaces even without microbubbles, confirming that the solid surface is the reactive site. Therefore, this work affords electrode-based predictions of whether or not electrogenerated microbubbles would yield CL in luminol solutions and calls into question the notion of spontaneous formation of hydroxyl radicals at gas-water interfaces.
