Abstract Although the photocathodic protection technique is a green and effective metal protection method, the corrosion images monitoring of protected metals and the carrier dynamics of photoanode materials are rarely studied. In this work, we successfully collected the real-time images of carbon steel (CS) by using a particle video microscope probe and verified that the use of a hematite (α-Fe2O3) photoanode could realize the long-term protection of CS under visible-light illumination in a Na2S-containning alkaline solution. In the absence of Na2S, the irradiated α-Fe2O3 electrode could delay but not prevent CS corrosion. Time-resolved spectroscopy investigation revealed that rapid electron/hole recombination via a trapping-detrapping model and slow water oxidation kinetics with a rate constant of 10 s−1 were the main factors limiting the photocathodic protection efficiency of α-Fe2O3. Trap-state-mediated recombination could be reduced by accelerating interfacial hole transfer with Na2S as the hole scavenger. This effect reduced charge transfer resistance by three orders of magnitude relative to water oxidation. Our work showed that photocathodic protection behavior was determined not only by the relative position between the conduction band potential of α-Fe2O3 and the corrosion potential of CS but also by the reaction dynamics on the electrode surface. The acceleration of the interfacial charge transfer of α-Fe2O3 was proposed to be the key to effective photocathodic protection.

中文翻译：

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α-Fe2O3光阳极对碳钢光阴极保护的在线图像监测和动力学研究

摘要 虽然光阴极保护技术是一种绿色有效的金属保护方法，但对被保护金属的腐蚀图像监测和光阳极材料的载流子动力学研究却很少。在这项工作中，我们使用粒子视频显微镜探针成功采集了碳钢（CS）的实时图像，并验证了赤铁矿（α-Fe2O3）光阳极的使用可以实现可见光下对碳钢的长期保护。 - 在含 Na2S 的碱性溶液中进行光照。在没有 Na2S 的情况下，经过辐照的 α-Fe2O3 电极可以延迟但不能防止 CS 腐蚀。时间分辨光谱研究表明，通过捕获-去捕获模型的快速电子/空穴复合和速率常数为 10 s-1 的缓慢水氧化动力学是限制 α-Fe2O3 光阴极保护效率的主要因素。通过使用 Na2S 作为空穴清除剂加速界面空穴转移，可以减少陷阱态介导的复合。相对于水氧化，这种效应将电荷转移电阻降低了三个数量级。我们的工作表明，光阴极保护行为不仅取决于 α-Fe2O3 的导带电位与 CS 的腐蚀电位之间的相对位置，还取决于电极表面的反应动力学。