In-situ detection of active sites for carbon-based bifunctional oxygen reduction and evolution catalysis
In-situ detection of active sites for carbon-based bifunctional oxygen reduction and evolution catalysis
复制标题
DOI：
10.1016/j.electacta.2021.138285
复制
发表时间：
2021-04
影响因子：
6.6
通讯作者：
Richard W. Haid;Regina M. Kluge;T. Schmidt;A. Bandarenka
中科院分区：
文献类型：
--
作者：
Richard W. Haid;Regina M. Kluge;T. Schmidt;A. Bandarenka
由于其可用性和电化学多功能性，碳基电极正成为燃料电池和金属-空气电池的电催化剂的越来越受欢迎的选择。此外，它们作为碱性介质中的氧还原和析氧反应（ORR/OER）的双功能催化剂显示出巨大的潜力。然而，为了与最先进的催化剂竞争，需要深入了解活性位点的性质和反应条件下的表面稳定性。在这里，我们提出了一个原则的研究高度取向热解石墨（HOPG），在0.1 M KOH的ORR和OER条件下的表面行为进行评估。我们在电化学扫描隧道显微镜（n-EC-STM）中使用噪声分析来监测和比较ORR和OER活性位点，分辨率可达纳米级。此外，可以在操作期间评估表面退化。我们发现，接近各自的反应开始，步骤网站和缺陷是积极的ORR和OER。梯田场地基本上是不活跃的，只有在更高的潜力时才参与OER。这可能意味着碳的腐蚀。然而，由于所观察到的表面结构在我们的实验中应用OER之前和之后保持不变，我们没有发现表面破坏的明确证据。这些基本的见解可以激发关于碳基催化剂的活性位点和稳定性以及碳载体结构的进一步研究，以发现将表面活性和稳定性调整到专用目的的方法。
Due to their availability and electrochemical versatility, carbon-based electrodes are becoming an increasingly popular option as electrocatalysts for fuel cells and metal-air batteries. Additionally, they show great potential as bifunctional catalysts for the oxygen reduction and evolution reactions (ORR/OER) in an alkaline medium. However, to compete with state-of-the-art catalysts, the nature of the active sites and the surface stability under reaction conditions need to be understood in depth. Here, we present a principle study on highly oriented pyrolytic graphite (HOPG), evaluating the surface behavior under both ORR and OER conditions in 0.1 M KOH. We use noise analysis in electrochemical scanning tunneling microscopy (n-EC-STM) to monitor and compare ORR and OER active sites with resolution down to the nanoscale. Furthermore, surface degradation can be evaluated during the operation. We find that close to the respective reaction onset, step sites and defects are active for both ORR and OER. Terraces sites are largely inactive and only become involved in the OER at higher potentials. This could imply corrosion of the carbon. However, since the observed surface structures remain unaltered before and after applying the OER in our experiments, we find no clear evidence of surface destruction. These fundamental insights could inspire further research concerning the active sites and stability of carbon-based catalysts as well as carbon support structures, to discover ways to tune the surface activity and stability to the dedicated purpose.