Kluge Regina M, Psaltis Eleftherios, Haid Richard W, Hou Shujin, Schmidt Thorsten O, Schneider Oliver, Garlyyev Batyr, Calle-Vallejo Federico, Bandarenka Aliaksandr S
Physik-Department ECS, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany.
Catalysis Research Center TUM, Ernst-Otto-Fischer-Straße 1, 85748 Garching, Germany.
ACS Appl Mater Interfaces. 2022 May 4;14(17):19604-19613. doi: 10.1021/acsami.2c03604. Epub 2022 Apr 20.
For large-scale applications of hydrogen fuel cells, the sluggish kinetics of the oxygen reduction reaction (ORR) have to be overcome. So far, only platinum (Pt)-group catalysts have shown adequate performance and stability. A well-known approach to increase the efficiency and decrease the Pt loading is to alloy Pt with other metals. Still, for catalyst optimization, the nature of the active sites is crucial. In this work, electrochemical scanning tunneling microscopy (EC-STM) is used to probe the ORR active areas on PtGd and PtPr in acidic media under reaction conditions. The technique detects localized fluctuations in the EC-STM signal, which indicates differences in the local activity. The experiments, supported by coordination-activity plots based on density functional theory calculations, show that the compressed Pt-lanthanide (111) terraces contribute the most to the overall activity. Sites with higher coordination, as found at the bottom of step edges or concavities, remain relatively inactive. Sites of lower coordination, as found near the top of step edges, show higher activity, presumably due to an interplay of strain and steric hindrance effects. These findings should be vital in designing nanostructured Pt-lanthanide electrocatalysts.
对于氢燃料电池的大规模应用，必须克服氧还原反应（ORR）缓慢的动力学。到目前为止，只有铂（Pt）族催化剂表现出足够的性能和稳定性。一种提高效率并降低铂负载量的知名方法是将铂与其他金属合金化。然而，对于催化剂的优化而言，活性位点的性质至关重要。在这项工作中，电化学扫描隧道显微镜（EC-STM）被用于探测在反应条件下酸性介质中PtGd和PtPr上的ORR活性区域。该技术检测EC-STM信号中的局部波动，这表明局部活性的差异。基于密度泛函理论计算的配位活性图支持的实验表明，压缩的铂-镧系元素（111）平台对整体活性贡献最大。在台阶边缘底部或凹处发现的具有较高配位的位点仍然相对不活跃。在台阶边缘顶部附近发现的配位较低的位点显示出较高的活性，这可能是由于应变和空间位阻效应的相互作用。这些发现对于设计纳米结构的铂-镧系元素电催化剂至关重要。
