NSF-DFG Echem: Surface Stability and Oxygen Defect Chemistry of Pyrochlore and Related High-Performing Electrocatalysts for Oxygen Evolution Reaction

表面费米能是表征无贵金属电催化材料高活性和高稳定性的重要参数。为了验证这一假设，该项目将使用X射线光电子能谱法和原位样品处理来研究烧绿石电催化剂如Y2 Ru 2 O 7和RE 2 Ru 2 O 7（RE = Pr、Nd、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb和Lu）在水电解质中的析氧反应表面的费米能位置。界面形成与高和低功函数氧化物，如RuO 2和Sn掺杂的In 2 O3（ITO），以及氧化和还原处理将被用来评估的能带排列的电催化剂结合的限制的表面费米能。费米能的限制与Ru离子的价态变化有关，并决定了与电解质接触的催化剂的热力学稳定范围。将评估通过使用合适的掺杂剂将费米能限制在表面的稳定性和活性的潜在增强。该项目是在伊利诺伊大学厄巴纳-香槟分校领导下的NSF-DFG联合提案的一部分，其中Hong Yang教授负责样品合成和电催化表征，Nicola H.佩里进行缺陷化学分析。从XPS分析得到的结果将与缺陷特性进行比较，并用于开发稳定和高活性烧绿石光催化剂的组合物和掺杂概念。通过这一点，该项目将推进低温聚合物电解质膜（PEM）电解槽的水分解技术。

It is hypothesized that the surface Fermi energy is an important descriptor for a high activity and stability of noble-metal free electrocatalytic materials. To test this hypothesis, the project will study the Fermi energy position at the surfaces of pyrochlore electrocatalysts such as Y2Ru2O7 and RE2Ru2O7 (RE = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) for the oxygen evolution reaction in aqueous electrolytes using X-ray photoelectron spectroscopy with in situ sample processing. Interface formation with high and low work function oxides, such as RuO2 and Sn-doped In2O3 (ITO), as well as oxidizing and reducing treatments will be employed to assess the energy band alignment of the electrocatalysts in conjunction with the limits of the surface Fermi energy. The limitation of the Fermi energy is related to valence changes of the Ru ions and determines the thermodynamic stability range of the catalysts in contact with the electrolyte. A potential enhancement of stability and activity by confining the Fermi energy at the surface using suitable dopants will be assessed. The project is part of a joint NSF-DFG proposal under the lead of University of Illinois at Urbana-Champaign, where Prof. Hong Yang is responsible for sample synthesis and electrocatalytic characterization and Prof. Nicola H. Perry for defect chemistry analysis. The results obtained from the XPS analysis will be compared with defect properties and be used to develop composition and doping concepts for stable and highly active pyrochlore photocatalysts. By this, the project will advance water-splitting technology for low temperature polymer electrolyte membrane (PEM)-based electrolyzers.