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

假设表面费米能是表征无贵金属电催化材料高活性和稳定性的重要描述符。为了验证这一假设，该项目将使用x射线光电子能谱和原位样品处理技术研究在水电解质中析氧反应中，Y2Ru2O7和RE2Ru2O7 （RE = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm， Yb和Lu）等焦绿盐电催化剂表面的费米能量位置。高功函数和低功函数氧化物（如RuO2和sn掺杂的In2O3 (ITO)）的界面形成，以及氧化和还原处理将用于评估电催化剂的能带排列，并结合表面费米能的极限。费米能的限制与钌离子的价态变化有关，决定了催化剂与电解质接触时的热力学稳定性范围。通过使用合适的掺杂剂限制表面的费米能来提高稳定性和活度的可能性将被评估。该项目是由伊利诺伊大学香槟分校（University of Illinois at Urbana-Champaign）领导的NSF-DFG联合提案的一部分，其中Yang Hong教授负责样品合成和电催化表征，Nicola H. Perry教授负责缺陷化学分析。XPS分析的结果将与缺陷性质进行比较，并用于开发稳定和高活性的焦绿盐光催化剂的组成和掺杂概念。由此，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.