Spatial Identification of Mott–Schottky Effect at Electrocatalytic Pd/Metal Oxide Interfaces for the Oxygen Reduction Reaction

To elucidate the microstructure and charge transfer behavior at the interface of Pd/metal oxide semiconductor (MOS) catalysts and systematically explore the crucial role of the Mott-Schottky effect in the oxygen reduction reaction (ORR) electrocatalysis process, this study established a testing system for spatially identifying Mott-Schottky effects and electronic properties at Pd/MOS interfaces, leveraging highly sensitive Kelvin probe force microscopy (KPFM). This system enabled visualization and quantification of the surface potential difference and Mott-Schottky barrier height (Φ_SBH) at the Pd/MOS heterojunction interfaces. Furthermore, a series of Pd/MOS Mott-Schottky catalysts were constructed based on differences in work functions between Pd and n-type MOS. The abundant oxygen vacancies in these catalysts facilitated the adsorption and activation of oxygen molecules. Notably, the intensity of the built-in electric field in the Pd/MOS Mott-Schottky catalysts was calculated through surface potential and zeta potential analysis, systematically correlating the Mott-Schottky effect at the heterojunction interface of Pd/MOS with ORR activity and kinetics. By comprehensively exploring the correlation between the Mott-Schottky effect and ORR performance in Pd/MOS catalysts using the KPFM testing system, this study provides necessary tools and approaches for a deep understanding of heterogeneous interface charge transfer mechanisms, as well as for optimizing catalyst design and enhancing ORR performance.