Exploration of the spin related reaction mechanisms of oxygen electrocatalysis

• Main Author: Chen, Ruixi
• Other Authors: XU Zhichuan, Jason
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2022
• Subjects: Science::Chemistry::Physical chemistry::Electrochemistry; Science::Chemistry::Physical chemistry::Catalysis
• Online Access: https://hdl.handle.net/10356/154992
• Institution: Nanyang Technological University

Exploring highly efficient catalysts for the oxygen evolution reaction (OER) is essential for water electrolysis. Cost-effective transition-metal oxides with reasonable activity are raising attention. This thesis presents in-depth studies to explore spin-dependent OER mechanisms for transition metal oxide catalysts and proposes a new rational design for highly efficient OER catalysts. This thesis firstly investigates the significance of spin channels for water oxidation. A layered antiferromagnetic inverse spinel oxide LiCoVO4, which possesses spin-polarized edge-shared Co2+ octahedra channels, is synthesized. I demonstrate that these spin-polarized channels facilitate spin-selective electron transfer during OER and promote triplet oxygen generation. Besides that, I design bi-magnetic core–shell nanoparticles (NPs) with different core sizes and shell thicknesses that mimic surface reconstructed catalysts to investigate the effect of magnetic domain structure on direct magnetic field induced OER catalytic activity enhancement phenomena. In these studies, I find that the interfacial FM–AFM coupling of these core-shell catalysts facilitates selective removal of electrons with spin direction opposing the magnetic moment of their FM cores, improving OER kinetics. Also, the FM core’s domain structure is critical for the spin-selective electron transport process. I, therefore, propose a magnetism/OER activity model that depends on two main parameters: interfacial spin coupling and domain structure. Lastly, I apply the findings from these studies to design a good OER catalyst, SmCo5/CoOxHy core-shell particle, for high temperature practical applications. It maintained the magnetic field induced OER activity enhancement even at an elevated temperature of 60 ºC. This catalyst’s unique property grants it huge potential to utilize spin-selective electron transfer, induced by the spin-pinning effect, in high temperature practical applications.