(Photo)electrochemical Water Oxidation: From Catalysis to Functional Device

Sammanfattning: The key challenge within artificial photosynthesis is achieving efficient electro- or photo-driven water oxidation catalysis, a necessary process to supply the protons for the reduction reactions, thereby enabling solar fuel production. To facilitate efficient water (photo)electrolysis for solar fuel production, this thesis focuses on two aspects: 1) elucidating the O-O bond formation mechanism and developing efficient, stable, and economical water oxidation catalysts (WOCs); 2) exploring stable, low-cost, light-absorbing photoanode materials that have suitable band structures and excellent charge diffusion properties.Chapter 1 provides an overview of the development of homogeneous and heterogeneous WOCs, with a particular emphasis on the catalytic mechanisms. Subsequently, it introduces the advancements in light-harvesting materials for photoelectrochemical cells and highlights the progress in the burgeoning field of lead halide perovskite-based photoanodes.Chapter 2 clarifies the physical and electrochemical characterization methodologies, along with the protocols employed for mechanistic investigations in this thesis.Chapter 3 introduces a host-guest complex, self-assembled through Co2+ and cucurbit[5]uril (CB[5]), as a supramolecular WOC. This catalyst, Co@CB[5], was immobilized on indium tin oxide substrate and BiVO4 photoanode for electrochemical and photoelectrochemical water oxidation. The role of Co@CB[5] in interfacial charge transfer is investigated by spectroscopic and electrochemical studies.Chapter 4 reports a molecularly well-defined heterogeneous WOC with aza-fused, π-conjugated microporous polymer coordinated single cobalt sites (Aza-CMP-Co). Integrating experimental and theoretical results, this work highlights the significance of electrolyte pH and the role of regulating the intramolecular hydroxyl nucleophilic attack pathway in enhancing water oxidation activity.Chapter 5 presents a stable formamidinium lead bromide (FAPbBr3) photoanode for water oxidation to achieve an exceptionally low onset potential. Theoretical calculations and spectroscopic characterizations reveal the origin of low onset potential, which offers pivotal insights in guiding the development of photovoltaic material-based photoelectrodes for solar fuel applications.