Laser-Induced Graphene for Energy application
Tour, James M
Doctor of Philosophy
The rapidly increasing demand for clean energy has stimulated extensive research efforts on the renewable energy technologies, such as fuel cells, hydrogen and oxygen production from water splitting, and rechargeable metal-air batteries. The underlying chemical processes, including the oxygen evolution reaction (OER), hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR), generally suffer from sluggish reaction kinetics. Therefore, effective catalysts are necessary to facilitate the reactions. This thesis focuses on the development of laser-induced graphene (LIG) derived materials and catalysts for electrochemical energy storage devices. LIG is a 3D porous graphene material grown on a flexible substrate that is prepared by a one-step laser scribing process on commercial polyimide (PI) film. The LIG derived from PI is highly porous and is easily synthesized under ambient conditions in a scalable process. Chapter 1 discusses the oxidation of LIG by O2 plasma to form oxidized LIG, which boosts its performance in both OER and ORR resulting in an enhanced activity towards rechargeable Li-O2 battery. In Chapter 2, a distinctive re-lasing method was proposed to prepare metal oxide/LIG composites as efficient catalysts for water oxidation (OER). Unlike the conventional methods, such as solvo-/hydro-thermal, thermal pyrolysis or chemical vapor deposition processes, the re-lasing synthesizes the NiFe-based catalysts through a facile laser scribing process without any tedious procedures. Chapter 3 introduces a bifunctional catalyst Co3O4/LIG that was synthesized through a facile re-lasing process, showing OER and ORR activity comparable to noble metal-based catalysts in alkaline electrolyte. Furthermore, the Co3O4/LIG exhibited promising performance in Zn-air and Li-O2 batteries. Chapter 4 discusses ternary metal oxide/graphene hybrid catalysts by combining ORR-active Co/Mn with OER-active Ni and Fe species to promote the bifunctional activity all in an in situ formed LIG flexible film. These hybrid catalysts exhibit high catalytic activity and surpass the performance of precious metal Pt and RuO2 catalysts in Znair batteries and demonstrate applications in flexible Zn-air batteries that would be beneficial for wearable and flexible electronic devices. Chapter 5 discusses the performance of bifunctional OER/ORR catalysts MnNiFe/LIG (M111/LIG and M311/LIG, where the numbers reflect the relative molar ratio of Mn, Ni and Fe species) in Li-O2 and Li-air batteries without the presence of a redox mediator. The underlying mechanism in Li-O2 battery was investigated. Chapter 6 introduces the design of dual polymer gel electrolyte (DPGE). The combination of DPGE with a Mnbased catalyst enhance the performance of quasi-solid-state Li-O2 batteries.
LIG; OER; ORR; metal-air battery; energy storage