부산대학교 도서관

ABSTRACTAs the world faces climate change and energy shortages due to increasing dependence on fossil fuels, the need for sustainable and reliable energy solutions has become more critical than ever. Renewable energy sources like solar, wind, and hydropower have shown great promise, but their intermittent nature calls for advanced energy conversion and storage technologies. Hydrogen energy, with its clean and sustainable profile, emerges as an ideal candidate for storing and utilizing energy from renewables. Proton exchange membrane water electrolysis (PEMWE) is a particularly promising method for hydrogen production, offering significant advantages over traditional alkaline water electrolysis (AWE) due to its higher efficiency and purity of hydrogen gas produced. However, PEMWE faces significant challenges, especially with the oxygen evolution reaction (OER) at the anode, necessitating the development of highly active, stable, and cost-effective electrocatalysts.This dissertation aims to enhance the performance of PEMWE systems by developing advanced acidic OER electrocatalysts and understanding their underlying mechanisms. The focus is on ruthenium-based catalysts, with particular emphasis on efforts to reduce the amount of ruthenium used. Reducing ruthenium content can significantly lower costs, making the technology more economically viable and favorable for commercialization. The research is structured into three main chapters, each addressing different aspects of catalyst development and optimization.In the first part of this dissertation, we investigate the enhancement of acidic OER catalytic performance through the introduction of 3d-transition metal, specifically copper (Cu), into metallic Ru-based catalysts. In this section, we explore into the structural and chemical properties of Ru alloying with Cu as an acidic OER catalyst. By introducing Cu into Ru, we aim to improve both the catalytic activity and stability. This section explores the synthesis methods, characterization techniques, and electrochemical measurements of the Cu-doped Ru catalysts. We analyze the effects of alloying Cu on the electronic structure and surface properties of metallic Ru, identifying the factors that lead to enhanced mass activity and stability. The findings highlight how introduction of Cu modulates the electronic structure of the active sites, reducing the overpotential and increasing the durability of the catalyst under acidic conditions.The next part focuses on the design and performance of facet-engineered RuO2-based OER catalysts. This section aims to optimize the catalytic performance by preferentially exposing specific crystal facets of RuO2. Different crystal facets exhibit varying catalytic behaviors due to their unique atomic arrangements and electronic properties. By engineering the exposure of these facets, we can enhance the overall catalytic performances. This part covers the synthesis of facet-engineered RuO2 catalysts, their structural characterization, and detailed electrochemical performance evaluation. We investigate the reaction mechanisms and trace the intermediates involved in the OER to understand the origins of the improved catalytic activity. The study reveals that certain facets of RuO2 have a higher density of active sites and more favorable reaction kinetics, contributing to the superior performance of these facet-engineered catalysts.In the final part, we take a holistic approach to the design of water electrolyzers by developing highly cost-effective catalysts tailored for each half-reaction: Ru-Co3O4/TF for acidic OER and CoP/CF for HER, while minimizing the use of noble metals. Through meticulous compositional and structural adjustments of spinel oxides, we achieved a notable enhancement in acidic OER performance by incorporating a small amount of Ru and modifying octahedral sites. Concurrently, employing phosphide-based catalysts synthesized on carbon-based substrates, we attained exceptional HER catalytic properties. This part discusses the integration of these optimized catalysts into a single electrolyzer, evaluating their performance through long-term stability tests.Through these three sections, this dissertation aims to address the critical challenges in the development of acidic OER electrocatalysts for PEMWE systems. By introducing Cu doping, engineering specific crystal facets, and further optimizing catalyst compositions for both HER and OER, we provide comprehensive strategies to enhance catalytic performance, stability, and cost-effectiveness. The insights gained from this research contribute to the advancement of practical and efficient hydrogen production technologies, supporting the broader goal of transitioning to sustainable and renewable energy sources.