UC Santa Cruz

Electrochemical water splitting is widely recognized as a promising strategy for sustainable hydrogen production, where the development of efficient, stable, and cost-effective electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is of critical importance. Among various transition metal catalysts, ruthenium (Ru)-based materials have attracted significant attention due to their remarkable catalytic activity, tunable electronic structure, and relatively lower cost compared to platinum-group metals such as Pt and Ir. However, challenges remain in optimizing Ru utilization efficiency, regulating its electronic configuration, and achieving rapid and scalable synthesis of high-performance bifunctional catalysts. This dissertation focuses on the rational design, rapid synthesis, and mechanistic understanding of Ru-based nanostructured electrocatalysts for efficient electrochemical water splitting. Chapter 1 introduces the fundamental principles of electrochemical water splitting, with emphasis on HER and OER mechanisms, thermodynamic and kinetic limitations, and current challenges in catalyst development. Particular attention is given to the catalytic properties of Ru-based materials and their structure–activity relationships. Chapter 2 investigates the impacts of ruthenium valence states on HER performance using ruthenium ion-complexed graphitic carbon nitride/reduced graphene oxide (Ru–CN/rGO) nanosheets. By controlling the oxidation state of Ru species, the electronic structure and active sites of the catalyst were effectively tuned. The optimized catalyst exhibited enhanced XIII HER activity and stability, demonstrating the crucial role of Ru valence modulation in improving catalytic efficiency. Chapter 3 presents a rapid synthesis strategy for ruthenium–copper (Ru–Cu) nanocomposites as high-performance bifunctional electrocatalysts for overall water splitting. The introduction of Cu significantly modulated the electronic structure of Ru and promoted synergistic interactions between the two metals. The resulting Ru–Cu nanocomposites exhibited excellent catalytic activity toward both HER and OER, achieving low overpotentials and superior durability, highlighting the effectiveness of bimetallic engineering in enhancing bifunctional catalytic performance. Chapter 4 describes a rapid synthesis approach for carbon-supported Ru–RuO₂ heterostructures designed for efficient electrochemical water splitting. The formation of metal–oxide heterointerfaces provided abundant active sites and facilitated charge transfer, leading to enhanced catalytic kinetics for both HER and OER. The optimized Ru–RuO₂/C catalyst demonstrated remarkable activity and long-term stability under practical operating conditions, underscoring the advantages of heterostructure engineering. Overall, this dissertation establishes systematic strategies for tailoring the electronic structure, composition, and interfacial properties of Ru-based catalysts through valence-state control, bimetallic design, and heterostructure engineering. The developed rapid synthesis methods enable scalable production of high-performance electrocatalysts, while mechanistic insights into structure–activity relationships provide valuable guidance for the rational design of next-generation catalysts. These findings contribute to advancing the development of efficient and economically viable electrocatalysts for sustainable hydrogen production and renewable energy conversion.