Defence Jiahui Zhu: "Ni-based Electrocatalysts for Water Oxidation and Beyond"
Promotors: 1st promotor: Prof Paolo Pescarmona, 2nd promotor:Dr Morales Hernández
Abstract: Water electrolysis represents a promising pathway for sustainable hydrogen production, particularly when coupled with renewable energy sources. Among existing technologies, alkaline water electrolysis (AWE) offers significant advantages in cost-effectiveness and catalyst flexibility; however, its efficiency is constrained by the sluggish oxygen evolution reaction (OER). This thesis focuses on the rational design and synthesis of Ni-based electrocatalysts with enhanced OER activity, durability, and scalability. First, a comprehensive introduction to water electrolysis fundamentals, performance metrics, and catalyst engineering strategies is presented. Subsequently, Fe-modified Ni₃S₂ nanostructures grown on Ni foam are demonstrated to achieve exceptional OER activity, requiring only 230 mV to reach 100 mA·cm⁻² and maintaining 500 mA·cm⁻² for 100 h, attributed to the synergistic formation of conductive Ni₃S₂ scaffolds and surface NiFe (oxy)hydroxides. Extending this approach, Fe-incorporated Ni₃Se₂ nanowires exhibit optimized performance (250 mV at 100 mA·cm⁻²) and scalability in a 5 cm² AEM electrolyzer. Furthermore, a simple, low-energy acid-etching strategy was developed to activate commercial NiFe foams, yielding catalysts with excellent activity (240 mV at 100 mA·cm⁻²) and long-term stability, emphasizing the critical role of surface chemistry tuning. Beyond water splitting, Fe-modified and pristine chalcogenides were evaluated for 5-hydroxymethylfurfural (5-HMF) oxidation, revealing that Fe-free Ni₃Se₂ catalysts achieved superior performance with 96% FDCA yield and 92% Faradaic efficiency. Overall, this work provides mechanistic and structural insights into Ni-based catalysts, highlighting how Fe incorporation, chalcogen identity, and scalable surface engineering collectively advance efficient and ultifunctional electrocatalytic systems for green hydrogen and biomass valorization.