The pressing demand for green hydrogen as a pillar of the energy transition underscores the urgent need for highly active, durable, and scalable components for alkaline water electrolysis (AWE). Among the critical components of AWE, the anode plays a defining role in determining overall system performance. Therefore, this thesis investigates the relationship between process parameters, anode structure, anode layer properties, and electrochemical performance of anodes during alkaline oxygen evolution reaction (OER). Although significant progress has been made in the development of active powder-based catalyst materials, the translation of their intrinsic activity into industrially relevant anodes remains limited. This is due to a poor understanding of structural features, wettability, mechanical stability, and interfacial oxygen–electrolyte behavior at the three-phase contact line. To address this, quantitative surface extrapolation, fabrication strategies, and wettability engineering are employed to elucidate the process‑structure‑property‑performance (PSPP) relationships of anodes. The first part of this thesis introduces Multistage data quantification (MSDQ), a statistical framework developed to enable the reliable extrapolation of micrometer‑scale surface measurements to macroscopic anode areas. This approach ensures statistical representativeness across heterogeneous anode surfaces. MSDQ is a key to achieve morphological control as it enables systematic characterization and comparison of surface features in full‑scale anodes. To establish and validate the MSDQ framework, two morphologically distinct yet chemically identical anode surfaces were fabricated. A commercially available cobalt oxide (Co₃O₄)-based catalyst ink was sprayed onto 1 × 1 cm² nickel supports. The morphological variation was induced by applying different ink flow rates during the coating process. A rough morphology was achieved with a high ink flow rate, while a smooth morphology was achieved with a low ink flow rate. Subsequently, MSDQ was applied to these two anodes, and key morphological descriptors were extracted, including surface roughness, roughness factor, and a newly defined homogeneity score obtained via atomic force microscopy. The application of MSDQ facilitated correlation of these descriptors with OER activity, measured via scanning droplet cell electrochemistry. The results revealed a strong correlation between the quantified surface features and electrocatalytic performance, thereby enabling the separation of intrinsic material activity from extrinsic structure-induced effects. This highlights the utility of MSDQ in systematically correlating structure–activity relationships of anodes. In the second part, structural features of nickel cobalt oxide (NCO) anode layers quantified via MSDQ are translated into macroscopic anode layer properties such as wettability and mechanical stability and are ultimately correlated with OER performance. To accomplish this, four anodes with comparable NCO loadings and chemical composition but distinct structures are fabricated by catalyst inks with varying solvent compositions (pure water vs. water–ethanol mixture) and drying temperatures during ultrasonic spray deposition (50 °C and 150 °C) onto a Ni support. Variation in solvent composition alters ink stability in a way that water‑based inks exhibit lower particle dispersion stability than water‑ethanol‑based inks, resulting in improved particle connectivity within the deposited layers, assessed from mechanical stability measurements. This enhanced particle connectivity reduced contact resistance and improved catalytic activity. Since mechanical stability is a critical aspect of anode layer performance, these measurements provide key insights into the structural stability and durability of the anodes. The second parameter, the drying temperature, results in distinct surface morphologies. At 50 °C, rough, hill-like structures, while at 150 °C, smoother concave formations with lower surface roughness are observed. Two-dimensional surface distribution data reveal that increased roughness correlates with enhanced lyophobicity, which facilitates bubble removal and thereby improves active site accessibility. These findings underscore the importance of structural control in influencing the wettability of the anode layer. Therefore, the third part broadens the investigation to include a detailed analysis of wettability, encompassing both lyophilic and lyophobic surface behaviors. Surface wettability is specifically tuned through binder selection (Sustainion vs. Nafion) and drying‑induced microstructural modification. Through a systematic investigation, the Sustainion-based anode layer exhibits pronounced super-lyophilicity (θ 150 °), which is characteristic of a Cassie‑Baxter wetting state. The super-lyophilic anode layer achieves the lowest overpotential among all tested anodes, with a reduction of 80 mV at 100 mA cm⁻². Post‑electrochemical characterization unravels a direct correlation between the wetting state and the extent of utilization of the anode layer and the dynamics of bubble detachment. The super-lyophilic anode layer facilitates full electrolyte penetration due to the rapid detachment of oxygen bubbles and the complete activation of the layer. In contrast, super‑lyophobic anode layers retain large non‑wetted regions of up to ~47 % due to the formation of larger bubbles and their adhesion to the surface resulting in only a partial contribution of the anode layer in the OER. These findings will enable rational design of high-performance anodes through systematic control of wettability across the full lyophilicity–lyophobicity spectrum. In summary, this thesis provides a comprehensive understanding of how fabrication protocols, structural features, and wetting behavior govern anode performance during OER. By combining quantitative surface analysis with coating conditions and the rational design of ink systems, the work establishes a versatile framework for developing structured, high-performance anodes. These findings advance the knowledge of AWE electrode design and at the same time, offer transferable strategies for a wide range of electrochemical technologies such as anion exchange membrane water electrolysis.
Adarsh Jain (Fri,) studied this question.