Glancing Angle Deposition for Enhanced Oxygen Evolution Reaction

The oxygen evolution reaction (OER) presents a major kinetic challenge in alkaline water electrolysis. Nickel oxide (NiO) is generally accepted as a favorable material due to its abundance and stability, yet it also exhibits limited intrinsic catalytic activity. In this study, nanocolumnar NiO electrodes were fabricated using glancing angle deposition (GLAD), and key deposition parameters, film thickness, angle, and deposition rate, were systematically tuned to optimize OER performance. An overpotential of 311 mV at 10 mA/cm 2 was achieved for a 512 nm thick film deposited at 78° with an increasing‐rate profile. Interestingly, this performance peak coincided with a morphological transition zone within the nanocolumns, where growth dynamics likely promote a favorable defect landscape. In contrast, thicker films showed reduced activity, likely due to diminished defect density associated with further morphological evolution. Electrochemical cycling further enhanced performance via a self‐reconstruction process, forming branch‐like NiOOH/Ni(OH) 2 features and reducing the overpotential to 269 mV. These results highlight the impact of growth‐induced structural transitions and defect formation on catalytic performance, positioning GLAD as an effective platform for rational OER catalyst design.