Electrocatalytic oxygen evolution on nano-CuOx modified electrodes: enhanced activity and stability through surface oxidation engineering

Developing low-cost and durable electrocatalysts for the oxygen evolution reaction (OER) remains a key challenge in sustainable electrochemical energy conversion. In this work, nanostructured copper oxide (CuOx) films were fabricated on glassy carbon (GC) electrodes via a simple electrodeposition followed by electrochemical oxidation. Structural characterization by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) confirmed the formation of a uniform CuO/Cu 2 O mixed-phase layer composed of nanosized aggregates with high surface roughness. Electrochemical measurements in 0.1 M NaOH revealed markedly enhanced OER activity for CuOx/GC compared with bare GC, requiring an overpotential of 380 mV to achieve 10 mA·cm −2 and exhibiting a Tafel slope of 85 mV.dec −1 . The superior activity was attributed to increased electrochemically active surface area, facilitated Cu(II)/Cu(III) redox transitions, and improved charge-transfer efficiency. The catalyst also demonstrated outstanding operational stability, retaining 95 % of its activity after 6 h of continuous operation. These results demonstrate that surface-engineered CuOx nanostructures serve as efficient, stable, and low-cost OER electrocatalysts suitable for alkaline electrolysis applications. Summary: The study reports the fabrication of nanostructured CuOx films on glassy carbon electrodes via electrodeposition and electrochemical oxidation, achieving a CuO/Cu 2 O mixed-phase with high surface area. These CuOx electrodes demonstrated excellent oxygen evolution reaction (OER) activity and stability in alkaline media, making them efficient, durable, and low-cost electrocatalysts for water electrolysis. • Facile electrochemical oxidation produces mixed-valence nano-CuOx films on GC. • Nanostructured CuOx enhances active-site density and electron transport. • Achieves low overpotential (η ₁₀ = 380 mV) and Tafel slope (85 mV·dec −1 ). • Excellent operational stability with 95 % activity retention after 6 h. • Competitive OER performance relative to state-of-the-art Cu-based catalysts.