Charge storage and electrocatalysis of the oxygen evolution reaction by copper zeolites: micro versus nanozeolites

In this study, Cu-exchanged X and Y zeolites were synthesized in both microcrystalline and nanocrystalline forms and evaluated as electrocatalysts for the oxygen evolution reaction (OER) in alkaline media. X-ray diffraction analysis and Fourier-transform infrared spectroscopy revealed somewhat decreased crystallinity of the nanozeolites, accompanied by a higher specific surface area determined by nitrogen sorption analysis. The results demonstrated that both the zeolite framework type and crystal size significantly influence the accessibility and activity of Cu catalytic sites. All samples produced anodic currents associated with oxygen evolution; however, pronounced differences in catalytic activity were observed. Among the investigated materials, nanocrystalline CuY (n-CuY) displayed the lowest onset potential and the highest current density, indicating the most favorable OER kinetics. Nyquist plots revealed lower charge-transfer resistance, supporting faster electron-transfer kinetics at the n-CuY electrode-electrolyte interface. Finally, exceptional long-term stability was observed during a 16-hour run. Nanocrystalline CuY emerged as the most promising candidate among the investigated materials, highlighting the potential to tailor Cu-exchanged zeolites as cost-effective electrocatalysts for alkaline oxygen evolution.