Rational construction of carbon quantum dots-zinc cobalt oxide heterostructure as bifunctional catalyst for oxygen evolution reaction and wastewater treatment

Semiconductor photocatalysts are promising for Oxygen evolution reaction (OER) and also for reducing organic pollutants in wastewater. However, their limited activity under UV light and the fast recombination of electron-hole pairs, hinder their utilization in wastewater treatment. To address these challenges a novel photocatalyst based on carbon quantum dots (CQDs) supported Zinc–Cobalt Oxide (ZnCo₂O₄) was developed, which demonstrated enhanced photocatalytic efficiency. Experimental findings indicated that 0.7 CQDs/ZnCo₂O₄ exhibited superior photocatalytic performance compared to ZnCO₂O₄ and CQDs/ZnCO₂O₄ composites materials, achieving over 100 and 96 % decomposition of methylene blue (MB) and methylene orange (MO) dyes after 50 and 140 min under UV light. The enhanced performance of 0.7 CQDs/ZnCo₂O₄ can be attributed to the charge transfer rate and synergistic effect between the coupled CQDs and ZnCo₂O₄. Moreover, studies with radical scavengers reveal that •O₂, •OH, and h⁺ play crucial roles in the breakdown of MB and MO dyes. Furthermore, 0.7 CQDs/ZnCo₂O₄ displayed very low overpotential of 220 mV at 100 mA cm⁻² for OER activity with a robust durability for 250 h at 500 mA cm⁻².