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

• Published in: International journal of hydrogen energy Vol. 73; pp. 351 - 361
• Main Authors: Zaman, Fakhr uz, Iqbal, Sikandar, Saeed, Azhar, Muhammad, Fawad, Ghani, Usman, Sammed, Khan Abdul, Ali, Atif Mossad, Khandy, Shakeel Ahmad, Boakye, Felix Ofori
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 04-07-2024
• Subjects: Bifunctional catalyst; CQDs/ZnCoO4 MSs; Organic dyes; Oxygen evolution reaction; Photocatalytic degradation; Photocatalytic degradation; Bifunctional catalyst; Oxygen evolution reaction; CQDs/ZnCoO4 MSs; Organic dyes
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2024.06.066

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.
•CQDs-decorated ZnCo2O4 Mss was developed by facile impregnation-thermal methode.•The enhanced catalytic activity of CQDs/ZnCo2O4 is due to the n-p junction, which generatesholes, ●OH, and ●O2−.•Optimized 0.70 CQDs/ZnCo2O4 achieves nearly100% MB degradation in 50 min.•The photocatalytic degradation mechanism of CQDs/ZnCo2O4 MSs enhanced charge separation and improve overall photocatalytic activity.