Role of Sulfur in Enhancing UV-Light Absorption and Photoelectrochemical Performance of ZnO/N,S-doped CQDs Nanocomposite

Afifah Salma Giasari, Rifky Adhia Pratama, Dr. Diana Rakhmawaty Eddy, Irkham, Muchammad Dhuhri Adzani, Natasha Fransisca, Uji Pratomo, Noto Susanto Gultom, Indriyati, Indah Primadona
https://doi.org/10.1002/slct.202404072

Abstract

The modification of ZnO, such as transforming it from 1-D to 3-D nanostructures or compositing it with carbon-based materials, has been extensively explored to enhance light energy harvesting and reduce electron-hole recombination-key limitations of ZnO. Herein, the effect of different composite materials, specifically nitrogen-doped carbon quantum dots (N-CQDs) and nitrogen, sulfur-doped carbon quantum dots (N,S-CQDs), on ZnO’s morphology and photocurrent response was studied. Various morphologies were synthesized on conductive glass substrate using a one-pot hydrothermal method, including flower-like structure for ZnO/N-CQDs (∼d = 0.9 µm) and multilayered microspheres for ZnO/N,S-CQDs (∼d = 1.1 µm). The inclusion of sulfur atoms in the composite resulted in a reduced bandgap value from 3.22 to 3.11 eV, along with enhanced light absorption efficiency and improved separation of photogenerated electron-hole pairs. Furthermore, the crystallinity of ZnO/N,S-CQDs was significantly enhanced compared to ZnO without sulfur doping. These improvements were reflected in the photoelectrochemical (PEC) measurements, where ZnO/N,S-CQDs showed a current density of 21.8 µA/cm² at 0.5 V (vs. Ag/AgCl), which is 5.5 times higher than that of ZnO/N-CQDs (4.0 µA/cm²). These findings demonstrate that sulfur doping improves photocatalytic efficiency, making 3D ZnO/N,S-CQDs a promising candidate for various UV-driven PEC applications.

Keywords: