TiO2-modified g-C3N4 nanocomposite for photocatalytic degradation of organic dyes in aqueous solution

Ntakadzeni Madima; Kebede K Kefeni; Shivani B Mishra; Ajay K Mishra

doi:10.1016/j.heliyon.2022.e10683

TiO₂-modified g-C₃N₄ nanocomposite for photocatalytic degradation of organic dyes in aqueous solution

Heliyon. 2022 Sep 18;8(9):e10683. doi: 10.1016/j.heliyon.2022.e10683. eCollection 2022 Sep.

Authors

Ntakadzeni Madima¹, Kebede K Kefeni¹, Shivani B Mishra^{2

3}, Ajay K Mishra^{2

3

4}

Affiliations

¹ Institute for Nanotechnology and Water Sustainability (iNanoWS), College of Science, Engineering and Technology, University of South Africa, Florida Science Campus, Florida, Roodepoort, Johannesburg, 1709, South Africa.
² College of Pharmaceutical and Chemical Engineering, Hebei University of Science and Technology, Shijiazhuang, 050018, China.
³ Academy of Nanotechnology and Wastewater Innovations, Johannesburg, South Africa.
⁴ Department of Chemistry, Durban University of Technology, Steve Biko Road, 4001, Durban, South Africa.

Abstract

In the current study, a direct S-scheme titanium dioxide/graphitic carbon nitride (TiO₂/g-C₃N₄) heterojunction structure was fabricated via simultaneous calcination of TiO₂ precursors and g-C₃N₄. Guava leaf extract was utilized as a reductant for TiO₂ production through a green synthetic method, and g-C₃N₄ was prepared by thermal decomposition of melamine. The pristine and nanocomposite photocatalysts were characterized by XRD, FTIR, BET, TGA, HRTEM, UV-vis DRS, and PL to elucidate their physicochemical properties. The photocatalytic activity of synthesized photocatalysts was examined through the degradation of rhodamine B (RhB) and methylene blue (MB) dyes under simulated solar light irradiation. The nanocomposite exhibited commendable photocatalytic performances with 96% degradation efficiency of RhB attained in 120 min and 95% degradation efficiency of MB achieved in 150 min. The enhanced photocatalytic activities were attributable to visible light-harvesting characteristics and the formation of an S-scheme heterojunction system between two catalysts which promotes interfacial charge separation efficiency and longer charge carrier lifespan. After 4 consecutive cycles, the degradation efficiencies of both RhB and MB remained above 85%. According to the trapping experiments, OH^• and O₂ ^•- radicals were critical in the degradation of RhB, while h⁺ and O₂ ^•- radicals were dominant in the degradation of MB. The nanocomposite was also tested for elution of actual water pollutants by combining two dyes, and above 90% degradation efficiencies were achieved for both dyes after 240 min.

Keywords: Green synthesis; Nanocomposite; Photocatalytic degradation; Radical scavenger.