Effect mechanism of copper ions on photocatalytic activity of TiO2/graphene oxide composites for phenol-4-sulfonic acid photodegradation

Jia-Hao Shen; Miao-Miao Li; Lian-Feng Chu; Cui-Xiang Guo; Ya-Jun Guo; Ya-Ping Guo

doi:10.1016/j.jcis.2020.10.121

Effect mechanism of copper ions on photocatalytic activity of TiO₂/graphene oxide composites for phenol-4-sulfonic acid photodegradation

J Colloid Interface Sci. 2021 Mar 15:586:563-575. doi: 10.1016/j.jcis.2020.10.121. Epub 2020 Nov 3.

Authors

Jia-Hao Shen¹, Miao-Miao Li¹, Lian-Feng Chu¹, Cui-Xiang Guo¹, Ya-Jun Guo¹, Ya-Ping Guo²

Affiliations

¹ The Education Ministry Key Lab of Resource Chemistry, Shanghai Key Laboratory of Rare Earth Functional Materials, Shanghai Normal University, Shanghai 200234, PR China.
² The Education Ministry Key Lab of Resource Chemistry, Shanghai Key Laboratory of Rare Earth Functional Materials, Shanghai Normal University, Shanghai 200234, PR China. Electronic address: ypguo@shnu.edu.cn.

PMID: 33190833
DOI: 10.1016/j.jcis.2020.10.121

Abstract

Organic pollutants in electroplating wastewater can be removed by photodegradation, however the effect mechanism of heavy metal ions on photocatalytic activity still remains unknown. Herein, we firstly reported the self-assembly synthesis of titanium dioxide/reduced graphene oxide (TiO₂/rGO) composites for phenol-4-sulfonic acid (PSA) removal, and investigated the effects of Cu²⁺ ions on photocatalytic efficiency. During the self-assemble process, rGO nanosheets were connected together to form network macropores, and simultaneously induced the deposition of hierarchically nanostructured TiO₂ microspheres. The synergetic effects of TiO₂ microspheres and rGO nanosheets improved the photocatalytic activity by enhancing light adsorption ability, stabilizing electron-hole separation and decreasing band gap energy. The Cu²⁺ ions in wastewater showed positive and negative effects on PSA photodegradation. In the photocatalytic reaction, the electron-induced reduction reaction of Cu(II) into Cu(0) or Cu(I) took place, which inhibited electron-hole recombination and thus enhanced photocatalytic activity. However, the high chemical stability of PSA-Cu(II) complex compounds held back PSA photodegradation. The appropriate concentrations of Cu²⁺ ions at around 25 mg/L accelerated PSA photodegradation over TiO₂/rGO composites. The PSA degradation into CO₂ and H₂O was performed by using hydroquinone, benzoquinone and maleic acid as degradation intermediates. Hence, TiO₂/rGO composites are novel multifunctional photocatalysts to purify electroplating wastewater.

Keywords: Aerogel; Copper ions; Photodegradation; Reduced graphene oxide; Titanium dioxide.