Deep understanding the formation of hollow ZnO@ZnS core-sheath heterojunction towards efficient CO2 photoreduction

• Published in: Separation and purification technology 2024-01, Vol.329, p.125228, Article 125228
• Main Authors: Ma, Xiaohong, Zheng, Jiajia, Jin, Huacheng, Zeng, Xi, Li, Danyang, You, Feifei, Qi, Jian, Yuan, Fangli
• Format: Article
• Language: English
• Subjects: CO2 photoreduction; Core-sheath heterojunction; Formation mechanism; Hollow structures; ZnO@ZnS
• ISSN: 1383-5866; 1873-3794
• DOI: 10.1016/j.seppur.2023.125228

Hollow ZnO@ZnS core-sheath heterojunction photocatalyst exhibits approximately 100% CO selectivity and excellent stability for CO2 reduction reaction, resulting from the hollow core-sheath structure enhancing light capture and absorption, exposing more effective active sites, as well as the heterostructure between ZnO and ZnS improving the separation efficiency of charge carriers. [Display omitted] •Hollow ZnO@ZnS core-sheath heterojunction was successfully synthesized by combining radio frequency thermal plasma and hydrothermal treatment technology.•The intermediate of hollow ZnO@ZnS core-sheath heterojunction was captured and the formation mechanism was proposed and verified.•The ZnO@ZnS photocatalyst with optimal S/Zn molar ratio exhibits approximately 100% CO selectivity and excellent stability.•The hollow core-sheath heterostructure can enhance light capture and absorption, expose more effective active sites and build a type-II heterojunction between ZnO and ZnS to improve the separation efficiency of charge carriers. The utilization of solar energy to convert CO2 into small energy molecules is a potential “carbon neutral” technology for CO2 emission reduction. However, the industrial application is significantly constrained due to the low reduction efficiency, complexity of the synthesis methods, and limitations in scaling up the catalyst materials. In this work, we have successfully designed and synthesized a series of hollow tubular ZnO@ZnS core-sheath heterostructured materials, by combining radio-frequency thermal plasma and hydrothermal treatment technologies. The S:Zn molar ratio, reaction time, and temperature were systematically investigated, and the morphology of intermediate products was successfully captured, which provided conclusive evidence for the proposed formation mechanism. Notably, the photocatalytic CO yield of the ZS0.5O hollow nanotube core-sheath composite is not only 3.20 or 4.03 times higher than that of the pure ZnO or ZnS, respectively, but also possesses excellent stability. By in-depth characterization, we found that the hollow core-sheath heterostructure enhances light capture and absorption, exposes more effective active sites, and builds a type-II heterojunction between ZnO and ZnS to enhance the separation efficiency of charge carriers. The synergy of these factors significantly improves the catalytic performance, offering new insights for photocatalytic, electrocatalytic, and photoelectrocatalytic CO2 reduction.